Thermionic power systems were used in combination with various nuclear reactors (BES-5, TOPAZ) as electrical power supply on a number of Soviet military surveillance satellites between 1967 and 1988. See Kosmos 954 for more details. Although the priority for thermionic reactor use diminished as the US and Russian space programs were curtailed, research and technology development in thermionic energy conversion have continued. In recent years technology development programs for solar-heated thermionic space power systems were conducted.
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After the first demonstration of the practical arc-mode caesium vapor thermionic converter by V. Wilson in 1957, several applications of it were demonstrated in the following decade, including its use with solar, combustion, radioisotope and nuclear reactor heat sources. The application most seriously pursued, however, was the integration of thermionic nuclear fuel elements directly into the core of nuclear reactors for production of electrical power in space. The exceptionally high operating temperature of thermionic converters, which makes their practical use difficult in other applications, gives the thermionic converter decisive advantages over competing energy conversion technologies in the space power application where radiant heat rejection is required. Substantial thermionic space reactor development programs were conducted in the U.S., France and Germany in the period 1963–1973, and the US resumed a significant thermionic nuclear fuel element development program in the period 1983–1993.
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Although some applications had used earlier technologies such as the spark gap transmitter for radio or mechanical computers for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, and created the discipline of electronics. In the 1940s the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, more efficient, reliable and durable, and cheaper than thermionic tubes. From the mid-1960s, thermionic tubes were then being replaced with the transistor. Thermionic tubes still have some applications for certain high-frequency amplifiers.
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The type of device known as a thermionic tube or thermionic valve uses the phenomenon of thermionic emission of electrons from a heated cathode and is used for a number of fundamental electronic functions such as signal amplification and current rectification. Non-thermionic types, such as a vacuum phototube however, achieve electron emission through the photoelectric effect, and are used for such as the detection of light levels. In both types, the electrons are accelerated from the cathode to the anode by the electric field in the tube. The simplest vacuum tube, the diode invented in 1904 by John Ambrose Fleming, contains only a heated electron-emitting cathode and an anode.
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The most famous are his work on thermionic emission and the passage of current through a vacuum.
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Prototype combustion-heated thermionic systems for domestic heat and electric power cogeneration, and for rectification, have been developed.
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Later thermionic vacuum tubes, mostly miniature style, some with top cap connections for higher voltages A vacuum tube, an electron tube, valve (British usage) or tube (North America),John Algeo, "Types of English heteronyms", p. 23 in, Edgar Werner Schneider (ed), Englishes Around the World: General studies, British Isles, North America, John Benjamins Publishing, 1997 . is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as a thermionic tube or thermionic valve uses the phenomenon of thermionic emission of electrons from a hot cathode and is used for a number of fundamental electronic functions such as signal amplification and current rectification.
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The thermionic valve (a kind of vacuum tube) was invented in 1904 by the English physicist John Ambrose Fleming. He developed a device he called an "oscillation valve" (because it passes current in only one direction). The heated filament, or cathode, was capable of thermionic emission of electrons that would flow to the plate (or anode) when it was at a higher voltage. Electrons, however, could not pass in the reverse direction because the plate was not heated and thus not capable of thermionic emission of electrons.
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A tungsten filament in a low pressure mercury gas discharge lamp which emits electrons. To increase electron emission, a white thermionic emission mix coating is applied, visible on the central portion of the coil. Typically made of a mixture of barium, strontium, and calcium oxides, the coating is sputtered away through normal use, eventually resulting in lamp failure. In vacuum tubes and gas-filled tubes, a hot cathode or thermionic cathode is a cathode electrode which is heated to make it emit electrons due to thermionic emission.
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From a physical electronic viewpoint, thermionic energy conversion is the direct production of electric power from heat by thermionic electron emission. From a thermodynamic viewpoint, it is the use of electron vapor as the working fluid in a power-producing cycle. A thermionic converter consists of a hot emitter electrode from which electrons are vaporized by thermionic emission and a colder collector electrode into which they are condensed after conduction through the inter-electrode plasma. The resulting current, typically several amperes per square centimeter of emitter surface, delivers electrical power to a load at a typical potential difference of 0.5-1 volt and thermal efficiency of 5-20%, depending on the emitter temperature (1500-2000 K) and mode of operation.
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The symbol for an indirectly heated vacuum tube diode. From top to bottom, the element names are: plate, cathode, and heater. A thermionic diode is a thermionic-valve device consisting of a sealed, evacuated glass or metal envelope containing two electrodes: a cathode and a plate. The cathode is either indirectly heated or directly heated.
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In the 1940s, the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, more efficient, reliable, durable, safer, and more economical than thermionic tubes. Beginning in the mid-1960s, thermionic tubes were being replaced by the transistor. However, the cathode-ray tube (CRT) remained the basis for television monitors and oscilloscopes until the early 21st century. Thermionic tubes are still used in some applications, such as the magnetron used in microwave ovens, certain high-frequency amplifiers, and amplifiers that audio enthusiasts prefer for their "warmer" tube sound.
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Langmuir, I., "The Effect of Space Charge and Initial Velocities on the Potential Distribution and Thermionic Current between Parallel Plane Electrodes," Physical Review, Vol. 21, No. 4, 1923, pp. 419–435Langmuir, I., "The Effect of Space Charge and Residual Gases on Thermionic Currents in High Vacuum," Physical Review, Vol. 2, No. 6, 1913, pp. 450–486.
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The generic name "[thermionic] valve" used in the UK derives from the unidirectional current flow allowed by the earliest device, the thermionic diode emitting electrons from a heated filament, by analogy with a non-return valve in a water pipe.The Oxford Companion to the History of Modern Science, J. L. Heilbron, Oxford University Press 2003, 9780195112290, "valve, thermionic" The US names "vacuum tube", "electron tube", and "thermionic tube" all simply describe a tubular envelope which has been evacuated ("vacuum"), has a heater and controls electron flow. In many cases, manufacturers and the military gave tubes designations that said nothing about their purpose (e.g., 1614). In the early days some manufacturers used proprietary names which might convey some information, but only about their products; the KT66 and KT88 were "kinkless tetrodes".
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FEAs offer a number of potential advantages over conventional thermionic cathodes, including low power consumption, instantaneous switching, and independence of current and voltage.
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Before transistors were developed, vacuum (electron) tubes (or in the UK "thermionic valves" or just "valves") were the main active components in electronic equipment.
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Consisted of Racal Recorders (Hythe, Southampton) and Racal Instruments (Burham, near Slough). Racal acquired Thermionic Products in 1967, creating Racal Thermionics, renamed Racal Recorders in 1977.
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However, cold cathode tubes have cathodes that emit electrons only due to the large voltage between the electrodes. The cathodes will be warmed by current flowing through them, but are not hot enough for significant thermionic emission. Because cold cathode lamps have no thermionic emission coating to wear out, they can have much longer lives than hot cathode tubes. This makes them desirable for long-life applications (such as backlights in liquid crystal displays).
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The nitrogen–phosphorus detector (NPD) is also known as thermionic specific detector (TSD) is a detector commonly used with gas chromatography, in which thermal energy is used to ionize an analyte. It is a type of flame thermionic detector (FTD), the other being the alkali flame-ionization detector (AFID also known as AFD). With this method, nitrogen and phosphorus can be selectively detected with a sensitivity that is 104 times greater than that for carbon.
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A modern dial tone could be heard during overseas telephone calls between Bennett and Lord Beaverbrook. Air-traffic control equipment under repair contained TO-3 transistors instead of thermionic valves.
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The result in both scanning and transmission electron microscopy is significantly improved signal-to-noise ratio and spatial resolution, and greatly increased emitter life and reliability compared with thermionic devices.
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This is called the space charge effect. In the limit of large current densities, J is given by the Child–Langmuir equation below, rather than by the thermionic emission equation above.
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It was completely revised in 1961 by his colleague James Lafferty. His research on thermionic emission is remembered in the form of the Richardson-Dushman equation. He died in Scotia, New York.
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It was also called a thermionic valve, vacuum diode, kenotron, and thermionic tube. This "Fleming Valve" was sensitive and reliable, and so it replaced the crystal diode used in receivers used for long-distance wireless communication. It had an advantage, that it could not be permanently injured or set out of adjustment by any exceptionally strong stray signal, such as those due to atmospheric electricity.Fleming, John Ambrose (1914) The Wonders of Wireless Telegraphy: Explained in Simple Terms for the Non-technical Reader.
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Cold electrodes can also spontaneously produce electron clouds via thermionic emission when small incandescent regions (called cathode spots or anode spots) are formed. These are incandescent regions of the electrode surface that are created by a localized high current. These regions may be initiated by field electron emission, but are then sustained by localized thermionic emission once a vacuum arc forms. These small electron-emitting regions can form quite rapidly, even explosively, on a metal surface subjected to a high electrical field.
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Vacuum emission from metals tends to become significant only for temperatures over . The term 'thermionic emission' is now also used to refer to any thermally-excited charge emission process, even when the charge is emitted from one solid-state region into another. This process is crucially important in the operation of a variety of electronic devices and can be used for electricity generation (such as thermionic converters and electrodynamic tethers) or cooling. The magnitude of the charge flow increases dramatically with increasing temperature.
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There are two types. One uses semiconductor, or less efficient metal, i.e. thermocouples, working on the principles of the Peltier-Seebeck effect. The other relies on vacuum tubes and the principles of thermionic emission.
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Amplifiers may be based on tube ("thermionic" or in the UK, "valve") or solid state (transistor) technology, or hybrid designs that use both technologies, typically by pairing a tube preamplifier with a transistor power amplifer.
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The scientific aspects of thermionic energy conversion primarily concern the fields of surface physics and plasma physics. The electrode surface properties determine the magnitude of electron emission current and electric potential at the electrode surfaces, and the plasma properties determine the transport of electron current from the emitter to the collector. All practical thermionic converters to date employ caesium vapor between the electrodes, which determines both the surface and plasma properties. Caesium is employed because it is the most easily ionized of all stable elements.
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A suppressor grid is a grid used in a thermionic valve (also called vacuum tube) to suppress secondary emission. A suppressor grid is also called the antidynatron grid, as it helps to reduce the dynatron effect.
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Thermionic valve equipment usually does not have the valves mounted on the PCB in order to avoid heat damage, but instead use PCBs for the wiring, achieving the economy of mass- produced PCBs without the heat damage.
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A note from eulogy at the Centenary celebration of the invention of the thermionic valve: :One century ago, in November 1904, John Ambrose Fleming FRS, Pender Professor at UCL, filed in Great Britain, for a device called the Thermionic Valve. When inserted together with a galvanometer, into a tuned electrical circuit, it could be used as a very sensitive rectifying detector of high frequency wireless currents, known as radio waves. It was a major step forward in the 'wireless revolution'. > In November 1905, he patented the "Fleming Valve" ().
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Pam, D. (1977),The New Enfield: Stories of Enfield Edmonton and Southgate, a Jubilee History, London Borough of Enfield Libraries, Arts & Entertainment Dept In 1916, Ediswan set up the UK's first radio thermionic valve factory at Ponders End. This area, with nearby Brimsdown subsequently developed as a centre for the manufacture of thermionic valves, cathode ray tubes, etc., and nearby parts of Enfield became an important centre of the electronics industry for much of the 20th century. Ediswan became part of British Thomson-Houston and Associated Electrical Industries (AEI) in the late 1920s.
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The Royal Radar Establishment Automatic Computer, or the RREAC, was an early solid-state computer in 1962. It was made with transistors; many of Britain's previous experimental computers used the thermionic valve, also known as a vacuum tube.
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Historically, voltage has been referred to using terms like "tension" and "pressure". Even today, the term "tension" is still used, for example within the phrase "high tension" (HT) which is commonly used in thermionic valve (vacuum tube) based electronics.
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The work function is important in the theory of thermionic emission, where thermal fluctuations provide enough energy to "evaporate" electrons out of a hot material (called the 'emitter') into the vacuum. If these electrons are absorbed by another, cooler material (called the collector) then a measurable electric current will be observed. Thermionic emission can be used to measure the work function of both the hot emitter and cold collector. Generally, these measurements involve fitting to Richardson's law, and so they must be carried out in a low temperature and low current regime where space charge effects are absent.
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There are three active electron emission technologies usually considered for EDT applications: hollow cathode plasma contactors (HCPCs), thermionic cathodes (TCs), and field emitter arrays (FEAs). System level configurations will be presented for each device, as well as the relative costs, benefits, and validation.
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Dekker, A.J., "Thermionic Emission," McGraw Hill Access Science Encyclopedia, Vol. 2004, No. 5 / 3, 2002, pp. 2. Once the electrons are thermionically emitted from the TC surface they require an acceleration potential to cross a gap, or in this case, the plasma sheath.
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Paraset Mk. 7 at Bletchley Park museum Hand-made replica "Paraset" The Paraset was a small, low-power, thermionic valve CW morse code-only radio transmitter- receiver supplied to the resistance groups in France, Belgium and the Netherlands during World War II.
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The Rocket and the Reich: Peenemünde and the Coming of the Ballistic Missile Era. New York: The Free Press. p. 106.. The Tommy Flowers-built Colossus (1943) and the Atanasoff–Berry Computer (1942) used thermionic valves (vacuum tubes) and binary representation of numbers.
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The TOPAZ nuclear reactor is a lightweight nuclear reactor developed for long term space use by the Soviet Union. Cooled by liquid metal, it uses a high- temperature moderator containing hydrogen and highly enriched fuel and produces electricity using a thermionic converter.
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The first vacuum tube used in radio was the thermionic diode or Fleming valve, invented by John Ambrose Fleming in 1904 as a detector for radio receivers. It was an evacuated glass bulb containing two electrodes, a heated filament and a plate (anode).
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A pentode is an electronic device having five active electrodes. The term most commonly applies to a three-grid vacuum tube (thermionic valve), which was invented by the Dutchman Bernhard D.H. Tellegen in 1926.Okamura, Sōgo (1994). History of Electron Tubes, p.
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Campbell originally studied a problem of random sums motivated by understanding thermionic noise in valves, which is also known as shot-noise. Consequently, the study of random sums of functions over point processes is known as shot noise in probability and, particularly, point process theory.
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A regenerative circuit is an amplifier circuit that employs positive feedback (also known as regeneration or reaction).S. W. Amos, R. S. Amos, Newnes Dictionary of Electronics, 4th ed., London, U. K.: Newnes, 1999, p. 265, 269 E. Williams, Thermionic Valve Circuits, 4th ed.
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In initial discussions, it was unclear that TOPAZ and the somewhat similar YENISEI reactors were different systems, and when the existence of the two Russian thermionic reactors became generally known, US personnel began referring to TOPAZ as TOPAZ-I and YENISEI as TOPAZ-II.
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Schematic symbol used in circuit diagrams for a vacuum tube, showing control grid The control grid is an electrode used in amplifying thermionic valves (vacuum tubes) such as the triode, tetrode and pentode, used to control the flow of electrons from the cathode to the anode (plate) electrode. The control grid usually consists of a cylindrical screen or helix of fine wire surrounding the cathode, and is surrounded in turn by the anode. The control grid was invented by Lee De Forest, who in 1906 added a grid to the Fleming valve (thermionic diode) to create the first amplifying vacuum tube, the Audion (triode).
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Thermionic (vacuum-tube) diodes and solid-state (semiconductor) diodes were developed separately, at approximately the same time, in the early 1900s, as radio receiver detectors. Until the 1950s, vacuum diodes were used more frequently in radios because the early point-contact semiconductor diodes were less stable. In addition, most receiving sets had vacuum tubes for amplification that could easily have the thermionic diodes included in the tube (for example the 12SQ7 double diode triode), and vacuum-tube rectifiers and gas-filled rectifiers were capable of handling some high-voltage/high- current rectification tasks better than the semiconductor diodes (such as selenium rectifiers) that were available at that time.
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Scaled - down model of Topaz reactor The first thermionic converter reactors were discussed by scientists at the Los Alamos Scientific Laboratory (LASL) in 1957. Following the visit of Soviet scientists to LASL in 1958, they carried out tests on TI systems in 1961, initially developing the single cell ENISY reactor (also known as TOPAZ-II). Work was carried out by the Kurchatov Institute of Atomic Energy and the Central Bureau for Machine Building to develop the multi-cell TOPAZ (also known as TOPAZ-I), a Russian acronym for "Thermionic Experiment with Conversion in Active Zone". It was first ground tested in 1971, when its existence was acknowledged.
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Grundig started as a typical German company in 1945. Its early notability was due to Grundig radio. Max Grundig, a radio dealer, built a machine called "Heinzelmann," which was a radio that did not use thermionic valves. The first of the same was named the 'Weltklang'.
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LaB6 is an inert refractory compound, used in hot cathodes because of its low work function which gives it a high rate of thermionic emission of electrons; YB66 crystals, grown by an indirect-heating floating zone method, are used as monochromators for low-energy synchrotron X-rays.
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12AE10 Compactron tube (a dual pentode), made by GE Compactrons are a type of thermionic valve, or vacuum tube, which contain multiple electrode structures packed into a single enclosure. They were designed to compete with early transistor electronics and were used in televisions, radios, and similar roles.
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During the 1920s, Hull also was a major contributor to the development of gas-filled electron tubes at the GERL. He discovered how to protect thermionic cathodes from rapid disintegration under ion bombardment. This discovery enabled the successful development of hot- cathode thyratrons (gaseous triodes) and phanotrons (gaseous diodes).
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Vacuum tube diodes The thermionic vacuum tube diode, originally called the Fleming valve, was invented by John Ambrose Fleming in 1904 as a detector for radio waves in radio receivers, and evolved into a general rectifier. It consisted of an evacuated glass bulb with a filament heated by a separate current, and a metal plate anode. The filament emitted electrons by thermionic emission (the Edison effect), discovered by Thomas Edison in 1884, and a positive voltage on the plate caused a current of electrons through the tube from filament to plate. Since only the filament produced electrons, the tube would only conduct current in one direction, allowing the tube to rectify an alternating current.
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Since a "perfect vacuum" contains no charged particles, it normally behaves as a perfect insulator. However, metal electrode surfaces can cause a region of the vacuum to become conductive by injecting free electrons or ions through either field electron emission or thermionic emission. Thermionic emission occurs when the thermal energy exceeds the metal's work function, while field electron emission occurs when the electric field at the surface of the metal is high enough to cause tunneling, which results in the ejection of free electrons from the metal into the vacuum. Externally heated electrodes are often used to generate an electron cloud as in the filament or indirectly heated cathode of vacuum tubes.
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A thermionic generator is like a cyclic heat engine and its maximum efficiency is limited by Carnot's law. It is a low-Voltage high current device where current densities of 25-50 (A/squarecm) have been achieved at voltage from 1-2V. The energy of high temperature gases can be partly converted into electricity if the riser tubes of the boiler are provided cathode and anode of a thermionic generator with the interspace filled with ionized Caesium vapor. The surface property of primary interest is the work function, which is the barrier that limits electron emission current from the surface and essentially is the heat of vaporization of electrons from the surface.
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Fleming's first diodes The English physicist John Ambrose Fleming worked as an engineering consultant for firms including Edison Swan, Edison Telephone and the Marconi Company. In 1904, as a result of experiments conducted on Edison effect bulbs imported from the United States, he developed a device he called an "oscillation valve" (because it passes current in only one direction). The heated filament, was capable of thermionic emission of electrons that would flow to the plate (or anode) when it was at a positive voltage with respect to the heated cathode. Electrons, however, could not pass in the reverse direction because the plate was not heated and thus not capable of thermionic emission of electrons.
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A thermionic converter consists of a hot electrode, which thermionically emits electrons over a space-charge barrier to a cooler electrode, producing a useful power output. Caesium vapor is used to optimize the electrode work functions and provide an ion supply (by surface ionization) to neutralize the electron space charge.
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Non-thermal converters extract energy from emitted radiation before it is degraded into heat. Unlike thermoelectric and thermionic converters their output does not depend on the temperature difference. Non-thermal generators can be classified by the type of particle used and by the mechanism by which their energy is converted.
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This was cooled by liquid sodium-potassium, NaK, metal, it used a high-temperature moderator containing hydrogen and highly enriched uranium fuel. It produced electricity using a thermionic converter. It had a Plazma-2 SPT electric engine. Its mission was to search the oceans for naval and merchant vessels, using radar.
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He joined the General Electric Company (UK) research laboratory, where he remained for the rest of his career, working on thermionic valves. He lived in Penn, Buckinghamshire and was a noted philanthropist using the royalty income he received from the Haber patent. His two sons were both killed during World War II.
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This avoided the cost of a large high voltage mains supply (50 or 60 Hz) transformer. This type of circuit was used for thermionic valve (vacuum tube) technology. It was inefficient and produced a lot of heat which led to premature failures in the circuitry. Although failure were common, it was easily repairable.
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The electrons used to provide the synchrotron light are first produced at the electron gun, by thermionic emission from a heated metal cathode. The emitted electrons are then accelerated to an energy of 90 keV (kilo-electron volts) by a 90 kilovolt potential applied across the gun and make their way into the linear accelerator.
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Field Emission In field emission, electrons tunnel through a potential barrier, rather than escaping over it as in thermionic emission or photoemission.Gomer, R., "Field emission," McGraw Hill Access Science Encyclopedia, Vol. 2005, No. July 1, 2002, pp. 2. For a metal at low temperature, the process can be understood in terms of the figure below.
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In 1925 invented a microphone based on thermionic currents (currents emitted by heated bodies) and a light projector using the interference phenomenon. Founded in the same year the first Electricity and Magnetism Laboratory, as well as the first Chair of Electricity and Magnetism in the Department of Mathematics and Physics at the University of Bucharest.
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The Robinson machines were limited in speed and reliability. Tommy Flowers of the Post Office Research Station, Dollis Hill had experience of thermionic valves and built an electronic machine, the Colossus computer which was installed in the Newmanry. This was a great success and ten were in use by the end of the war.
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The EIA type 4307A is a power output pentode possessing a similar power rating, but significantly different characteristics to the far more common type 807 thermionic valve/vacuum tube. The "SY" prefix denotes the site of manufacture as being Sydney. The plant, operated by Standard Telephones and Cables Pty. Ltd. was located on Mandible StreetN.
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With the development of the RF antenna ion source, or "non-thermionic ion source," the ion source has an advantage over conventional cold cathodes and hot filament ion sources. The filament continuously burns out over time with a shorter lifespan, requiring venting of the ion source to atmosphere and rebuilding of the ion source.
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It contained 550 thermionic valves – 300 diodes and 250 pentodes – and had a power consumption of 3.5 kilowatts. Its successful operation was reported in a letter to the journal Nature published in September 1948, establishing it as the world's first stored-program computer. It quickly evolved into a more practical machine, the Manchester Mark 1.
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In November 1904, the English physicist John Ambrose Fleming invented the two-electrode vacuum-tube rectifier, which he called the Fleming oscillation valve.Van der Bijl, Hendrik Johannes (1920) The Thermionic Vacuum Tube and its Applications, pp. 111–112 for which he obtained GB patent 24850 and .Fleming Valve patent "Instrument for converting alternating electric currents into continuous currents".
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Peak kilovoltage (kVp) refers to the maximum high voltage applied across an X-ray tube to produced the xrays.The kvp of x-ray tude qualify the quality of the x-ray.More the kvp used it's enhance the contrast of x-ray image. During x-ray generation, surface electrons are released from a heated cathode by thermionic emission.
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The starting method and frequency affects cathode sputtering. A filament may also break, disabling the lamp. This tube, which was turned on and off regularly, could no longer start after enough thermionic emission mix had sputtered from the cathodes. The vaporized material adheres to the glass surrounding the electrodes, causing it to darken and turn black.
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Electron emission microscopy is a type of electron microscopy in which the information carrying beam of electrons originates from the specimen. The source of energy causing the electron emission can be heat (thermionic emission), light (photoelectron emission), ions, or neutral particles, but normally excludes field emission and other methods involving a point source or tip microscopy.
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A thermionic converter consists of a hot electrode which thermionically emits electrons over a potential energy barrier to a cooler electrode, producing a useful electric power output. Caesium vapor is used to optimize the electrode work functions and provide an ion supply (by surface ionization or electron impact ionization in a plasma) to neutralize the electron space charge.
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Recent studies have shown that excited Cs-atoms in thermionic converters form clusters of Cs-Rydberg matter which yield a decrease of collector emitting work function from 1.5 eV to 1.0 – 0.7 eV. Due to long- lived nature of Rydberg matter this low work function remains low for a long time which essentially increases the low-temperature converter’s efficiency.
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In 1926, Okabe developed a magnetron device that significantly decreased the operating wavelength of oscillations.Okabe, Kinjiro; “On the Applications of Various Electronic Phenomena and the Thermionic Tubes of New Types,”Journal of the IEE of Japan, vol. 473 (Suppl. Issue), 1927, p. 13 He filed for a U.S. patent in 1926, which was granted in 1929 (No. 1,735,294).
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This is a list of vacuum tubes or thermionic valves, and low-pressure gas- filled tubes, or discharge tubes. Before the advent of semiconductor devices, thousands of tube types were used in consumer electronics. Many industrial, military or otherwise professional tubes were also produced. Only a few types are still used today, mainly in high-power, high-frequency applications.
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When the Mark I started running in 1951, reliability was poor. The primary concern was the drum memory system, which broke down all the time. Additionally, the machine used 4,200 thermionic valves, mostly EF50 pentodes and diodes that had to be replaced constantly. The Williams tubes, used as random access memory and registers, were reliable but required constant maintenance.
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This reactor was cooled by liquid sodium-potassium (NaK) metal, and used a high-temperature moderator containing hydrogen and highly enriched fuel. The reactor produced electricity using a thermionic converter. The satellite used a Plazma-2 SPT Hall-effect thruster from propulsion. The mission of Kosmos 1867 was to search the oceans for naval and merchant vessels.
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The Atanasoff–Berry Computer (ABC), ENIAC, and Colossus all used thermionic valves (vacuum tubes). ENIAC's registers performed decimal arithmetic, rather than binary arithmetic like the Z3, the ABC and Colossus. Like the Colossus, ENIAC required rewiring to reprogram until April 1948.See #Improvements In June 1948, the Manchester Baby ran its first program and earned the distinction of first electronic stored-program computer.
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Sometime during his military years, he became a member of the Institution of Electrical Engineers. He became the chief engineer in the Sudanese Department of Posts and Telegraphs department for five years in Sudan before finally returning home to Ireland. He also wrote a paper on thermionic generators around this time. In 1931, he returned to his parents' home Cherbury, in Booterstown.
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Light loss is due to filament evaporation and bulb blackening.IEC 60064 Tungsten filament lamps for domestic and similar general lighting purposes. Study of the problem of bulb blackening led to the discovery of the Edison effect, thermionic emission and invention of the vacuum tube. A very small amount of water vapor inside a light bulb can significantly affect lamp darkening.
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However, when forward-biased, an effect occurs called quantum mechanical tunneling which gives rise to a region in its voltage vs. current behavior where an increase in forward voltage is accompanied by a decrease in forward current. This "negative resistance" region can be exploited in a solid state version of the dynatron oscillator which normally uses a tetrode thermionic valve (vacuum tube).
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Until the invention of the transistor in 1947, most practical high-frequency electronic amplifiers were made using thermionic valves.Solid state devices such as the cat's-whisker detector, copper oxide rectifier, or crystal detector diode were known before the transistor, but were unable to amplify a signal. Magnetic amplifiers were limited to below roughly 200kHz. Hydraulic amplifiers were not directly useful as electronic devices.
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He was best known for his work on thermionic vacuum tubes. In 1911 he invented the concept of the Chaffee Gap which was a way of producing continuous oscillations for long-distance telephone transmissions and in 1924 he started to work on controlling weather, using aircraft to break up clouds with electrically charged grains of sands. Chaffee died in Waltham, Massachusetts.
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A set of cold cathode discharge tubes A cold cathode, Cold cathode discharge tube is a cathode that is not electrically heated by a filament.A negatively charged electrode emits electrons or is the positively charged terminal. For more, see field emission. A cathode may be considered "cold" if it emits more electrons than can be supplied by thermionic emission alone.
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All the applications cited above have employed technology in which the basic physical understanding and performance of the thermionic converter were essentially the same as those achieved before 1970. During the period from 1973 to 1983, however, significant research on advanced low- temperature thermionic converter technology for fossil-fueled industrial and commercial electric power production was conducted in the US, and continued until 1995 for possible space reactor and naval reactor applications. That research has shown that substantial improvements in converter performance can be obtained now at lower operating temperatures by addition of oxygen to the caesium vapor,J-L. Desplat, L.K. Hansen, G.L. Hatch, J.B. McVey and N.S. Rasor, “HET IV Final Report”, Volumes 1 & 2, Rasor Associates Report #NSR-71/95/0842, (Nov. 1995); performed for Westinghouse Bettis Laboratory under Contract # 73-864733; 344 pages.
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Richardson's grave in Brookwood Cemetery Richardson was elected a Fellow of the Royal Society (FRS) in 1913, and was awarded its Hughes Medal in 1920. He was awarded the Nobel Prize in Physics in 1928, "for his work on the thermionic phenomenon and especially for the discovery of the law named after him".Nobel prize citation, Nobel foundation website He was knighted in 1939.
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Trochotrons were used in the UNIVAC 1101 computer, as well as in clocks and frequency counters. The first trochotrons were surrounded by a hollow cylindrical magnet, with poles at the ends. The field inside the magnet had essentially-parallel lines of force, parallel to the axis of the tube. It was a thermionic vacuum tube; inside were a central cathode, ten anodes, and ten "spade" electrodes.
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In 1974 Hess returned to the University of Vienna as assistant professor. In 1977 he was offered a position as a visiting associate professor which enabled him to return to UIUC. Hess worked on improving the efficiency of charge-coupled devices. He and Ben G. Streetman developed the concept of "real space transfer" to describe the performance of high-frequency transistors involving hot‐electron thermionic emission.
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Werner H. Bloss studied Physics at the University of Tübingen and the University of Stuttgart. In 1955 he took the position of a research assistant at the Institute of Gas Discharge Techniques and Photoelectronics at the University of Stuttgart. Here he came into contact with various methods of energy conversion. In his doctoral thesis he described the noble gas filled thermionic converter developed by him.
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Sputtering of the electrode may still occur, but electrodes can be shaped (e.g. into an internal cylinder) to capture most of the sputtered material so it is not lost from the electrode. Cold cathode lamps are generally less efficient than thermionic emission lamps because the cathode fall voltage is much higher. Power dissipated due to cathode fall voltage does not contribute to light output.
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This is a list of European Mullard–Philips vacuum tubes and their American equivalents. Most post-war European thermionic valve (vacuum tube) manufacturers have used the Mullard–Philips tube designation naming scheme. Special quality variants may have the letters "SQ" appended, or the device description letters may be swapped with the numerals (e.g. an E82CC is a special quality version of an ECC82) Note: Typecode explained above.
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Cunife is an alloy of copper (Cu), nickel (Ni), iron (Fe), and in some cases cobalt (Co). The alloy has the same linear coefficient of expansion as certain types of glass, and thus makes an ideal material for the lead out wires in light bulbs and thermionic valves. Fernico exhibits a similar property. It is a magnetic alloy and can be used for making magnets.
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Sound on Sound (October 2004). Retrieved 03–21–2011. Howlett purchased and brought a laptop, a copy of the Reason program and selected a "Thermionic Culture Phoenix valve compressor and Culture Vulture distortion unit, a Korg Micro Keyboard, a Manley Laboratories valve EQ and a 1970s Korg MS20 analogue keyboard". He would write the songs in "his bed", and then create them using those equipment.
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They can be calibrated against a McLeod gauge which is much more stable and independent of gas chemistry. Thermionic emission generates electrons, which collide with gas atoms and generate positive ions. The ions are attracted to a suitably biased electrode known as the collector. The current in the collector is proportional to the rate of ionization, which is a function of the pressure in the system.
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It was one of the main developers of the Topaz-2 satellite nuclear power reactor and is developing thermionic fuel elements and other materials for the Topaz-3 nuclear power reactor. NPO "Luch" has also conducted extensive work on high- temperature cores for nuclear rocket propulsion, designed for space projects. The Associated Expedition of NPO "Luch", the enterprise's field test facility, is located at Semey in Kazakhstan.
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Energy level diagrams for thermionic diode in retarding potential configuration. The barrier is the vacuum near collector surface. The same setup can be used to instead measure the work function in the collector, simply by adjusting the applied voltage. If an electric field is applied away from the emitter instead, then most of the electrons coming from the emitter will simply be reflected back to the emitter.
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20, pp. 76-78. It was able to develop higher voltages from induction coils, and was widely employed in the large induction coils that powered early x-ray machines until the 1920s. Much of Wehnelt's research dealt with thermionic emission, the emission of electrons in vacuum tubes. In this context, he developed in 1902/03 the Wehnelt cylinder, an electrode used in electron guns.
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In 1922 regular wireless broadcasts for entertainment began in the UK from the Marconi Research Centre 2MT at Writtle near Chelmsford, England. Early radios ran the entire power of the transmitter through a carbon microphone. In the 1920s, the Westinghouse company bought Lee de Forest's and Edwin Armstrong's patent. During the mid-1920s, Amplifying vacuum tubes (US)/thermionic valves (UK) revolutionized radio receivers and transmitters.
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Roger Bucknall was born in Selly Oak, Birmingham in 1950, studied at Bounville Boys Technical School. He read for an honours degree in Mechanical Engineering at Nottingham University before working for Racal Thermionic in Hythe, Hampshire, as a technical author, then mechanical designer for industrial tape recorders from 1971-73. Fylde Guitars was formed in 1973. Moved to Fylde, Lancashire and now resides in Penrith, Cumbria.
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A small electrical heater heated the mica, causing it to release a small amount of air, thus restoring the tube's efficiency. However, the mica had a limited life, and the restoration process was difficult to control. In 1904, John Ambrose Fleming invented the thermionic diode, the first kind of vacuum tube. This used a hot cathode that caused an electric current to flow in a vacuum.
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Layout of optical components in a basic TEM Hairpin style tungsten filamentLaB6 filament From the top down, the TEM consists of an emission source or cathode, which may be a tungsten filament or needle, or a lanthanum hexaboride (LaB6) single crystal source. The gun is connected to a high voltage source (typically ~100–300 kV) and, given sufficient current, the gun will begin to emit electrons either by thermionic or field electron emission into the vacuum. In the case of a thermionic source, the electron source is typically mounted in a Wehnelt cylinder to provide preliminary focus of the emitted electrons into a beam while also stabilizing the current using a passive feedback circuit. A field emission source uses instead electrostatic electrodes called an extractor, a suppressor, and a gun lens, with different voltages on each, to control the electric field shape and intensity near the sharp tip.
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Cadmium arsenide is a II-V semiconductor showing degenerate n-type semiconductor intrinsic conductivity with a large mobility, low effective mass and highly non parabolic conduction band, or a Narrow-gap semiconductor. It displays an inverted band structure, and the optical energy gap, eg, is less than 0. When deposited by thermal evaporation (deposition), cadmium arsenide displayed the Schottky (thermionic emission) and Poole–Frenkel effect at high electric fields.
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A cold cathode is a cathode that is not electrically heated by a filament. A cathode may be considered "cold" if it emits more electrons than can be supplied by thermionic emission alone. It is used in gas-discharge lamps, such as neon lamps, discharge tubes, and some types of vacuum tube. The other type of cathode is a hot cathode, which is heated by electric current passing through a filament.
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They had eight Enigma-equivalents on the front and eight on the back. The fast drum rotated at 1,725 rpm, 34 times the speed of the early British bombes. 'Stops' were detected electronically using thermionic valves (vacuum tubes)--mostly thyratrons--for the high-speed circuits. When a 'stop' was found the machine over-ran as it slowed, reversed to the position found and printed it out before restarting.
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In an ideal gas, and in other theoretically understood bodies, the Kelvin temperature is defined to be proportional to the average kinetic energy of non-interactively moving microscopic particles, which can be measured by suitable techniques. The proportionality constant is a simple multiple of the Boltzmann constant. If molecules, atoms, or electrons,Germer, L.H. (1925). 'The distribution of initial velocities among thermionic electrons', Phys. Rev., 25: 795–807.
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High density plasmas can also be generated by a DC discharge in an electron-rich environment, obtained by thermionic emission from heated filaments. The voltages required by the arc discharge are of the order of a few tens of volts, resulting in low energy ions. The high density, low energy plasma is exploited for the epitaxial deposition at high rates in Low-Energy Plasma-Enhanced chemical vapor deposition reactors.
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The operating temperature of the cathode causes it to release electrons into the vacuum, a process called thermionic emission. The cathode is coated with oxides of alkaline earth metals, such as barium and strontium oxides. These have a low work function, meaning that they more readily emit electrons than would the uncoated cathode. The plate, not being heated, does not emit electrons; but is able to absorb them.
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Prof Ivan de Burgh Daly CBE FRS FRSE (14 April 1893 - 8 February 1974) was a British experimental physiologist and animal physiologist. He had a specialist knowledge of ECG use and was awarded a Beit Fellowship in this field in 1920. Together with Shellshear, he was the first in England to use thermionic valves in any biological context. In 1948 he established the foundation of the Babraham Institute.
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The cathode is the negative electrode. Any gas- discharge lamp has a positive (anode) and a negative electrode. Both electrodes alternate between acting as an anode and a cathode when these devices run with alternating current. A standard computer case fitted with blue and green cold-cathode tubes Cold-cathode fluorescent lamp backlight A cold cathode is distinguished from a hot cathode that is heated to induce thermionic emission of electrons.
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Lower-resolution systems can use thermionic sources, which are usually formed from lanthanum hexaboride. However, systems with higher-resolution requirements need to use field electron emission sources, such as heated W/ZrO2 for lower energy spread and enhanced brightness. Thermal field emission sources are preferred over cold emission sources, in spite of the former's slightly larger beam size, because they offer better stability over typical writing times of several hours.
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When hot, the filament releases electrons into the vacuum, a process called thermionic emission, originally known as the Edison effect. A second electrode, the anode or plate, will attract those electrons if it is at a more positive voltage. The result is a net flow of electrons from the filament to plate. However, electrons cannot flow in the reverse direction because the plate is not heated and does not emit electrons.
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De Forest Audion tube from 1908, the first triode. The flat plate is visible at top, with the zigzag wire grid under it. The filament was originally under the grid but has burned out. Lieben-Reisz tube, another primitive triode developed the same time as the Audion by Robert von Lieben Before thermionic valves were invented, Philipp Lenard used the principle of grid control while conducting photoelectric experiments in 1902.
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As the contacts are separated, a few small points of contact become the last to separate. The current becomes constricted to these small hot spots, causing them to become incandescent, so that they emit electrons (through thermionic emission). Even a small 9 V battery can spark noticeably by this mechanism in a darkened room. The ionized air and metal vapour (from the contacts) form plasma, which temporarily bridges the widening gap.
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The Soviets had much larger rockets and could use vacuum tubes (thermionic valves) in their guidance systems. (The weights of the Minuteman I and II remain classified, but the Minuteman III was 35,000 kg versus the Soviet R-7 missile (1959) of 280,000 kg.) The US planners had to choose either to develop solid state guidance systems (which weigh less) or consider the additional cost and time delay of developing larger rockets.
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Elster and Geitel, who also worked on thermionic emission, proposed a theory to explain thunderstorms' electrical structure (1885) and, later, discovered atmospheric radioactivity (1899) from the existence of positive and negative ions in the atmosphere. Pockels (1897) estimated lightning current intensity by analyzing lightning flashes in basalt (c. 1900)Vladimir A. Rakov, Martin A. Uman (2003) Lightning: Physics and Effects. Cambridge University Press and studying the left-over magnetic fields caused by lightning.
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They are also used in microwave linear beam vacuum tubes such as klystrons, inductive output tubes, travelling wave tubes, and gyrotrons, as well as in scientific instruments such as electron microscopes and particle accelerators. Electron guns may be classified by the type of electric field generation (DC or RF), by emission mechanism (thermionic, photocathode, cold emission, plasmas source), by focusing (pure electrostatic or with magnetic fields), or by the number of electrodes.
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Tungar bulbs from 1917, 2 ampere (left) and 6 ampere The General Electric Tungar rectifier was a mercury vapor (ex.:5B24) or argon (ex.:328) gas-filled electron tube device with a tungsten filament cathode and a carbon button anode. It operated similarly to the thermionic vacuum tube diode, but the gas in the tube ionized during forward conduction, giving it a much lower forward voltage drop so it could rectify lower voltages.
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Caesium vapour thermionic generators are low-power devices that convert heat energy to electrical energy. In the two-electrode vacuum tube converter, caesium neutralizes the space charge near the cathode and enhances the current flow. Caesium is also important for its photoemissive properties, converting light to electron flow. It is used in photoelectric cells because caesium-based cathodes, such as the intermetallic compound , have a low threshold voltage for emission of electrons.
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The photocathodes can be made of a variety of materials, with different properties. Typically the materials have low work function and are therefore prone to thermionic emission, causing noise and dark current, especially the materials sensitive in infrared; cooling the photocathode lowers this thermal noise. The most common photocathode materials arePhotomultiplier Tubes. Construction and Operating Characteristics. Connections to External Circuits, Hamamatsu Ag-O-Cs (also called S1) transmission-mode, sensitive from 300–1200 nm.
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Some important parameters include plasma density, electron and ion temperature, ion molecular weight, magnetic field strength and orbital velocity relative to the surrounding plasma. Then there is active collection and emission techniques involved in an EDT system. This occurs through devices such as a hollow cathode plasma contactors, thermionic cathodes, and field emitter arrays. The physical design of each of these structures as well as the current emission capabilities are thoroughly discussed.
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In 1998, Chapman was Chief Scientist of Rotary Rocket of San Mateo, California. Rotary Rocket built and flew atmospheric tests of the Roton, a novel manned, re-usable space launch vehicle. In 2004, Chapman presented two papers at the 55th International Astronautical Congress (Vancouver CANADA). The first, "Luces in the Sky with Diamonds," presented a design for a gossamer, iso-inertial SPS using thin films of artificial diamond in thermionic conversion devices.
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Vacuum tubes (Thermionic valves) were among the earliest electronic components. They were almost solely responsible for the electronics revolution of the first half of the twentieth century. They allowed for vastly more complicated systems and gave us radio, television, phonographs, radar, long-distance telephony and much more. They played a leading role in the field of microwave and high power transmission as well as television receivers until the middle of the 1980s.
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Electrons are emitted by the hot plate through thermionic emission, and ions are created through contact ionization of atoms of alkali metals that have low ionisation potentials. The hot plate is made of a metal that has a large work function and can withstand high temperatures, e.g. tungsten or rhenium. The alkali metal is boiled in an oven that is designed to direct a beam of alkaline metal vapour onto the hot plate.
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Radio- & TV repair-man's tool for testing microphony in thermionic valves (tubes). The black rubber grommet gives the valve (tube) a firm but safe impact. A special tool, called a valve hammer, or tube hammer was sometimes used to safely tap the device suspected of being microphonic, while it was operating, so checking if such a tap would produce objectional audio effects. Microwave tube designers took numerous steps to reduce microphonics in klystrons.
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Electrons released by the filament were attracted to the plate when it had a positive voltage. Thermionic emission is the liberation of electrons from an electrode by virtue of its temperature (releasing of energy supplied by heat). This occurs because the thermal energy given to the charge carrier overcomes the work function of the material. The charge carriers can be electrons or ions, and in older literature are sometimes referred to as thermions.
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The need for rapid easily automated systems led to massive advances in the understanding and use of the induction hardening process and by the late 1950s many systems using motor generators and thermionic emission triode oscillators were in regular use in a vast array of industries. Modern day induction heating units use the latest in semiconductor technology and digital control systems to develop a range of powers from 1 kW to many megawatts.
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In the triode, electrons are released into the tube from the metal cathode by heating it, a process called thermionic emission. The cathode is heated red hot by a separate current flowing through a thin metal filament. In high power triodes, the filament itself is the cathode, while in most the filament heats a separate cathode electrode. Virtually all the air is removed from the tube, so the electrons can move freely.
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Semiconductor devices have replaced thermionic devices (vacuum tubes) in most applications. Semiconductor devices are manufactured both as single discrete devices and as integrated circuits (ICs), which consist of a number—from a few to millions—of devices manufactured and interconnected on a single semiconductor substrate. Of all the semiconductors in use today, silicon makes up the largest portion both by quantity and commercial value. Monocrystalline silicon is used to produce wafers used in the semiconductor and electronics industry.
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This is equivalent to peak detection with a suitably long time constant. The amplitude of the recovered audio frequency varies with the modulating audio signal, so it can drive an earphone or an audio amplifier. Fessendon invented the first AM demodulator in 1904 called the electrolytic detector, consisting of a short needle dipping into a cup of dilute acid. The same year John Ambrose Fleming invented the Fleming valve or thermionic diode which could also rectify an AM signal.
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Secondary emission can be undesirable such as in the tetrode thermionic valve (tube). In this instance the positively charged screen grid can accelerate the electron stream sufficiently to cause secondary emission at the anode (plate). This can give rise to excessive screen grid current. It is also partly responsible for this type of valve (tube), particularly early types with anodes not treated to reduce secondary emission, exhibiting a 'negative resistance' characteristic, which could cause the tube to become unstable.
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However, this is less significant with longer tubes. The increased power dissipation at tube ends also usually means cold cathode tubes have to be run at a lower loading than their thermionic emission equivalents. Given the higher tube voltage required anyway, these tubes can easily be made long, and even run as series strings. They are better suited for bending into special shapes for lettering and signage, and can also be instantly switched on or off.
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This is a cathode that is not heated by a filament. They may emit electrons by field electron emission, and in gas- filled tubes by secondary emission. Some examples are electrodes in neon lights, cold-cathode fluorescent lamps (CCFLs) used as backlights in laptops, thyratron tubes, and Crookes tubes. They do not necessarily operate at room temperature; in some devices the cathode is heated by the electron current flowing through it to a temperature at which thermionic emission occurs.
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EuB6 is a semiconductor and the rest are good conductors. LaB6 and CeB6 are thermionic emitters, used, for example, in scanning electron microscopes. Dodecaborides, LnB12, are formed by the heavier smaller lanthanides, but not by the lighter larger metals, La – Eu. With the exception YbB12 (where Yb takes an intermediate valence and is a Kondo insulator), the dodecaborides are all metallic compounds. They all have the UB12 structure containing a 3 dimensional framework of cubooctahedral B12 clusters.
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Fleming was bitter about his treatment. He honoured his agreement and didn't speak about it throughout Marconi's life, but after his death in 1937 said Marconi had been "very ungenerous". In 1904, working for the Marconi company to improve transatlantic radio reception, Fleming invented the first thermionic vacuum tube, the two-electrode diode, which he called the oscillation valve, for which he received a patent on 16 November.Fleming Valve patent It became known as the Fleming valve.
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He was able to establish a theoretical correlation between the Volta Effect and the Peltier Effect. In 1928 he discovered that Enrico Fermi's theory on free electrons could be used to predict the constants of the photoelectric effect and thermionic effect in Volta's and Peltier's equations. In 1930 Perucca turned his attention to the photoelectric effect. He developed a new type of electric-current/voltage measuring device called the Elettrometro di Perucca which was highly sensitive.
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SP-100 nuclear power system SP-100 (Space reactor PrototypeAcronyms: SP-100 means Space reactor prototype) was a U.S. research program for nuclear fission reactors usable as small fission power systems for spacecraft. It was started in 1983 by NASA, the US Department of Energy and other agencies.SP-100, the US Space Nuclear Reactor Power Program, Technical information report. Available at Energy Citations Database A reactor was developed with heat pipes transporting the heat to thermionic converters.
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A tetrode is a vacuum tube (called valve in British English) having four active electrodes. The four electrodes in order from the centre are: a thermionic cathode, first and second grids and a plate (called anode in British English). There are several varieties of tetrodes, the most common being the screen-grid tube and the beam tetrode. In screen-grid tubes and beam tetrodes, the first grid is the control grid and the second grid is the screen grid.
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Moreover, the minimum energy can be misleading in materials where there are no actual electron states at the Fermi level that are available for excitation. For example, in a semiconductor the minimum photon energy would actually correspond to the valence band edge rather than work function. Of course, the photoelectric effect may be used in the retarding mode, as with the thermionic apparatus described above. In the retarding case, the dark collector's work function is measured instead.
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Applying the field causes lowering of the barrier, and thus enhances the emission current in thermionic emission. This is called the "Schottky effect", and the resulting emission regime is called "Schottky emission". In 1923 Schottky suggested (incorrectly) that the experimental phenomenon then called autoelectronic emission and now called field electron emission resulted when the barrier was pulled down to zero. In fact, the effect is due to wave-mechanical tunneling, as shown by Fowler and Nordheim in 1928.
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The DEUCE had 1450 thermionic valves, and used mercury delay lines for its main memory; each of the 12 delay lines could store 32 instructions or data words of 32 bits each. It adopted the then high 1 megahertz clock rate of the Pilot ACE. Input/output was via Hollerith 80-column punch-card equipment. The reader read cards at the rate of 200 per minute, while the card punch rate was 100 cards per minute.
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This changed for iii as the singer put his focus on his studio efforts rather than his stage performance. He adapted his singing style based on the needs of each song throughout the album, using a "sneering tone" on "Genghis Khan". The track was mixed by the band and Niklas Flyckt. Flyckt utilized a Urei 1176LN limiting amplifier to emphasize the ghost notes, and a Thermionic Culture Vulture to enhance the sound without causing digital domain issues.
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In 1873, Frederick Guthrie observed that a grounded, white-hot metal ball brought in close proximity to an electroscope would discharge a positively charged electroscope, but not a negatively charged electroscope.Guthrie, Frederick (October 1873) "On a relation between heat and static electricity," The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 4th series, 46: 257–266.1928 Nobel Lecture: Owen W. Richardson, "Thermionic phenomena and the laws which govern them", December 12, 1929, In 1880, Thomas Edison observed unidirectional current between heated and unheated elements in a bulb, later called Edison effect, and was granted a patent on application of the phenomenon for use in a DC voltmeter.Edison, Thomas A. "Electrical Meter" Issue date: Oct 21, 1884 About 20 years later, John Ambrose Fleming (scientific adviser to the Marconi Company and former Edison employee) realized that the Edison effect could be used as a radio detector. Fleming patented the first true thermionic diode, the Fleming valve, in Britain on November 16, 1904 (followed by in November 1905).
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A field emission gun (FEG) is a type of electron gun in which a sharply pointed Müller-type emitter is held at several kilovolts negative potential relative to a nearby electrode, so that there is sufficient potential gradient at the emitter surface to cause field electron emission. Emitters are either of cold-cathode type, usually made of single crystal tungsten sharpened to a tip radius of about 100 nm, or of the Schottky type, in which thermionic emission is enhanced by barrier lowering in the presence of a high electric field. Schottky emitters are made by coating a tungsten tip with a layer of zirconium oxide (ZrO) decreasing the work function of the tip by approximately 2.7 eV. In electron microscopes, a field emission gun is used to produce an electron beam that is smaller in diameter, more coherent and with up to three orders of magnitude greater current density or brightness than can be achieved with conventional thermionic emitters such as tungsten or lanthanum hexaboride ()-tipped filaments.
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Relays and vacuum tubes (thermionic tubes) were commonly used as switching elements; a useful computer requires thousands or tens of thousands of switching devices. The overall speed of a system is dependent on the speed of the switches. Tube computers like EDVAC tended to average eight hours between failures, whereas relay computers like the (slower, but earlier) Harvard Mark I failed very rarely. In the end, tube- based CPUs became dominant because the significant speed advantages afforded generally outweighed the reliability problems.
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Ferris, Clifford "Electron tube fundamentals" in The cathode is heated to a temperature that causes electrons to be 'boiled off' of its surface into the evacuated space in the tube, a process called thermionic emission. There are two types of hot cathodes: ;Directly heated cathode: In this type, the filament itself is the cathode and emits the electrons directly. Directly heated cathodes were used in the first vacuum tubes. Today, they are used in fluorescent tubes and most high-power transmitting vacuum tubes.
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The Electron beam ion trap (EBIT), based on the same principle, can produce up to bare uranium ions and can be used as an ion source as well. Heavy ions can also be generated with an Ion Gun which typically uses the thermionic emission of electrons to ionize a substance in its gaseous state. Such instruments are typically used for surface analysis.Ion beam deposition system with mass separator Gas flows through the ion source between the anode and the cathode.
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Stanley Walter Croucher Pack (1904–1977) (CBE) was an officer in the Royal Navy, and an author of several books related to maritime topics. In 1928, while an instructor Commander at Dartmouth Naval College, he wrote a meteorology textbook entitled The Frequency Departure of Thermionic Oscillators from the L. C. Valve. Decades later he wrote a book about the college, entitled Britannia at Dartmouth. In 1953 the London Gazette reported he had been promoted from Instructor Commander to Instructor Captain.
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The design of the distributed amplifiers was first formulated by William S. Percival in 1936.W. S. Percival, “Thermionic Valve Circuits,” British Patent Specification no. 460,562, filed 24 July 1936, granted January 1937. In that year Percival proposed a design by which the transconductances of individual vacuum tubes could be added linearly without lumping their element capacitances at the input and output, thus arriving at a circuit that achieved a gain-bandwidth product greater than that of an individual tube.
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Lamps are divided into families based on the pressure of gas, and whether or not the cathode is heated. Hot cathode lamps have electrodes that operate at a high temperature and are heated by the arc current in the lamp. The heat knocks electrons out of the electrodes by thermionic emission, which helps maintain the arc. In many types the electrodes consist of electrical filaments made of fine wire, which are heated by a separate current at startup, to get the arc started.
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Some of their subsequent experiments on thermionic emission provided experimental validation for the Sommerfeld theory. They also did work on the surface state and work function of tungsten and the adsorption of thorium atoms. Through his studies of rectification and photo-effects on the semiconductor surfaces of cuprous oxide and silicon, Brattain discovered the photo-effect at the free surface of a semiconductor. This work was considered by the Nobel prize committee to be one of his chief contributions to solid state physics.
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A "Sylvania Electric" multimeter tester for vacuum tubes A tube tester is an electronic instrument designed to test certain characteristics of vacuum tubes (thermionic valves). Tube testers evolved along with the vacuum tube to satisfy the demands of the time, and their evolution ended with the tube era. The first tube testers were simple units designed for specific tubes to be used in the battlefields of World War I by radio operators, so they could easily test the tubes of their communication equipment.
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A transistor is a semiconductor device with at least three terminals for connection to an electric circuit. In the common case, the third terminal controls the flow of current between the other two terminals. This can be used for amplification, as in the case of a radio receiver, or for rapid switching, as in the case of digital circuits. The transistor replaced the vacuum-tube triode, also called a (thermionic) valve, which was larger and used significantly more power to operate.
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A binary clock, hand-wired on breadboards A digital circuit is typically constructed from small electronic circuits called logic gates that can be used to create combinational logic. Each logic gate is designed to perform a function of boolean logic when acting on logic signals. A logic gate is generally created from one or more electrically controlled switches, usually transistors but thermionic valves have seen historic use. The output of a logic gate can, in turn, control or feed into more logic gates.
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The first recorded time of isolating a single action potential was carried out by Edgar Adrian in 1925 from a set of crosscut muscle fibres. Using a thermionic triode valve amplifier with 1850 amplification, Adrian noticed that when the muscle preparation was left to hang, it produced oscillations; yet when supported, no such activity occurred. Later with the help of Yngve Zotterman, Adrian isolated and stimulated one sensory fibre. The impulses externally on the fibre were uniform: “as simple as the dots in Morse code”.
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Introduction to Metal Oxide Varistors, www.powerguru.org When a small voltage is applied across the electrodes, only a tiny current flows, caused by reverse leakage through the diode junctions. When a large voltage is applied, the diode junction breaks down due to a combination of thermionic emission and electron tunneling, resulting in a large current flow. The result of this behavior is a nonlinear current-voltage characteristic, in which the MOV has a high resistance at low voltages and a low resistance at high voltages.
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In the early sixties, very successful research work on various types of thermionic converters was performed under his guidance at the above-mentioned institute. In the autumn of 1967 he took a position as Associate Professor at the University of Florida in Gainesville, Florida. During his two-year stay in the United States his field of interest widened again to take in optical methods of image processing. After returning from the US he implemented this novel field of research at the institute in Stuttgart.
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These form a metal layer on the surface which emits more electrons. Treated cathodes require less surface area, lower temperatures and less power to supply the same cathode current. The untreated thoriated tungsten filaments used in early vacuum tubes (called "bright emitters") had to be heated to 2500 °F (1400 °C), white-hot, to produce sufficient thermionic emission for use, while modern coated cathodes produce far more electrons at a given temperature, so they only have to be heated to 800–1100 °F (425–600 °C).
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The 955 is an indirectly heated triode with heater electrically isolated from the cathode. The heater has a 6.3 volt rating, which it shares with many other common thermionic valves/electron tubes, and it draws about 150 mA. The maximum anode voltage is 250 V, with an anode current of 420 microamperes and anode load 250 kilohm, and the maximum anode current is 4.5 mA at a voltage of 180 V with an anode load of 20 kilohm.Philips Valve Data Book, Philips Electrical Industries Pty. Ltd.
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Photo taken through an end port with the plasma off, showing the thermionic cathode. The LAPD is a linear pulsed-discharge device operated at a high (1 Hz) repetition rate, producing a strongly magnetized background plasma which is physically large enough to support Alfvén waves. Plasma is produced from a barium oxide (BaO) cathode- anode discharge at one end of a 20-meter long, 1 meter diameter cylindrical vacuum vessel (diagram). The resulting plasma column is roughly 16.5 meters long and 60 cm in diameter.
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19, No. 4, 2003, pp. 595–600. Electrons are emitted from the barium oxide impregnated insert by thermionic emission. A noble gas flows into the insert region of the HC and is partially ionized by the emitted electrons that are accelerated by an electric field near the orifice (Xenon is a common gas used for HCs as it has a low specific ionization energy (ionization potential per unit mass). For EDT purposes, a lower mass would be more beneficial because the total system mass would be less.
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Magnus was born and raised in Belleville, Illinois. She earned degrees in physics and electrical engineering from the University of Missouri–Rolla (now known as the Missouri University of Science and Technology) before earning a PhD in materials science and engineering from the Georgia Institute of Technology in 1996. Research for her dissertation, entitled "An Investigation of the relationship between the thermochemistry and emission behavior of thermionic cathodes based on the BaO-Sc2O3-WO3 ternary system," was supported by a fellowship from the NASA Lewis Research Center.
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4-1000A 1 KW power tetrode in an amateur radio transmitter The tetrode functions in a similar way to the triode, from which it was developed. A current through the heater or filament heats the cathode, which causes it to emit electrons by thermionic emission. A positive voltage is applied between the plate and cathode, causing a flow of electrons from the cathode to plate through the two grids. A varying voltage applied to the control grid can control this current, causing variations in the plate current.
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Typically however the Fermi level is two to five electron volts below the vacuum electrostatic potential energy, depending on the work function of the nearby vacuum wall material. Only at high temperatures will the equilibrium vacuum be populated with a significant number of electrons (this is the basis of thermionic emission). The problem is that not all points in the vacuum are equivalent. At thermodynamic equilibrium, it is typical for electrical potential differences of order 1 V to exist in the vacuum (Volta potentials).
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The plasma source is the most critical component of a LEPECVD reactor, as the low energy, high density, plasma is the key difference from a typical PECVD deposition system. The plasma is generated in a source which is attached to the bottom of the chamber. Argon is fed directly in the source, where tantalum filaments are heated to create an electron-rich environment by thermionic emission. The plasma is then ignited by a DC discharge from the heated filaments to the grounded walls of the source.
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Non-thermionic types, such as a vacuum phototube however, achieve electron emission through the photoelectric effect, and are used for such purposes as the detection of light intensities. In both types, the electrons are accelerated from the cathode to the anode by the electric field in the tube. The simplest vacuum tube, the diode, invented in 1904 by John Ambrose Fleming, contains only a heated electron-emitting cathode and an anode. Electrons can only flow in one direction through the device—from the cathode to the anode.
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Most modern tubes are "indirectly heated" by a "heater" element inside a metal tube that is the cathode. The heater is electrically isolated from the surrounding cathode and simply serves to heat the cathode sufficiently for thermionic emission of electrons. The electrical isolation allows all the tubes' heaters to be supplied from a common circuit (which can be AC without inducing hum) while allowing the cathodes in different tubes to operate at different voltages. H. J. Round invented the indirectly heated tube around 1913.
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Bell's first military contract followed in 1937 with the development of the ill-fated YFM-1 Airacuda, an unconventional bomber-destroyer powered by two Allison-powered pusher propellers. The YFM-1 incorporated groundbreaking technology for the time, with gyro stabilized weapons sighting and a thermionic fire control system. Including the prototype, just 13 Airacudas were produced, and these saw only limited service with the USAAC before being scrapped in 1942. Bell Aircraft Corporation's main factory in Wheatfield, NY (Buffalo / Niagara Falls) during the 1940s.
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This is known as thermionic emission. The electrons are then compressed or focused by the focusing cup into a cloud known as a space charge. High voltage electricity is then applied to the anode on the opposite side of the tube, creating the positive energy needed to attract the negative electron cloud and send the electrons hurtling across the tube with kinetic energy. The electrons then strike the anode target, forcing the electrons to rapidly decelerate and interact with the electrons of the anode target.
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The capabilities and economy of power electronics system are determined by the active devices that are available. Their characteristics and limitations are a key element in the design of power electronics systems. Formerly, the mercury arc valve, the high-vacuum and gas-filled diode thermionic rectifiers, and triggered devices such as the thyratron and ignitron were widely used in power electronics. As the ratings of solid-state devices improved in both voltage and current-handling capacity, vacuum devices have been nearly entirely replaced by solid-state devices.
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Valve electrometers use a specialized vacuum tube (thermionic valve) with a very high gain (transconductance) and input resistance. The input current is allowed to flow into the high impedance grid, and the voltage so generated is vastly amplified in the anode (plate) circuit. Valves designed for electrometer use have leakage currents as low as a few femtoamperes (10−15 amperes). Such valves must be handled with gloved hands as the salts left on the glass envelope can provide leakage paths for these tiny currents.
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Curiosity driven by radioisotope thermoelectric generators In principle, it is possible to build a vehicle powered by nuclear fission or nuclear decay. However there are two major problems: first one has to transform the energy, which comes as heat and radiation into energy usable for a drive. One possible would be to use a steam turbine as in a nuclear power plant, but such a device would take too much space. A more suitable way would be direct conversion into electricity for example with thermoelements or thermionic devices.
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Basic FM quadrature detector circuit using a nonode Nonode 6Л1П (6L1P), Manufactured in Novosibirsk, 1970 A nonode is a type of thermionic valve that has nine active electrodes. The term most commonly applies to a seven-grid vacuum tube, also sometimes called an enneode. An example was the EQ80/UQ80, which was used as an FM quadrature detector. It was developed during the introduction of TV and FM radio and delivered an output voltage large enough to directly drive an end pentode while still allowing for some negative feedback.
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Before the development of silicon semiconductor rectifiers, vacuum tube thermionic diodes and copper oxide- or selenium-based metal rectifier stacks were used. With the introduction of semiconductor electronics, vacuum tube rectifiers became obsolete, except for some enthusiasts of vacuum tube audio equipment. For power rectification from very low to very high current, semiconductor diodes of various types (junction diodes, Schottky diodes, etc.) are widely used. Other devices that have control electrodes as well as acting as unidirectional current valves are used where more than simple rectification is required—e.g.
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The Braun tube was known in 1897, and in 1899 Jonathan Zenneck equipped it with beam-forming plates and a magnetic field for sweeping the trace. Early cathode ray tubes had been applied experimentally to laboratory measurements as early as the 1920s, but suffered from poor stability of the vacuum and the cathode emitters. V. K. Zworykin described a permanently sealed, high-vacuum cathode ray tube with a thermionic emitter in 1931. This stable and reproducible component allowed General Radio to manufacture an oscilloscope that was usable outside a laboratory setting.
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Grover and his colleagues were working on cooling systems for nuclear power cells for space craft, where extreme thermal conditions are encountered. These alkali metal heat pipes transferred heat from the heat source to a thermionic or thermoelectric converter to generate electricity. Since the early 1990s, numerous nuclear reactor power systems have been proposed using heat pipes for transporting heat between the reactor core and the power conversion system. The first nuclear reactor to produce electricity using heat pipes was first operated on September 13, 2012 in a demonstration using flattop fission.
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Although the modelling of electric fields is itself directly useful in some fields such as thermionic valve design, the main practical use of the broader technique is for modelling fields of other quantities. This technique may be applied to any field that follows the same linear rules as Ohm's law for bulk resistivity. This includes heat flow, some optics and some aspects of Newtonian mechanics. It is not usually applicable to fluid dynamics, owing to viscosity and compressibility effects, or to high-intensity optics where non-linear effects become apparent.
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Round made important contributions to development of the first vacuum tubes. He headed Marconi's research program into thermionic tubes, and developed a three-element (triode) amplifying tube at roughly the same time as Lee De Forest was developing the Audion in the US. He discovered feedback (regeneration) in vacuum tubes independently along with Alexander Meissner and Edwin Armstrong, and built some of the first AM vacuum tube radio transmitters. He patented the first design for an indirectly heated cathode, the type of cathode widely used in vacuum tubes today.
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There is growing demand for cesium and its compounds for energy conversion devices such as magneto-hydrodynamic generators, thermionic emitters, and fuel cells. Relatively effective polymer solar cells are built by thermal annealing of cesium carbonate. Cesium carbonate increases the energy effectiveness of the power conversion of solar cells and enhances the life times of the equipment. The studies done on UPS and XPS reveal that the system will do less work due to the thermal annealing of the Cs2CO3 layer. Cesium carbonate breaks down into Cs2O and Cs2O2 by thermal evaporation.
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The type 955 triode "acorn tube" is a small triode thermionic valve (vacuum tube in USA) designed primarily to operate at high frequency. Although data books specify an upper limit of 400–600 MHz, some circuits may obtain gain up to about 900 MHz. Interelectrode capacitances and Miller capacitances are minimized by the small dimensions of the device and the widely separated pins. The connecting pins are placed around the periphery of the bulb and project radially outward: this maintains short internal leads with low inductance, an important property allowing operation at high frequency.
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The work function is determined primarily by a layer of caesium atoms adsorbed on the electrode surfaces. The properties of the interelectrode plasma are determined by the mode of operation of the thermionic converter. In the ignited (or “arc”) mode the plasma is maintained via ionization internally by hot plasma electrons (~ 3300 K); in the unignited mode the plasma is maintained via injection of externally produced positive ions into a cold plasma; in the hybrid mode the plasma is maintained by ions from a hot-plasma interelectrode region transferred into a cold-plasma interelectrode region.
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Also, low on-currents due to the intrinsic resistance of the Schottky contacts are typical of this kind of device just like a very hard and unreliable scalability due to the difficult control of the junction area. Band diagrams of the SBFET operations. From top to bottom: negative applied voltage bend the band diagram enabling a hole tunneling current (p-type); without any voltage applied only thermionic emission is allowed for carriers (off-state); a positive gate voltage enables electrons to tunnel due to the downwards band bending (n-type). Schottky transistor effective circuit.
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The radioactive foil emits a beta particle (electron) which collides with and ionizes the carrier gas to generate more ions resulting in a current. When analyte molecules with electronegative / withdrawing elements or functional groups electrons are captured which results in a decrease in current generating a detector response. Nitrogen–phosphorus detector (NPD), a form of thermionic detector where nitrogen and phosphorus alter the work function on a specially coated bead and a resulting current is measured. Dry electrolytic conductivity detector (DELCD) uses an air phase and high temperature (v.
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Gray also built a simple loudspeaker device into later models, which consisted of a diaphragm vibrating in a magnetic field. A significant invention, which later had a profound effect on electronic music, was the audion in 1906. This was the first thermionic valve, or vacuum tube and which led to the generation and amplification of electrical signals, radio broadcasting, and electronic computation, among other things. Other early synthesizers included the Telharmonium (1897), the Theremin (1919), Jörg Mager's Spharophon (1924) and Partiturophone, Taubmann's similar Electronde (1933), Maurice Martenot's ondes Martenot ("Martenot waves", 1928), Trautwein's Trautonium (1930).
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The EL34 is a thermionic valve or vacuum tube of the power pentode type, first made in 1949. It has an international octal base (indicated by the '3' in the part number) and is found mainly in the final output stages of audio amplification circuits; it was also designed to be suitable as a series regulator by virtue of its high permissible voltage between heater and cathode and other parameters. The American RETMA tube designation number for this tube is 6CA7. The USSR analog was 6P27S (Cyrillic: 6П27C).
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Klystrons amplify RF signals by converting the kinetic energy in a DC electron beam into radio frequency power. In a vacuum, a beam of electrons is emitted by an electron gun or thermionic cathode (a heated pellet of low work function material), and accelerated by high-voltage electrodes (typically in the tens of kilovolts). This beam passes through an input cavity resonator. RF energy has been fed into the input cavity at, or near, its resonant frequency, creating standing waves, which produce an oscillating voltage, which acts on the electron beam.
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After receiving his M.A. in 1905, he began research on thermionic emission in the Cavendish Laboratory. This did not go well, and meanwhile he spent time teaching mathematics to first year engineering students. This hiatus was brief. Through a recommendation by E. T. Whittaker, his senior colleague at Trinity College, he secured a position at the Royal Observatory in Greenwich where he was to embark on his career in astronomy, a career whose seeds had been sown even as a young child when he would often "try to count the stars".
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Photoelectric diode in forward bias configuration, used for measuring the work function We of the illuminated emitter. The photoelectric work function is the minimum photon energy required to liberate an electron from a substance, in the photoelectric effect. If the photon's energy is greater than the substance's work function, photoelectric emission occurs and the electron is liberated from the surface. Similar to the thermionic case described above, the liberated electrons can be extracted into a collector and produce a detectable current, if an electric field is applied into the surface of the emitter.
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The Buchla Music Easel included a number of fader-style controls, switches, patch cord-connected modules, and a keyboard. An analog (or analogue) synthesizer is a synthesizer that uses analog circuits and analog signals to generate sound electronically. The earliest analog synthesizers in the 1920s and 1930s, such as the Trautonium, were built with a variety of vacuum-tube (thermionic valve) and electro-mechanical technologies. After the 1960s, analog synthesizers were built using operational amplifier (op-amp) integrated circuits, and used potentiometers (pots, or variable resistors) to adjust the sound parameters.
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The first commercial AM Audion vacuum tube radio transmitter, built in 1914 by Lee De Forest who invented the Audion (triode) in 1906 During the mid-1920s, amplifying vacuum tubes (or thermionic valves in the UK) revolutionized radio receivers and transmitters. John Ambrose Fleming developed a vacuum tube diode. Lee de Forest placed a screen, added a "grid" electrode, creating the triode. The Dutch company Nederlandsche Radio-Industrie and its owner engineer, Hanso Idzerda, made the first regular wireless broadcast for entertainment from its workshop in The Hague on 6 November 1919.
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A TRF receiver using a grid leak detector (V1) Early applications of triode tubes (Audions) as detectors usually did not include a resistor in the grid circuit.CDR S. S. Robison, Manual of Wireless Telegraphy for the use of Naval Electricians, Annapolis, MD: United States Naval Institute, 1911, pp.125, 132J. Scott-Taggart, Thermionic Tubes in Radio Telegraphy and Telephony, London, UK: The Wireless Press LTD, 1921, p. 118 First use of a resistance to discharge the grid condenser in a vacuum tube detector circuit may have been by Sewall Cabot in 1906.
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X-ray tubes used for continuous-duty operation in fluoroscopy and CT imaging equipment may use a focused cathode and a rotating anode to dissipate the large amounts of heat thereby generated. These are housed in an oil-filled aluminum housing to provide cooling. The photomultiplier tube is an extremely sensitive detector of light, which uses the photoelectric effect and secondary emission, rather than thermionic emission, to generate and amplify electrical signals. Nuclear medicine imaging equipment and liquid scintillation counters use photomultiplier tube arrays to detect low-intensity scintillation due to ionizing radiation.
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A photoinjector is a type of source for intense electron beams which relies on the photoeffect. A laser pulse incident onto the cathode of a photoinjector drives electrons out of it, and into the accelerating field of the electron gun. In comparison with the widespread thermionic electron gun, photoinjectors produce electron beams of higher brightness, which means more particles packed into smaller volume of phase space (beam emittance). Photoinjectors serve as the main electron source for single-pass synchrotron light sources, such as free-electron lasers and for ultrafast electron diffraction setups.
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Here, e is the elementary positive charge, ε0 is the electric constant and εr is the relative permittivity of the second medium (=1 for vacuum). In the case of a metal–semiconductor junction, this is called a Schottky barrier; in the case of the metal-vacuum interface, this is sometimes called a Schottky–Nordheim barrier. In many contexts, h has to be taken equal to the local work function φ. This Schottky–Nordheim barrier (SN barrier) has played an important role in the theories of thermionic emission and of field electron emission.
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He was awarded the Royal Society's Hughes medal in 1936 for his discovery of the Schrot effect (spontaneous current variations in high-vacuum discharge tubes, called by him the "Schrot effect": literally, the "small shot effect") in thermionic emission and his invention of the screen-grid tetrode and a superheterodyne method of receiving wireless signals. In 1964 he received the Werner von Siemens Ring honoring his ground-breaking work on the physical understanding of many phenomena that led to many important technical appliances, among them tube amplifiers and semiconductors.
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It became the Ambrose Fleming technical grammar school for boys. Dr Ambrose Fleming, after whom the school was named, carried out research at the Ponders End Edison Swan factory which led to the diode lamp and the invention of the thermionic valve, a vital early component of radio and television.London’s Lea Valley, Jim Lewis The main bias of the school was Applied Science and Technology, as well as general education, and it took boys from 11 to 18, leading to examinations in GCE O and A levels and Royal Society of Arts qualifications.
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Another experimental setup showing the electron beam orbit When the heater is energized, the heating coil will cause electrons to emerge from it due to thermionic emission. In the electric field between anode and cathode, the electric field acts on the electrons, which accelerate to a high velocity, such that the electrons leave through a small opening in the anode as an electron beam. Only when the coil current is turned on will a force act on the beam and change its direction. Otherwise it will retain its velocity.
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These were important developments in the history of the incandescent light bulb. His work in surface chemistry began at this point, when he discovered that molecular hydrogen introduced into a tungsten-filament bulb dissociated into atomic hydrogen and formed a layer one atom thick on the surface of the bulb. His assistant in vacuum tube research was his cousin William Comings White. As he continued to study filaments in vacuum and different gas environments, he began to study the emission of charged particles from hot filaments (thermionic emission).
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His research, assisted by H.D. Arnold, led to the installation of the first Audion as a repeater on the New York to San Francisco telephone line. In 1915 he co-developed the master oscillator circuit that was used with the Audion for wireless communication between New York and Wilmington, Delaware; and between Paris, France and Honolulu, Hawaii. Van der Bijl published the design and theory of the devices he worked on in a book, The Thermionic Vacuum Tube-Physics and Electronics in 1920. It became the standard textbook on the subject for more than 20 years.
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A great deal of modern solid state physics as produced today stems from this original and early paper. His influence on the development of solid state physics extends to a deep understanding of many facets such as surface physics, of thermionic emission, of transport phenomena in semiconductors and of collective excitations in solids such as spin waves. He created the theoretical physics division at Bell Telephone Laboratory. Because of this, the total research effort at this institution and brought about much of the most original research in condensed matter physics during the latter half of the 20th century.
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Colossus was a set of computers developed by British codebreakers in the years 1943–1945 to help in the cryptanalysis of the Lorenz cipher. Colossus used thermionic valves (vacuum tubes) to perform Boolean and counting operations. Colossus is thus regarded as the world's first programmable, electronic, digital computer, although it was programmed by switches and plugs and not by a stored program. Colossus was designed by General Post Office (GPO) research telephone engineer Tommy Flowers to solve a problem posed by mathematician Max Newman at the Government Code and Cypher School (GC&CS;) at Bletchley Park.
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The lamp's electrodes are typically made of coiled tungsten and are coated with a mixture of barium, strontium and calcium oxides to improve thermionic emission. A germicidal lamp uses a low-pressure mercury-vapor glow discharge identical to that in a fluorescent lamp, but the uncoated fused quartz envelope allows ultraviolet radiation to transmit. Fluorescent lamp tubes are often straight and range in length from about for miniature lamps, to for high-output lamps. Some lamps have the tube bent into a circle, used for table lamps or other places where a more compact light source is desired.
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The gas ionization (or cold cathode) method of producing cathode rays used in Crookes tubes was unreliable, because it depended on the pressure of the residual air in the tube. Over time, the air was absorbed by the walls of the tube, and it stopped working. A more reliable and controllable method of producing cathode rays was investigated by Hittorf and Goldstein, and rediscovered by Thomas Edison in 1880. A cathode made of a wire filament heated red hot by a separate current passing through it would release electrons into the tube by a process called thermionic emission.
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They can be found in the power stages of radio and television transmitters, in musical instrument amplifiers (particularly electric guitar and bass amplifiers), in some high-end audio amplifiers, as detectors of optical and short wavelength radiation, and in sensitive equipment that must be "radiation-hard". In 1941 the London Power Company commemorated Fleming by naming a new 1,555 GRT coastal collier SS Ambrose Fleming. On 27 November 2004 a Blue Plaque presented by the Institute of Physics was unveiled at the Norman Lockyer Observatory, Sidmouth, to mark 100 years since the invention of the Thermionic Radio Valve.
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The last one is a krypton arc lamp, (shown for comparison). For low electrode wear the electrodes are usually made of tungsten, which has the highest melting point of any metal, to handle the thermionic emission of electrons. Cathodes are often made from porous tungsten filled with a barium compound, which gives low work function; the structure of cathode has to be tailored for the application. Anodes are usually made from pure tungsten, or, when good machinability is required, lanthanum-alloyed tungsten, and are often machined to provide extra surface area to cope with power loading.
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A cathode heater is a heated wire filament used to heat the cathode in a vacuum tube or cathode ray tube. The cathode element has to achieve the required temperature in order for these tubes to function properly. This is why older electronics often need some time to "warm up" after being powered on; this phenomenon can still be observed in the cathode ray tubes of some modern televisions and computer monitors. The cathode heats to a temperature that causes electrons to be 'boiled out' of its surface into the evacuated space in the tube, a process called thermionic emission.
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The entire rotor and shaft assembly is smaller in size than a pair of machines, and may not have any exposed drive shafts. Motor-generators can convert between any combination of DC and AC voltage and phase standards. Large motor-generator sets were widely used to convert industrial amounts of power while smaller units were used to convert battery power (6, 12 or 24 V DC) to a high DC voltage, which was required to operate vacuum tube (thermionic valve) equipment. For lower-power requirements at voltages higher than supplied by a vehicle battery, vibrator or "buzzer" power supplies were used.
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Vacuum ultraviolet (VUV) represents the most recent development in gas chromatography detectors. Most chemical species absorb and have unique gas phase absorption cross sections in the approximately 120–240 nm VUV wavelength range monitored. Where absorption cross sections are known for analytes, the VUV detector is capable of absolute determination (without calibration) of the number of molecules present in the flow cell in the absence of chemical interferences. Other detectors include the Hall electrolytic conductivity detector (ElCD), helium ionization detector (HID), infrared detector (IRD), photo-ionization detector (PID), pulsed discharge ionization detector (PDD), and thermionic ionization detector (TID).
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W. G. Pye & Co. Ltd was founded in 1896 in Cambridge by William Pye, superintendent of the Cavendish Laboratory workshop, as a part-time business making scientific instruments. By the outbreak of World War I in 1914, the company employed 40 people manufacturing instruments used for teaching and research. The war increased demand for such instruments and the War Office needed experimental thermionic valves. The manufacture of such components afforded the company the technical knowledge needed to develop the first wireless receiver when the first UK broadcasts were made by the British Broadcasting Company in 1922.
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TC electron emission will occur in one of two different regimes: temperature or space charge limited current flow. For temperature limited flow every electron that obtains enough energy to escape from the cathode surface is emitted, assuming the acceleration potential of the electron gun is large enough. In this case, the emission current is regulated by the thermionic emission process, given by the Richardson Dushman equation. In SCL electron current flow there are so many electrons emitted from the cathode that not all of them are accelerated enough by the electron gun to escape the space charge.
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Pentode symbol Electrodes, from top to bottom: anode (plate) suppressor grid screen grid control grid cathode heater (filament) A pentode is an electronic device having five active electrodes. The term most commonly applies to a three-grid amplifying vacuum tube (thermionic valve), which was invented by Gilles Holst and Bernhard D.H. Tellegen in 1926.G. Holst and B.D.H. Tellegen, "Means for amplifying electrical oscillations", US Patent 1945040, January 1934. The pentode consists of an evacuated glass envelope containing five electrodes in this order: a cathode heated by a filament, a control grid, a screen grid, a suppressor grid, and a plate (anode).
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Wade Allison was educated at Rugby School and then at Trinity College, Cambridge as an Open Exhibitioner in Natural Science. He gained a First Class in Part I of the Tripos, before taking Part II in Physics and Part III in Mathematics in 1963. At Oxford he studied for a DPhil in Particle Physics, on the way becoming the last student permitted to operate Oxford University's thermionic valve Ferranti Mercury computer. He was elected to a Research Lecturership (JRF) at Christ Church, Oxford in 1967 and a Fellow of the Royal Commission for the Exhibition of 1851.
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Radio interferometry started in the mid-1940s on the outskirts of Cambridge, but with funding from the Science Research Council and a corporate donation of £100,000 from Mullard Limited, a leading commercial manufacturer of thermionic valves. Construction of the Mullard Radio Astronomy Observatory commenced at Lords Bridge, a few kilometres to the west of Cambridge. The observatory was founded under Martin Ryle of the Radio-Astronomy Group of the Cavendish Laboratory, University of Cambridge and was opened by Sir Edward Victor Appleton on 25 July 1957. This group is now known as the Cavendish Astrophysics Group.
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After the turn of the century it was found that negative resistance mercury lamps could amplify, and were also tried in repeaters, with little success. The development of thermionic valves starting around 1902, provided an entirely electronic method of amplifying signals. The first practical version of such devices was the Audion triode, invented in 1906 by Lee De Forest, The link is to a reprint of the paper in the Scientific American Supplement, No. 1665, November 30, 1907, p.348-350, copied on Thomas H. White's United States Early Radio History website which led to the first amplifiers around 1912.
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Cold emission of electrons is relevant to semiconductors and superconductor physics. It is similar to thermionic emission, where electrons randomly jump from the surface of a metal to follow a voltage bias because they statistically end up with more energy than the barrier, through random collisions with other particles. When the electric field is very large, the barrier becomes thin enough for electrons to tunnel out of the atomic state, leading to a current that varies approximately exponentially with the electric field. These materials are important for flash memory, vacuum tubes, as well as some electron microscopes.
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Finnish inventor Eric Tigerstedt significantly improved on the original triode design in 1914, while working on his sound-on-film process in Berlin, Germany. Tigerstedt's innovation was to make the electrodes concentric cylinders with the cathode at the centre, thus greatly increasing the collection of emitted electrons at the anode. Irving Langmuir at the General Electric research laboratory (Schenectady, New York) had improved Wolfgang Gaede's high-vacuum diffusion pump and used it to settle the question of thermionic emission and conduction in a vacuum. Consequently, General Electric started producing hard vacuum triodes (which were branded Pliotrons) in 1915.
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Proper shielding is a complex subject due to a large number of variables involved. Semiconductors, especially integrated circuits, are extremely susceptible to the effects of EMP due to the close proximity of the PN junctions, but this is not the case with thermionic tubes (or valves) which are relatively immune to EMP. A Faraday cage does not offer protection from the effects of EMP unless the mesh is designed to have holes no bigger than the smallest wavelength emitted from a nuclear explosion. Large nuclear weapons detonated at high- altitudes also cause geomagnetically induced current in very long electrical conductors.
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Turing's colleagues at the NPL, not knowing about Colossus, thought that the engineering work to build a complete ACE was too ambitious, so the first version of the ACE that was built was the Pilot Model ACE, a smaller version of Turing's original design. Turing's assistant, Jim Wilkinson, worked on the logical design of the ACE and after Turing left for Cambridge in 1947, Wilkinson was appointed to lead the ACE group. The Pilot ACE had fewer than 1000 thermionic valves (vacuum tubes) compared to about 18,000 in the ENIAC.The ACE test assembly, H.D. Huskey, in Copeland (2005).
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1938 Zenith Model 12-S vacuum-tube console radio, capable of picking up mediumwave and shortwave AM transmissions. "All Wave" receivers could also pick up the third AM band, longwave stations. Unlike telegraph and telephone systems, which used completely different types of equipment, most radio receivers were equally suitable for both radiotelegraph and radiotelephone reception. In 1903 and 1904 the electrolytic detector and thermionic diode (Fleming valve) were invented by Reginald Fessenden and John Ambrose Fleming, respectively. Most important, in 1904–1906 the crystal detector, the simplest and cheapest AM detector, was developed by G. W. Pickard.
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A semiconductor device is an electronic component that relies on the electronic properties of a semiconductor material (primarily silicon, germanium, and gallium arsenide, as well as organic semiconductors) for its function. Semiconductor devices have replaced vacuum tubes in most applications. They use electrical conduction in the solid state rather than the gaseous state or thermionic emission in a vacuum. Semiconductor devices are manufactured both as single discrete devices and as integrated circuit (IC) chips, which consist of two or more devices—which can number from the hundreds to the billions—manufactured and interconnected on a single semiconductor wafer (also called a substrate).
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The name of both theorems stems from the work by Norman R. Campbell on thermionic noise, also known as shot noise, in vacuum tubes, which was partly inspired by the work of Ernest Rutherford and Hans Geiger on alpha particle detection, where the Poisson point process arose as a solution to a family of differential equations by Harry Bateman. In Campbell's work, he presents the moments and generating functions of the random sum of a Poisson process on the real line, but remarks that the main mathematical argument was due to G. H. Hardy, which has inspired the result to be sometimes called the Campbell–Hardy theorem.
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Closeup of the filament on a low pressure mercury gas discharge lamp showing white thermionic emission mix coating on the central portion of the coil acting as hot cathode. the coating is sputtered away every time the lamp starts, resulting in lamp failure. Low-mercury designs of lamps may fail when mercury is absorbed by the glass tube, phosphor, and internal components, and is no longer available to vaporize in the fill gas. Loss of mercury initially causes an extended run-up time to full light output, and finally causes the lamp to glow a dim pink when the argon gas takes over as the primary discharge.
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The battery terminal (electrode) that develops a positive voltage polarity (the carbon electrode in a dry cell) is called the cathode and the electrode with a negative polarity (zinc in a dry cell) is called the anode. This is the reverse of the terminology used in an electrolytic cell or thermionic vacuum tube. The reason is that the terms anode and cathode are defined by the direction of electric current, not by their voltage. The anode is the terminal through which conventional current (positive charge) enters the cell from the external circuit, while the cathode is the terminal through which conventional current leaves the cell and flows into the external circuit.
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The wiring on the rear of the computer in October 2018 Dr Bird and his team built a copy of Booth's machine in the BTM premises at Icknield Way Letchworth, which they called HEC 1. It was 1.5 m high by 3m wide by 0.5m deep and used simple circuits, with approximately 1000 ex-Government thermionic valves (vacuum tubes) mainly 6J6s which were B7G-based double triodes. The memory consisted of a diameter, wide drum rotating at 3000 rpm containing 32 tracks each storing sixteen 32-bit words giving a total of 2kilobytes. The drum had a special track from which the electronics were clocked.
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Setting the gate voltage to 0 V suppresses the tunneling current and enables only a lower current due to thermionic events. One of the main limitations of such a device is strongly related to the presence of this current that makes it difficult to properly switch it off. A clear advantage of such a device is that there is no need for channel doping and expensive technological steps like ion implantation and high temperature annealings can be avoided, keeping the thermal budget low. However the band bending due to the voltage difference between drain and gate often injects enough carriers to make impossible a proper switch off of the device.
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John Mathieson Dodds OBE (13 September 19051939 England and Wales Register - 15 October 1983) was a Scottish electrical engineer. He was educated at the University of Aberdeen and at the Technische Hochschule, Aachen, where he won a Dr Ing. in 1933. Dodds worked in the Research Department of Metropolitan- Vickers Electrical Co. in Trafford Park, Manchester, developing high-power thermionic valves, used in the transmitter part of equipment for radar stations for defence (Chain Home system), thereby making a significant contribution to Britain's survival in World War II. He was appointed an Officer of the Order of the British Empire (OBE) in the 1944 Birthday Honours.
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During his doctoral studies, Jain assisted his mentor, K. S. Krishnan, the co- discoverer of the Raman Effect, on the thermal conductivity of solids. It was during this time, the duo developed a methodology for the measurement of thermal conductivity in solids at high temperatures which was published by them in an article, Thermionic Constants of Metals and Semiconductors. II. Metals of the First Transition Group in 1952 in Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences and later explained further by way of another article, Determination of thermal conductivities at high temperatures in British Journal of Applied Physics in 1954.
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Capillary action through synthetic mesh is the result of the intermolecular attraction between moisture and semi-synthetic polymers, causing a current of thermionic energy through a specific pathway within a mesh material. The combination of the adhesive forces and the surface tension that arises from cohesion produces the characteristic upward curve in a fluid, such as water. Capillarity is the result of cohesion of water molecules and adhesion of those molecules to the solid material forming the void. As the edges of the material are brought closer together, such as in a very narrow path, the interaction causes the liquid to be drawn away from the original source.
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In November 1953 Richard Grimsdale and Douglas Webb of Manchester University first demonstrated their prototype transistorized computer using 92 point-contact transistors and 550 diodes in order to test the suitability of transistors in improving the reliability of the Manchester Mark 1 computer. This machine was similar to the Mark I, except that it did not include Williams tubes and used only the magnetic drum for main memory. The machine was based on a 48-bit word, although 4 bits were used for timing and thus not available for program use. This machine used thermionic valves to generate a clock frequency of 125 kHz.
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Trautonium, 1928 The earliest synthesizers used a variety of thermionic-valve (vacuum tube) and electro-mechanical technologies. While some electric instruments were produced in bulk, such as Georges Jenny's Ondioline, the Hammond organ, and the Trautonium, many of these would not be considered synthesizers by the standards of later instruments. However, some individual studios and instruments achieved a high level of sophistication, such as the Trautonium of Oskar Sala, the Electronium of Raymond Scott, and the ANS synthesizer of Evgeny Murzin. Another notable early instrument is the Hammond Novachord, first produced in 1938, which had many of the same features as later analog synthesizers.
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BBC Elstree Studio C in July 1991. The last programme in the world to use EMI 2001s to record images was EastEnders The EMI 2001 Broadcast studio camera was an early, very successful British made Plumbicon studio camera that included the lens within the body of the camera. Four 30 mm tubes allowed one tube to be dedicated solely to producing a relatively high resolution monochrome signal, with the other three tubes each providing red, green or blue signals. Even though semiconductors were used in most of the camera, the highly sensitive head amplifiers still used thermionic valves in the first generation of the design.
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After the EMI board granted approval for the new camera, in late 1964, work on it progressed rapidly. The camera was to use four Plumbicon pick-up tubes, to use solid state circuitry, include a zoom lens as standard and to use prism optics. After the late start, the first fully operational prototype was shown to the BBC and others in 1966, only just in time to meet BBC time-scales for the introduction of their new colour service. Early cameras used thermionic valves (vacuum tubes) in the first stages of the head amplifiers but later FET amplifiers were introduced, such cameras being designated type 2001/1.
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For high-end audio, where cost is not the primary consideration, valve amplifiers have remained popular and indeed during the 1990s made a commercial resurgence. Circuits designed since then in most cases remain similar to circuits from the valve age, but benefit from advances in ancillary component quality (including capacitors) as well as general progress across the electronics industry which gives designers increasingly powerful insight into circuit operation. Solid-state power supplies are more compact, efficient, and can have very good regulation. Semiconductor power amplifiers do not have the severe limitations on output power imposed by thermionic devices; accordingly loudspeaker design has evolved in the direction of smaller.
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Adding one or more control grids within the tube allows the current between the cathode and anode to be controlled by the voltage on the grids. These devices became a key component of electronic circuits for the first half of the twentieth century. They were crucial to the development of radio, television, radar, sound recording and reproduction, long-distance telephone networks, and analog and early digital computers. Although some applications had used earlier technologies such as the spark gap transmitter for radio or mechanical computers for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, and created the discipline of electronics.
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This is the so- called "tetrode kink" and is an example of negative resistance which can itself cause instability.Introduction to Thermionic Valves (Vacuum Tubes) , Colin J. Seymour The otherwise undesirable negative resistance was exploited to produce a simple oscillator circuit only requiring connection of the plate to a resonant LC circuit to oscillate; this was effective over a wide frequency range. The so-called dynatron oscillator thus operated on the same principle of negative resistance as the tunnel diode oscillator many years later. Another undesirable consequence of secondary emission is that in extreme cases enough charge can flow to the screen grid to overheat and destroy it.
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The term "solid state" became popular in the beginning of the semiconductor era in the 1960s to distinguish this new technology based on the transistor, in which the electronic action of devices occurred in a solid state, from previous electronic equipment that used vacuum tubes, in which the electronic action occurred in a gaseous state. A semiconductor device works by controlling an electric current consisting of electrons or holes moving within a solid crystalline piece of semiconducting material such as silicon, while the thermionic vacuum tubes it replaced worked by controlling current conducted by a gas of particles, electrons or ions, moving in a vacuum within a sealed tube.
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The replacement of the relatively fragile thermionic valve (vacuum tube) by the smaller, lighter-weight, cooler-running, less expensive, more robust, and less power-hungry transistor also accelerated the sale of consumer high-fidelity "hi-fi" sound systems from the 1960s onward. In the 1950s, most record players were monophonic and had relatively low sound quality. Few consumers could afford high-quality stereophonic sound systems. In the 1960s, American manufacturers introduced a new generation of "modular" hi-fi components — separate turntables, pre-amplifiers, amplifiers, both combined as integrated amplifiers, tape recorders, and other ancillary equipment like the graphic equaliser, which could be connected together to create a complete home sound system.
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Although it gives the correct direction of rectification, it has also been proven that the Mott theory and its Schottky-Davydov extension gives the wrong current limiting mechanism and wrong current-voltage formulae in silicon metal/semiconductor diode rectifiers. The correct theory was developed by Hans Bethe and reported by him in a M.I.T. Radiation Laboratory Report dated November 23, 1942. In Bethe's theory, the current is limited by thermionic emission of electrons over the metal–semiconductor potential barrier. Thus, the appropriate name for the metal–semiconductor diode should be the Bethe diode, instead of the Schottky diode, since the Schottky theory does not predict the modern metal–semiconductor diode characteristics correctly.
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Although it resembles a vacuum tube in appearance, its operation does not depend on thermionic emission of electrons from a heated cathode. It is therefore called a cold-cathode tube (a form of gas-filled tube), and is a variant of the neon lamp. Such tubes rarely exceed even under the most severe of operating conditions in a room at ambient temperature. Vacuum fluorescent displays from the same era use completely different technology—they have a heated cathode together with a control grid and shaped phosphor anodes; Nixies have no heater or control grid, typically a single anode (in the form of a wire mesh, not to be confused with a control grid), and shaped bare metal cathodes.
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A 65-watt fluorescent lamp starting on a semi-resonant start circuit A semi-resonant start circuit diagram The semi- resonant start circuit was invented by Thorn Lighting for use with T12 fluorescent tubes. This method uses a double wound transformer and a capacitor. With no arc current, the transformer and capacitor resonate at line frequency and generate about twice the supply voltage across the tube, and a small electrode heating current.Thorn Lighting Technical Handbook This tube voltage is too low to strike the arc with cold electrodes, but as the electrodes heat up to thermionic emission temperature, the tube striking voltage falls below that of the ringing voltage, and the arc strikes.
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Sir John Ambrose Fleming FRS (29 November 1849 – 18 April 1945) was an English electrical engineer and physicist who invented the first thermionic valve or vacuum tube, designed the radio transmitter with which the first transatlantic radio transmission was made, and also established the right-hand rule used in physics. He was the eldest of seven children of James Fleming DD (died 1879), a Congregational minister, and his wife Mary Ann, at Lancaster, Lancashire, and baptised on 11 February 1850. A devout Christian, he once preached at St Martin-in-the-Fields in London on evidence for the resurrection. In 1932, he and Douglas Dewar and Bernard Acworth helped establish the Evolution Protest Movement.
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Norton 2008, pp. 123–125. Although capable of aiming the cannons, the gunners' primary purpose was simply to load them with the 110 rounds of ammunition stored in each nacelle. The crew of five included the pilot and gunners; a copilot/navigator who doubled as a fire-control officer, using a Sperry Instruments "Thermionic" fire control system (originally developed for anti-aircraft cannon) combined with a gyro-stabilised and an optical sight to aim the weapons; and a radio operator/gunner armed with a pair of machine guns stationed at mid-fuselage waist blisters for defense against attack from the rear. An unusual feature of the Airacuda was the main door for entry.
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In 1914 Hull joined the General Electric Research Laboratory (GERL) in Schenectady, New York and remained there until his retirement in 1949. During 1916, Hull began investigation into the use of magnetic control of thermionic valves (vacuum tubes) as an alternative to grid or electrostatic control and he had tested successfully magnetic control by applying a magnetic field parallel to the axis of the tube. Initially, Hull's work on these novel electron tubes was part of an effort at General Electric to develop amplifiers and oscillators that might be used to circumvent the vacuum- tube triode patents of Lee de Forest and Edwin Armstrong. Hull was promoted to assistant director of the GERL in 1928.
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The main source of plasma within the LAPD is produced via discharge from the barium oxide (BaO) coated cathode, which emits electrons via thermionic emission. The cathode is located near the end of the LAPD and is made from a thin nickel sheet, uniformly heated to roughly 900 °C. The circuit is closed by a molybdenum mesh anode a short distance away. Typical discharge currents are in the range of 3-8 kiloamperes at 60-90 volts, supplied by a custom- designed transistor switch backed by a 4-farad capacitor bank. A secondary cathode source made of lanthanum hexaboride (LaB6) was developed in 2010 to provide a hotter and denser plasma when required.
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William George Pye The lives of William George and Harold John Pye, (born 27 October 1869 at Battersea, London) founded W G Pye in 1896, a company which manufactured scientific and optical equipment. The firm prospered during World War I by manufacturing specialist equipment such as gun sights. After the war new products needed to be found and the company started to manufacture radio parts such as thermionic valves and eventually a radio. Harold John Pye, who was the son of William then joined the firm and helped to develop a new radio which proved so successful that the radio manufacturing side of W G Pye and the rights to the name Pye Radio was bought.
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This was demonstrated during the Shuttle orbiter's TSS-1R mission, when the shuttle itself was used as a large plasma contactor to provide over an ampere of current. Improved methods include creating an electron emitter, such as a thermionic cathode, plasma cathode, plasma contactor, or field electron emission device. Since both ends of the tether are "open" to the surrounding plasma, electrons can flow out of one end of the tether while a corresponding flow of electrons enters the other end. In this fashion, the voltage that is electromagnetically induced within the tether can cause current to flow through the surrounding space environment, completing an electrical circuit through what appears to be, at first glance, an open circuit.
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Oskar Heil and Agnesa Arsenjewa-Heil in their pioneering paper developed the concept of the velocity-modulated tube, in which a beam of electrons could be made to form into "bunches" and thereby generate with reasonable efficiency radio waves of considerably higher frequency and power than were possible with conventional vacuum tubes/thermionic valves. This resulted in production of the "Heil tube", the first truly-practicable microwave generator, which slightly predated the (independent) invention of the klystron and subsequently the reflex klystron based on the same operating principle. These devices were a significant milestone in the development of microwave technology (particularly radar), and velocity-modulated tubes are still very much in use at the present day.
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Commercial implementation began in 1934 as cathode ray tube screens became brighter, increasing the level of flicker caused by progressive (sequential) scanning.R.W. Burns, Television: An International History of the Formative Years, IET, 1998, p. 425. . In 1936, when the UK was setting analog standards, early thermionic valve based CRT drive electronics could only scan at around 200 lines in 1/50 of a second (i.e. approximately a 10kHz repetition rate for the sawtooth horizontal deflection waveform). Using interlace, a pair of 202.5-line fields could be superimposed to become a sharper 405 line frame (with around 377 used for the actual image, and yet fewer visible within the screen bezel; in modern parlance, the standard would be "377i").
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Those unfamiliar with sealed vacuum devices, such as vacuum tubes/thermionic valves, high- pressure sodium lamps or some types of metal-halide lamps, often notice the shiny flash getter deposit and mistakenly think it is a sign of failure or degradation of the device. Contemporary high-intensity discharge lamps tend to use non-evaporable getters rather than flash getters. Those familiar with such devices can often make qualitative assessments as to the hardness or quality of the vacuum within by the appearance of the flash getter deposit, with a shiny deposit indicating a good vacuum. As the getter is used up, the deposit often becomes thin and translucent, particularly at the edges.
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The filament itself may be the cathode, or more commonly (as shown here) used to heat a separate metal tube which serves as the cathode. A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode vacuum tube or thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from cathode to plate. A semiconductor diode, the most commonly used type today, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals.
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When a metal object is placed in a vacuum and is heated to incandescence, the energy is sufficient to cause electrons to "boil" away from the surface atoms and surround the metal object in a cloud of free electrons. This is called thermionic emission. The resulting cloud is negatively charged, and can be attracted to any nearby positively charged object, thus producing an electric current which passes through the vacuum. Space charge can result from a range of phenomena, but the most important are: # Combination of the current density and spatially inhomogeneous resistance # Ionization of species within the dielectric to form heterocharge # Charge injection from electrodes and from a stress enhancement # Polarization in structures such as water trees.
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This is the saturation region, and the JFET is normally operated in this constant-current region where device current is virtually unaffected by drain-source voltage. The JFET shares this constant-current characteristic with junction transistors and with thermionic tube (valve) tetrodes and pentodes. Constriction of the conducting channel is accomplished using the field effect: a voltage between the gate and the source is applied to reverse bias the gate-source pn-junction, thereby widening the depletion layer of this junction (see top figure), encroaching upon the conducting channel and restricting its cross-sectional area. The depletion layer is so- called because it is depleted of mobile carriers and so is electrically non- conducting for practical purposes.
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In 1968 Izatt was on a train ride home when he stopped in Chicago to meet with the physiologist George Eisenman who informed Izatt about Pedersen's paper on crown ethers published only months earlier. Izatt was looking forward to the possibilities of studying these crown ethers with his thermionic titration technique. Izatt called Pedersen and was the first scientist not at DuPont to meet with Pedersen about his discovery and Pedersen supplied him with a sample of his new crown ether compound. Izatt's work on molecular recognition was greatly influenced by his interaction with Pedersen. In Izatt's last visit with Pedersen prior to his death in 1988 he found a personal letter written by Pedersen that stated, “Most men achieve ‘Immortality’ through their progeny.
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Section of a typical Australian late 1930s radio, showing the point to point construction between components. Point-to-point construction is a non- automated method of construction of electronics circuits widely used before the use of printed circuit boards (PCBs) and automated assembly gradually became widespread following their introduction in the 1950s. Circuits using thermionic valves (vacuum tubes) were relatively large, relatively simple (the number of large, hot, expensive devices which needed replacing was minimised), and used large sockets, all of which made the PCB less obviously advantageous than with later complex semiconductor circuits. Point-to-point construction is still widespread in power electronics where components are bulky and serviceability is a consideration, and to construct prototype equipment with few or heavy electronic components.
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Included in this portion of the syllabus are thermionic emissions with their characteristic curves, diodes, triodes and multi- electrode valves; and the use of valves as rectifiers, oscillators, amplifiers, detectors and frequency changers, stabilisation and smoothing. Radio receivers is the fourth topic that covers the principles and operation of TRF receivers and Superheterodyne receivers, CW reception; with receiver characteristics such as sensitivity, selectivity and fidelity; Adjacent- channel interference and image interference; AGC and squelch; and signal to noise ratio (S/R). Similarly, the next topic on transmitters covers the principles and operation of low power transmitters; oscillators such as the Colpitts oscillator, Hartley oscillator, crystal oscillators, and stability of oscillators. The last three topics deal with radio propagation, aerials, and frequency measurement.
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In Europe, the principal method of numbering vacuum tubes ("thermionic valves") was the nomenclature used by the Philips company and its subsidiaries Mullard in the UK, Valvo(de, it) in Germany, Radiotechnique (Miniwatt-Dario brand) in France, and Amperex in the United States, from 1934 on. Adhering manufacturers include AEG (de), CdL (1921, French Mazda brand), CIFTE (fr, Mazda-Belvu brand), EdiSwan (British Mazda brand), Lorenz (de), MBLE(fr, nl) (be, Adzam brand), RCA (us), RFT(de, sv) (de), Siemens (de), Telefunken (de), Tesla (cz), Toshiba (ja), Tungsram (hu), and Unitra (pl; Dolam, Polam, Telam brands). This system allocated meaningful codes to tubes based on their function and became the starting point for the Pro Electron naming scheme for active devices (including tubes and transistors).
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In 1926 he employed his electronics skills to construct an amplifier using thermionic valves (vacuum tubes) for very small electrical currents. It was realized that such devices could be used in the detection and counting of Alpha particles in the nuclear disintegration experiments then being undertaken by Rutherford, who encouraged him to devote his attention to the construction of a reliable valve amplifier and methods of registering and counting particles. Wynn-Williams' scale-of-two counter (with permission of the Cavendish Laboratory, University of Cambridge, UK) There followed a series of brilliant contributions to the armamentarium of nuclear physics. In 1929–30, with H. M. Cave and F. A. B. Ward he designed and constructed a binary prescaler for an electro-mechanical counter using thyratrons.
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Under the command of a new Führer (who is referred to as "Chancellor", and his real name is never revealed), Operation Sealion succeeds and the Nazis successfully conquer Britain, sparking a cold war between the Allied Powers and Germany. The Fallout series of computer role-playing games is set in a divergent America, where history after World War II diverges from the real world to follow a retro-futuristic timeline. For example, fusion power was invented quite soon after the end of the war, but the transistor was never developed. The result was a future that has a 1950s 'World of Tomorrow' feel to it, with extremely high technology such as artificial intelligence implemented with thermionic valves and other technologies now considered obsolete.
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The satellite was part of the Soviet Union's RORSAT programme, a series of reconnaissance satellites which observed ocean traffic, including surface vessels and nuclear submarines, using active radar. It was assigned the Kosmos number 954 and was launched on 18 September 1977 at 13:55 UTC from the Baikonur Cosmodrome, on a Tsyklon-2 carrier rocket. With an orbital inclination of 65°, a periapsis of and apoapsis of , it orbited the Earth every 89.5 minutes. Powered by a liquid sodium–potassium thermionic converter driven by a nuclear reactor containing around of uranium-235, the satellite was intended for long-term on-orbit observation, but by December 1977 the satellite had deviated from its designed orbit and its flightpath was becoming increasingly erratic.
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So we see vc, ve, and vb, as well as ic, ie, and ib. Using these conventions, in a common emitter amplifier, the ratio ''''' represents the small-signal voltage gain at the transistor and ''''' the small-signal trans-resistance from which the name transistor is derived by contraction. In this convention, vi and vo usually refer to the external input and output voltages of the circuit or stage. Similar conventions were applied to circuits involving vacuum tubes or thermionic valves as they were known outside of the U.S. Therefore, we see VP, VK, and VG referring to plate (or anode outside of the U.S.), cathode (note K, not C) and grid voltages in analyses of vacuum triode, tetrode, and pentode circuits.
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Drilling using electrical plasma An electric arc is an electrical breakdown of a gas that produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air or gas. An arc discharge is characterized by a lower voltage than a glow discharge, and relies on thermionic emission of electrons from the electrodes supporting the arc. The electric arc is influenced by factors such as: the gas flow, inner and outer magnetic fields, and construction elements of the chamber which confine the arc. The development of highly effective plasma torches to be used as a source of the thermal plasma, demands a deep understanding of a wide spectrum of the processes taking place in the discharge chamber.
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Thermionic diode rectifiers were widely used in power supplies in vacuum tube consumer electronic products, such as phonographs, radios, and televisions, for example the All American Five radio receiver, to provide the high DC plate voltage needed by other vacuum tubes. "Full-wave" versions with two separate plates were popular because they could be used with a center-tapped transformer to make a full-wave rectifier. Vacuum tube rectifiers were made for very high voltages, such as the high voltage power supply for the cathode ray tube of television receivers, and the kenotron used for power supply in X-ray equipment. However, compared to modern semiconductor diodes, vacuum tube rectifiers have high internal resistance due to space charge and therefore high voltage drops, causing high power dissipation and low efficiency.
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Holweck was born on 21 July 1890 to a family from the Alsace Region who had opted to remain French at the end of the Franco-Prussian war in 1870.Vacuum Science and Technology: Pioneers of the 20th Century (AVS Classics in Vacuum Science and Technology), Paul A. Redhead (Editor), American Institute of Physics Publishing, 1997. He studied at the École supérieure de physique et de chimie industrielles de la ville de Paris (ESPCI), ESPCI ParisTech Alumni 1910 where he graduated top of his class in engineering physics and became personal assistant to Marie Curie. During his military service he worked under the wireless telegraphy pioneer Gustave- Auguste Ferrié at the Eiffel Tower radio station, and by 1914 he had produced his first patent, relating to thermionic tubes.
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The motor was further upgraded from the Magpie III to the new Linnet which offered significantly higher performance and boosted the typical top speed of the missile from Mach 2.4 to 3.2 whilst almost doubling effective range to . The adoption of transistorized circuits in place of the former thermionic valves eliminated the need for cooling the electronics, as well as making the guidance section significantly smaller. This allowed the warhead to be moved from its former position near the tail to the midsection, which also allowed it to grow in size and weight, replacing the former blast-fragmentation type with an expanding-rod system that was significantly deadlier. This also allowed the steering fin actuators to be placed at the rear of the missile, eliminating the pushrods and their associated complexity.
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Fig. 1: Band diagram of p-n junction in standard solar cell In a basic Schottky-junction (Schottky-barrier) solar cell, an interface between a metal and a semiconductor provides the band bending necessary for charge separation. Traditional solar cells are composed of p-type and n-type semiconductor layers sandwiched together, forming the source of built-in voltage (a p-n junction). Due to differing energy levels between the Fermi level of the metal and the conduction band of the semiconductor, an abrupt potential difference is created, instead of the smooth band transition observed across a p-n junction in a standard solar cell, and this is a Schottky height barrier. Although vulnerable to higher rates of thermionic emission, manufacturing of Schottky barrier solar cells proves to be cost-effective and industrially scalable.
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In the early days of colour television (from the mid 1950s to the early 1960s) studio cameras were heavy and hot-running because of the vacuum tube (thermionic valve) circuitry that they contained, in addition to three large image orthicon pick-up tubes. With these cameras there was always a tendency for the three coloured images to drift out of registration, over time, giving a consequential loss of picture sharpness. In 1962, in order to address these stability problems, RCA announced their prototype four-tube camera. The aims of the designers of the camera were, firstly, to produce a camera that was more tolerant to mis-registration and, secondly, to achieve a lighter camera by using smaller vidicon tubes to replace some of the large heavy IO tubes.
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Becquerel paid special attention to the study of light, investigating the photochemical effects and spectroscopic characters of solar radiation and the electric arc light, and the phenomena of phosphorescence, particularly as displayed by the sulfides and by compounds of uranium. It was in connection with these latter inquiries that he devised his phosphoroscope, an apparatus which enabled the interval between exposure to the source of light and observation of the resulting effects to be varied at will and accurately measured. He investigated the diamagnetic and paramagnetic properties of substances and was keenly interested in the phenomena of electrochemical decomposition, accumulating much evidence in favor of Faraday's law of electrolysis and proposing a modified statement of it which was intended to cover certain apparent exceptions. In 1853, Becquerel discovered thermionic emission.
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Like bosons that can be condensed to form Bose–Einstein condensates, Rydberg matter can be condensed, but not in the same way as bosons. The reason for this is that Rydberg matter behaves similarly to a gas, meaning that it cannot be condensed without removing the condensation energy; ionisation occurs if this is not done. All solutions to this problem so far involve using an adjacent surface in some way, the best being evaporating the atoms of which the Rydberg matter is to be formed from and leaving the condensation energy on the surface. Using caesium atoms, graphite-covered surfaces and thermionic converters as containment, the work function of the surface has been measured to be 0.5 eV, indicating that the cluster is between the ninth and fourteenth excitation levels.
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Supplied by Mullard & Brimar. CV509 – 6V6G CV510 – 6V6 CV511 – 6V6GT & 6V6GTY The British GPO also used their own VT (Valve - Thermionic) numbering system VT196 = CV509 = 6V6G – General Post Office (GPO) Swedish Military supplier Bofors, had tubes made by Standard Radiofabrik (SRF) at the Ulvsunda plant in Stockholm. 5S2D - Premium, ruggedized 6V6GT with triple micas, low loss micanol brown base. Other tubes cited as being equivalent 6P6S (6П6С in Cyrillic.) Also 6П2 - In the Soviet Union a version of the 6V6GT was produced since the late 1940s which appears to be a close copy of the 1940s Sylvania-issue 6V6GT – initially under its American designation (in both Latin and Cyrillic lettering), but later, the USSR adopted its own system of designations. 6P11S (6П11С in Cyrillic.) = 6П6С-Y2 - Military consignment, ruggedized 6P6S.
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In systems using alternating current but without separate anode structures, the electrodes alternate as anodes and cathodes, and the impinging electrons can cause substantial localized heating, often to red heat. The electrode may take advantage of this heating to facilitate the thermionic emission of electrons when it is acting as a cathode. (Instant-start fluorescent lamps employ this aspect; they start as cold-cathode devices, but soon localized heating of the fine tungsten-wire cathodes causes them to operate in the same mode as hot-cathode lamps.) This aspect is problematic in the case of backlights used for LCD TV displays. New energy-efficiency regulations being proposed in many countries will require variable backlighting; variable backlightling also improves the perceived contrast range, which is desirable for LCD TV sets.
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Thermotunnel cooling is similar to thermionic emission cooling in that fast moving electrons carry heat across a gap but cannot return due to a voltage difference. The problem with using thermal electrons to carry heat is the fact that, due to the high work function of metals, which are the only practical emitters, the lowest cooling temperate is around 600 °C - clearly not useful except in the most unusual applications. Thermotunnel cooling avoids this problem by making the gap narrow enough that electrons can tunnel across the gap, carrying the heat with them. The problem with this approach has been getting two surfaces near enough that they can tunnel over a large area, yet not touch at any point, which would short the device out preventing it from doing any useful cooling.
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After emission, a charge that is equal in magnitude and opposite in sign to the total charge emitted is initially left behind in the emitting region. But if the emitter is connected to a battery, the charge left behind is neutralized by charge supplied by the battery as the emitted charge carriers move away from the emitter, and finally the emitter will be in the same state as it was before emission. The classical example of thermionic emission is that of electrons from a hot cathode into a vacuum (also known as thermal electron emission or the Edison effect) in a vacuum tube. The hot cathode can be a metal filament, a coated metal filament, or a separate structure of metal or carbides or borides of transition metals.
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Photon- enhanced thermionic emission (PETE) is a process developed by scientists at Stanford University that harnesses both the light and heat of the sun to generate electricity and increases the efficiency of solar power production by more than twice the current levels. The device developed for the process reaches peak efficiency above 200 °C, while most silicon solar cells become inert after reaching 100 °C. Such devices work best in parabolic dish collectors, which reach temperatures up to 800 °C. Although the team used a gallium nitride semiconductor in its proof-of-concept device, it claims that the use of gallium arsenide can increase the device's efficiency to 55–60 percent, nearly triple that of existing systems, and 12–17 percent more than existing 43 percent multi-junction solar cells.
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Although thermionic emission was originally reported in 1873 by Frederick Guthrie, it was Thomas Edison's apparently independent discovery of the phenomenon in 1883 that became well known. Although Edison was aware of the unidirectional property of current flow between the filament and the anode, his interest (and patentThomas A. Edison "Electrical Indicator", Issue date: 1884) concentrated on the sensitivity of the anode current to the current through the filament (and thus filament temperature). Little practical use was ever made of this property (however early radios often implemented volume controls through varying the filament current of amplifying tubes). It was only years later that John Ambrose Fleming utilized the rectifying property of the diode tube to detect (demodulate) radio signals, a substantial improvement on the early cat's-whisker detector already used for rectification.
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Examples of low power triodes from 1918 (left) to miniature tubes of the 1960s (right) A triode is an electronic amplifying vacuum tube (or valve in British English) consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate (anode). Developed from Lee De Forest's 1906 Audion, a partial vacuum tube that added a grid electrode to the thermionic diode (Fleming valve), the triode was the first practical electronic amplifier and the ancestor of other types of vacuum tubes such as the tetrode and pentode. Its invention founded the electronics age, making possible amplified radio technology and long-distance telephony. Triodes were widely used in consumer electronics devices such as radios and televisions until the 1970s, when transistors replaced them.
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De Forest's first commercial Audion receiver, the RJ6 which came out in 1914. The Audion tube was always mounted upside down, with its delicate filament loop hanging down, so it did not sag and touch the other electrodes in the tube. The first amplifying vacuum tube, the Audion, a crude triode, was invented in 1906 by Lee De Forest as a more sensitive detector for radio receivers, by adding a third electrode to the thermionic diode detector, the Fleming valve. McNicol, Donald (1946) Radio's Conquest of Space, p. 254-259 The link is to a reprint of the paper in the Scientific American Supplement, No. 1665, November 30, 1907, p.348-350, copied on Thomas H. White's United States Early Radio History website It was not widely used until its amplifying ability was recognized around 1912.
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The current through the filaments causes them to heat up and emit electrons into the tube gas by thermionic emission. In the starter, the touching contacts short out the voltage sustaining the glow discharge, extinguishing it so the gas cools down and no longer heats the bi-metallic switch, which opens within a second or two. The current through the filaments and the inductive ballast is abruptly interrupted, leaving the full line voltage applied between the filaments at the ends of the tube and generating an inductive kick which provides the high voltage needed to start the lamp. The lamp will fail to strike if the filaments are not hot enough, in which case the cycle repeats; several cycles are usually needed, which causes flickering and clicking during starting (older thermal starters behaved better in this respect).
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Julius Edgar Lilienfeld proposed the concept of a field-effect transistor in 1925. The thermionic triode, a vacuum tube invented in 1907, enabled amplified radio technology and long-distance telephony. The triode, however, was a fragile device that consumed a substantial amount of power. In 1909, physicist William Eccles discovered the crystal diode oscillator. Austro-Hungarian physicist Julius Edgar Lilienfeld filed a patent for a field-effect transistor (FET) in Canada in 1925, which was intended to be a solid-state replacement for the triode.Vardalas, John (May 2003) Twists and Turns in the Development of the Transistor IEEE-USA Today's Engineer.Lilienfeld, Julius Edgar, "Method and apparatus for controlling electric current" January 28, 1930 (filed in Canada 1925-10-22, in US October 8, 1926). Lilienfeld also filed identical patents in the United States in 1926 and 1928.
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Wynn-Williams had obtained his PhD at Cambridge University for his work at the Cavendish Laboratory with Sir Ernest Rutherford. In 1926 he had constructed an amplifier using thermionic valves (vacuum tubes) for the very small electrical currents arising from detectors in their nuclear disintegration experiments. Rutherford had got him to devote his attention to the construction of a reliable valve amplifier and methods of registering and counting these particles. The counter used gas-filled Thyratron tubes which are bi-stable devices. The counters that Wynn-Williams designed for Heath Robinson, and subsequently for the Colossus computers used thyratrons to count units of 1, 2, 4, 8; high speed relays to count units of 16, 32, 48, 64; and slower relays to count 80, 160, 240, 320, 400, 800, 1200, 1600, 2000, 4000, 6000, and 8000.
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Before the development of power semiconductors and allied technologies, one way to convert the voltage of a DC supply to a higher voltage, for low-power applications, was to convert it to AC by using a vibrator, followed by a step- up transformer and rectifier. For higher power an electric motor was used to drive a generator of the desired voltage (sometimes combined into a single "dynamotor" unit, a motor and generator combined into one unit, with one winding driving the motor and the other generating the output voltage). These were relatively inefficient and expensive procedures used only when there was no alternative, as to power a car radio (which then used thermionic valves/tubes requiring much higher voltages than available from a 6 or 12 V car battery). The introduction of power semiconductors and integrated circuits made it economically viable to use techniques as described below.
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Both the Manchester University Transistor Computer and the Bell Laboratories TRADIC were demonstrated incorporating transistors before CADET was operational, although both required some thermionic valves to supply their faster clock power, so they were not fully transistorised. In April 1955 IBM announced the IBM 608 transistor calculator, which they claim was "the first all solid-state computing machine commercially marketed"IBM Archives, 1955 and "the first completely transistorized computer available for commercial installation",IBM Archives: IBM 608 calculator and which may have been demonstrated in October 1954, before the CADET. By 1956, Brian Flowers, head of the theoretical physics division at AERE, was convinced that the CADET provided insufficient computing power for the needs of his numerical analysts and ordered a Ferranti Mercury computer. In 1958, Mercury number 4 became operational at AERE to accompany the CADET for another two years before the CADET was retired after four years' operation.
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The space charge grid tube was the first type of tetrode to appear. In the course of his research into the action of the "audion" triode tube of Lee de Forest, Irving Langmuir found that the action of the heated thermionic cathode was to create a space charge, or cloud of electrons, around the cathode. This cloud acted as a virtual cathode. With low applied anode voltage, many of the electrons in the space charge returned to the cathode, and did not contribute to the anode current; only those at its outer limit would be affected by the electric field due to the anode, and would be accelerated towards it. However, if a grid bearing a low positive applied potential (about 10V) were inserted between the cathode and the control grid, the space charge could be made to extend further away from the cathode.
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The MiG-21P and MiG-21PF were the first MiG-21's to be equipped with a real radar that would enable them to search, track and intercept targets by night and in foul weather: the RP-21 Sapfir ('Sapphire') radar, which was given the NATO codename of "Spin Scan-A." The RP-21 Sapfir replaced the MiG-21F-13's SRD-5M Kvantum ('Quantum') ranging- and gun-radar. RP-21 featured a mechanically steered and gyroscopic stabilised radar dish, and had a thermionic valve (vacuum tube) circuit. In theory it was able to detect fighter-sized targets from a range of 20 km, and lock on to them at a range of 10 km though in practice this got reduced to 13 km and 7 km respectively. The associated weapon was the Vympel K-13 infrared guided air-to-air missile, also known as R-3S, object 310 or AA-2 "Atoll-A" by NATO, already in use with the older SRD-5M radar.
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After his time at Woods Hole, Otto and his wife Viola moved to London to continue his research with nerve impulses under Professor A.V. Hill – Nobel Prize winner and founder of biophysics. It was during this time that Schmitt published a report on a novel bit of circuitry that would win him a lasting degree of fame. Otto originally named it the “thermionic trigger.” As a testament to the profound impact that Otto and his device had on electronics, it is still widely referred to as the “Schmitt trigger.” Schmitt spent two years in his postdoctoral position, even though his fellowship funding on lasted for one year; Professor Hill, recognizing Otto's talents, sought out additional sources of funding to keep Otto in London for as long as he could. Schmitt's next opportunity would bring him back the U.S. Once again, Otto's older brother Francis would play a vital role in Otto's career.
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S.P. Austin & Co had built her in 1924 for W.B. Nisbet and the Tanfield Steamship Company of Newcastle-upon-Tyne, who named her after the village of New Lambton, County Durham. She was a larger coaster, not a flatiron, so she could not reach Battersea but could take larger loads to Deptford. New Lambton was torpedoed and sunk on the same day and in the same part of the North Sea as Sir Joseph Swan (see above). SS Ambrose Fleming was a 1,222 GRT flatiron launched at Burntisland in February 1941 and completed in April. She was named after the electrical engineer Sir John Ambrose Fleming (1849–1945), who invented the thermionic valve. Ambrose Fleming had a very short life, for on 28 April 1941 a German E-boat torpedoed and sank her off Cromer. 11 crew members were lost and 11 were rescued. SS Sir Leonard Pearce (II) was a 1,580 GRT flatiron launched at Burntisland in August 1941.
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Bush's idea for the memex extended far beyond a mechanism which might augment the research of one individual working in isolation. In Bush's idea, the ability to connect, annotate, and share both published works and personal trails would profoundly change the process by which the "world's record" is created and used: Bush states that "technical difficulties of all sorts have been ignored," but that, "also ignored are means as yet unknown which may come any day to accelerate technical progress as violently as did the advent of the thermionic tube." Indeed, anyone who stops to consider the performance consequences of trail following – let alone link-directed pointer chasing – over a microfilm library of near universal scope should quickly come to the conclusion that microfilm is no more appropriate a technology for implementing AWMT's vision than Jules Verne's cannon is an appropriate technology for sending astronauts to the Moon. In both cases the vision may be more significant than the specific technology used to describe it.
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The design of this machine inspired at least half a dozen > machines now being built in America, all known affectionately as "Johniacs." In the same book, the first two paragraphs of a chapter on ACE read as follows: > Automatic Computation at the National Physical Laboratory > One of the most modern digital computers which embodies developments and > improvements in the technique of automatic electronic computing was recently > demonstrated at the National Physical Laboratory, Teddington, where it has > been designed and built by a small team of mathematicians and electronics > research engineers on the staff of the Laboratory, assisted by a number of > production engineers from the English Electric Company, Limited. The > equipment so far erected at the Laboratory is only the pilot model of a much > larger installation which will be known as the Automatic Computing Engine, > but although comparatively small in bulk and containing only about 800 > thermionic valves, as can be judged from Plates XII, XIII and XIV, it is an > extremely rapid and versatile calculating machine. > The basic concepts and abstract principles of computation by a machine were > formulated by Dr. A. M. Turing, F.R.S., in a paper1.
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He was a resourceful, inventive and practical engineer. He patented an enciphering and deciphering machine,GB patent 1605232, 30-5-85 Encyphering and Decyphering Machines assigned to the Ministry of Supply with no financial benefit to himself; and he had so many ideas for civilian projects which could not be exploited within the service that he resigned his commission in 1947 in order to set up as a consulting engineer. Partly as a result of his wartime contacts, his company, Henn-Collins Associates, undertook a wide range of projects for government agencies and commercial organisations worldwide, mostly in the field of telecommunications,GB patent GB846895, 29-6-65 Electronic indicator system more particularly for use in mines but he had other interests as well, and in the 1950s and 60s he patented a number of devices of an electro-mechanical nature.US patent 2900848, 25-8-59 Mechanical selective positioning mechanismGB Patent GB807672, 25-8-59 Selective positioning mechanismsGB patent 778408, 10-7-57 Improvements in and relating to mechanical selective positioning mechanisms In his workshop he developed his idea for a quartz crystal clock which by using transistors in place of thermionic valves, made possible a much smaller quartz clock than was previously feasible.
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