"microwaves using the interaction of a stream of electrons with a magnetic field. This device, which promised to revolutionize radar, demolished any thoughts the Americans had entertained about their technological leadership. Alfred Lee Loomis of the National Defense Research Committee established the Radiation Laboratory at the Massachusetts Institute of Technology to develop this technology. Ramsey was one of the scientists recruited by Rabi for this work. Initially, Ramsey was in Rabi's magnetron group. When Rabi became a division head, Ramsey became the group leader. The role of the group was to develop the magnetron to permit a reduction in wavelength"
"as a low-cost microwave source for microwave ovens. In this form, approximately one billion magnetrons are in use today. In a conventional electron tube (vacuum tube), electrons are emitted from a negatively charged, heated component called the cathode and are attracted to a positively charged component called the anode. The components are normally arranged concentrically, placed within a tubular-shaped container from which all air has been evacuated, so that the electrons can move freely (hence the name ""vacuum"" tubes, called ""valves"" by the British) If a third electrode is inserted between the cathode and the anode (called a control grid),"
"Micropup In electronics, a micropup is a style of triode vacuum tube (valve) developed during World War II for use at very high frequencies such as those used in radar. They are characterized by an external anode block, which allows better heat dissipation. These tubes could deliver radio frequency power on the order of kilowatts at wavelengths as short as 25 cm., and on the order of 100 kW at 200 MHZ in pulses. Micropup tubes used very high voltages to minimize the transit time of electrons between anode and cathode. The development of the micropup vacuum tube was made"
"Micropup In electronics, a micropup is a style of triode vacuum tube (valve) developed during World War II for use at very high frequencies such as those used in radar. They are characterized by an external anode block, which allows better heat dissipation. These tubes could deliver radio frequency power on the order of kilowatts at wavelengths as short as 25 cm., and on the order of 100 kW at 200 MHZ in pulses. Micropup tubes used very high voltages to minimize the transit time of electrons between anode and cathode. The development of the micropup vacuum tube was made"
"in field emission display technology, but there were significant production problems. As of 2014, NASA's Ames Research Center was reported on working on vacuum-channel transistors produced using CMOS techniques. Vacuum tube In electronics, a vacuum tube, an electron tube, or valve (British usage) or, colloquially, a tube (North America), 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 heated cathode and is used for a number"
"in a cylindrical vacuum chamber within a transverse magnetic field is also employed in the magnetron, a device for producing high frequency radio waves (microwaves). The synchrotron moves the particles through a path of constant radius, allowing it to be made as a pipe and so of much larger radius than is practical with the cyclotron and synchrocyclotron. The larger radius allows the use of numerous magnets, each of which imparts angular momentum and so allows particles of higher velocity (mass) to be kept within the bounds of the evacuated pipe. The magnetic field strength of each of the bending"
"Gyrotron A gyrotron is a class of high-power linear-beam vacuum tubes which generates millimeter-wave electromagnetic waves by the cyclotron resonance of electrons in a strong magnetic field. Output frequencies range from about 20 to 527 GHz, covering wavelengths from microwave to the edge of the terahertz gap. Typical output powers range from tens of kilowatts to 1–2 megawatts. Gyrotrons can be designed for pulsed or continuous operation. The gyrotron is a type of free-electron maser which generates high-frequency electromagnetic radiation by stimulated cyclotron resonance of electrons moving through a strong magnetic field. It can produce high power at millimeter wavelengths"
"Vacuum tube In electronics, a vacuum tube, an electron tube, or valve (British usage) or, colloquially, a tube (North America), 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 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"
"been renewed interest in vacuum tubes, this time with the electron emitter formed on a flat silicon substrate, as in integrated circuit technology. This subject is now called vacuum nanoelectronics. The most common design uses a cold cathode in the form of a large-area field electron source (for example a field emitter array). With these devices, electrons are field-emitted from a large number of closely spaced individual emission sites. Such integrated microtubes may find application in microwave devices including mobile phones, for Bluetooth and Wi-Fi transmission, and in radar and satellite communication. , they were being studied for possible applications"
"make a magnetic bottle to confine the ion reactions. A brief description of the device, being a hydrogen tube wrapped with high voltage coils and a sort of energizing coil being similar to a high voltage tesla coil for the ionizer. The device having been made in a clear glass tube in early experiments uses induction to ionize the gases and the field made by ionized gases to energize ion tube coils. The effect is similar to pyroelectric fusion but instead of pyroelectric crystals stripping the electrons from hydrogen atoms it is a high voltage induced electromagnetic field of coils"
"Backward-wave oscillator A backward wave oscillator (BWO), also called carcinotron (a trade name for tubes manufactured by CSF, now Thales) or backward wave tube, is a vacuum tube that is used to generate microwaves up to the terahertz range. It belongs to the traveling-wave tube family. It is an oscillator with a wide electronic tuning range. An electron gun generates an electron beam that is interacting with a slow-wave structure. It sustains the oscillations by propagating a traveling wave backwards against the beam. The generated electromagnetic wave power has its group velocity directed oppositely to the direction of motion of"
"inside the ""central tube"" towards the exhaust nozzle. These particles could for example be nitrogen- or hydrogen molecules, as well as noble gases like argon or xenon. Since the particles are ionized, they react on the two magnetic fields, which are generated by the ""primary and the secondary coil"". Of these two, the primary coil is permanently switched on as it also forms the magnetic exhaust nozzle, while the secondary coil is cyclically switched on and off to deform the magnetic field lines of the system. By this deformation Alfvén Waves are generated, which – in the next step –"
"placed it inside a glass enclosure evacuated with an external vacuum pump, and placed the entire assembly between the poles of a powerful horseshoe magnet, which caused the electrons to bend around into a circular path. Trying it out for the first time on 21 February 1940, it immediately began producing 400 W of 10 cm (3 GHz) microwaves. Within days they noticed that it was causing fluorescent tubes to light up across the room. Quick calculations showed this meant the tube was creating about 500 W, already beating the klystrons. They pushed this over 1,000 W within weeks. The"
"automotive waste, coal, oil shale, and oil sands into natural gas and diesel fuel. Klystron A klystron is a specialized linear-beam vacuum tube, invented in 1937 by American electrical engineers Russell and Sigurd Varian, which is used as an amplifier for high radio frequencies, from UHF up into the microwave range. Low-power klystrons are used as oscillators in terrestrial microwave relay communications links, while high-power klystrons are used as output tubes in UHF television transmitters, satellite communication, radar transmitters, and to generate the drive power for modern particle accelerators. In a klystron, an electron beam interacts with radio waves as"
"a window in the side of the tube into a waveguide. The spent electron beam is absorbed by a collector electrode at the end of the tube. As in other linear-beam microwave tubes, the energy of the output electromagnetic waves comes from the kinetic energy of the electron beam, which is due to the accelerating anode voltage. In the region before the resonant cavity where the magnetic field strength is increasing, it compresses the electron beam, converting the longitudinal drift velocity to transverse orbital velocity, in a process similar to that occurring in a magnetic mirror used in plasma confinement."
"in microwave tubes ""increases"" capacitances, but this increase is offset by their overall reduced dimensions compared to lower-frequency tubes. 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 a few 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. The negative electrons are attracted to the positively charged"
"in the range of hundred or more kilovolts and duration of about 50-150 nanoseconds. The electrons are attracted to a thin anode, such as an aluminized PET film or a stainless steel mesh, that is connected to the grounded waveguide body. The unit is surrounded by a magnet. Due to the intensity of the electron beam, many electrons pass through the anode into the region beyond it, forming a virtual cathode. The electron beam must be so intense as to exceed the space charge limiting current in that region, causing oscillations that generate microwaves. The frequency, efficiency and other characteristics"
"wire (electromagnets). These are used in cathode ray tubes, found in televisions and computer monitors, and in electron microscopes. After the 1654 invention of the vacuum pump by Otto von Guericke, physicists began to experiment with passing high voltage electricity through rarefied air. In 1705, it was noted that electrostatic generator sparks travel a longer distance through low pressure air than through atmospheric pressure air. In 1838, Michael Faraday applied a high voltage between two metal electrodes at either end of a glass tube that had been partially evacuated of air, and noticed a strange light arc with its beginning"
"also be ionized using a small oven to achieve a vapor phase. The vapor is maintained within a magnetic field long enough for the atoms to be ionized by collisions with electrons. Microwaves are applied to the chamber as to keep the electrons in motion. The vapor is introduced via injection directly into the “magnetic bottle” or the magnetic field. Circular coils provide the shape for the magnetic bottle. The coils are found at the top and bottom of the chamber with a hexapole magnet around the sides. A hexapole magnet consists of permanent magnets or superconducting coils. The plasma"
"electrons as the later electronic vacuum tubes usually do. Instead, electrons are generated by the ionization of the residual air by a high DC voltage (from a few kilovolts to about 100 kilovolts) applied between the cathode and anode electrodes in the tube, usually by an induction coil (a ""Ruhmkorff coil""). The Crookes tubes require a small amount of air in them to function, from about 10 to 5×10 atmosphere (7×10 - 4×10 torr or 0.1-0.005 pascal). When high voltage is applied to the tube, the electric field accelerates the small number of electrically charged ions and free electrons always"
"several smaller facilities located in and outside Moscow that produce medical equipment, vacuum pumps, and vacuum tube components. NPO Toriy Toriy Scientific Production Association () is a company based in Moscow, Russia. It is part of Ruselectronics. The Toriy Scientific Production Association produces microwave tubes for use in radars, communications systems, television broadcasting electron accelerators (pulsed amplifiers), and nuclear reactors systems (gyrotrons) as well as medical equipment, and consumer goods. The association also produces linear accelerators, and claims to be the world's only producer of new high voltage vacuum control tubes (Titrons) for use in electron-beam welding installations and computer-based"
"injected microwaves' frequency is set to match this gyrofrequency and a resonance is established. Energy is transferred from the right-hand polarized portion of the microwave to the electrons. This energy is then transferred to the bulk gas/plasma via the rare - yet important - collisions between electrons and neutrals. During these collisions, electrons can be knocked free from the neutrals, forming ion-electron pairs. The process is a highly efficient means of creating a plasma in low density gases. Previously the electrons required were provided by a hollow cathode. The thruster itself is in the 20-50 kW class, with a specific"
"the prototype design) is coupled into a specially shaped antenna wrapped around the chamber. The electromagnetic wave emitted by the antenna causes the gas to break down and form a plasma. The antenna then excites a helicon wave in the plasma, which further heats the plasma. The device has a roughly constant magnetic field in the source tube (supplied by solenoids in the prototype), but the magnetic field diverges and rapidly decreases in magnitude away from the source region, and might be thought of as a kind of magnetic nozzle. In operation, there is a sharp boundary between the high"
"elongated vacuum tube with an electron gun (a heated cathode that emits electrons) at one end. A voltage applied across the cathode and anode accelerates the electrons towards the far end of the tube, and an external magnetic field around the tube focuses the electrons into a beam. At the other end of the tube the electrons strike the ""collector"", which returns them to the circuit. Wrapped around the inside of the tube, just outside the beam path, is a helix of wire, typically oxygen-free copper. The RF signal to be amplified is fed into the helix at a point"
"Traveling-wave tube A traveling-wave tube (TWT, pronounced ""twit"") or traveling-wave tube amplifier (TWTA, pronounced ""tweeta"") is a specialized vacuum tube that is used in electronics to amplify radio frequency (RF) signals in the microwave range. The TWT belongs to a category of ""linear beam"" tubes, such as the klystron, in which the radio wave is amplified by absorbing power from a beam of electrons as it passes down the tube. Although there are various types of TWT, two major categories are: A major advantage of the TWT over some other microwave tubes is its ability to amplify a wide range"
"important for certain types of vacuum tubes and for high-voltage vacuum switches. The thermionic vacuum arc (TVA) is a new type of plasma source, which generates a plasma containing ions with a directed energy. TVA discharges can be ignited in high-vacuum conditions between a heated cathode (electron gun) and an anode (tungsten crucible) containing the material. The accelerated electron beam, incident on the anode, heats the crucible, together with its contents, to a high temperature. After establishing a steady-state density of the evaporating anode material atoms, and when the voltage applied is high enough, a bright discharge is ignited between"
"wave tube (TWT) developed in 1943 by Rudolph Kompfner and John Pierce provided a high-power tunable source of microwaves up to 50 GHz, and became the most widely used microwave tube (besides the ubiquitous magnetron used in microwave ovens). The gyrotron tube family developed in Russia could produce megawatts of power up into millimeter wave frequencies, and is used in industrial heating and plasma research, and to power particle accelerators and nuclear fusion reactors. The development of semiconductor electronics in the 1950s led to the first solid state microwave devices which worked by a new principle; negative resistance (some of"
"residual gas atoms in the tube. The positive ions were accelerated by the electric field toward the cathode, and when they collided with it they knocked electrons out if its surface; these were the cathode rays. Modern vacuum tubes use thermionic emission, in which the cathode is made of a thin wire filament which is heated by a separate electric current passing through it. The increased random heat motion of the filament knocks electrons out of the surface of the filament, into the evacuated space of the tube. Since the electrons have a negative charge, they are repelled by the"
"on the voltage on the grid. Thus, a small voltage on the grid can be made to control a much larger voltage on the anode. This is the principle used in vacuum tubes to amplify electrical signals. The triode vacuum tube developed between 1907 and 1914 was the first electronic device that could amplify, and is still used in some applications such as radio transmitters. High speed beams of cathode rays can also be steered and manipulated by electric fields created by additional metal plates in the tube to which voltage is applied, or magnetic fields created by coils of"
"true electronic vacuum tubes, invented in 1904 by John Ambrose Fleming, used this hot cathode technique, and they superseded Crookes tubes. These tubes didn't need gas in them to work, so they were evacuated to a lower pressure, around 10 atm (10 Pa). The ionization method of creating cathode rays used in Crookes tubes is today only used in a few specialized gas discharge tubes such as krytrons. In 1906, Lee De Forest found that a small voltage on a grid of metal wires could control a much larger current in a beam of cathode rays passing through a vacuum"
"The electromagnetic wave emitted by the antenna causes the gas to break down and form a plasma. The antenna then excites a helicon wave in the plasma, which further heats it. The device has a roughly constant magnetic field in the source tube (supplied by solenoids in the prototype), but the magnetic field diverges and rapidly decreases in magnitude away from the source region and might be thought of as a kind of magnetic nozzle. In operation, a sharp boundary separates the high density plasma inside the source region and the low density plasma in the exhaust, which is associated"
"resonant cavity structure in a strong axial magnetic field, usually created by a superconducting magnet around the tube. The field causes the electrons to move helically in tight circles around the magnetic field lines as they travel lengthwise through the tube. At the position in the tube where the magnetic field reaches its maximum the electrons radiate electromagnetic waves in a transverse direction (perpendicular to the axis of the tube) at their cyclotron resonance frequency. The millimeter radiation forms standing waves in the tube, which acts as an open-ended resonant cavity, and is formed into a beam, which radiates through"
"provides the microwave field that is passed through a waveguide to the lighting cavity containing the light-emitting substance (e.g., sulfur, metal halides, etc.). Although efficient, these lamps are much more complex than other methods of lighting and therefore not commonly used. More modern variants use HEMTs or GaN-on-SiC power semiconductors to generate the microwaves, which are substantially less complex and can be adjusted to maximize light output using a PID system. In 1910 Hans Gerdien of the Siemens corporation invented a magnetron. In 1912, Swiss physicist Heinrich Greinacher was looking for new ways to calculate the electron mass. He settled"