High-power 140 GHz gyrotron for plasma heating in the fusion experiment, Germany.">Wendelstein 7-X fusion experiment, Germany.
A gyrotron is a class of high-power linear-beam
vacuum tube
A vacuum tube, electron tube, thermionic valve (British usage), or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. It ...
s that generates
millimeter-wave
Extremely high frequency (EHF) is the International Telecommunication Union designation for the band of radio frequencies in the electromagnetic spectrum from 30 to 300 gigahertz (GHz). It is in the microwave part of the radio spectrum, between t ...
electromagnetic waves by the
cyclotron resonance Cyclotron resonance may refer to:
* Cyclotron motion - the motion of charged particles in a magnetic field
* Ion cyclotron resonance - the motion of heavy ions in a magnetic field
* Electron cyclotron resonance
Electron cyclotron resonance (ECR) ...
of
electron
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
s in a strong
magnetic field
A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...
. Output
frequencies
Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...
range from about 20 to 527
GHz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in ter ...
,
covering wavelengths from
microwave
Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...
to the edge of the
terahertz gap
Terahertz radiation – also known as submillimeter radiation, terahertz waves, tremendously high frequency
(THF), T-rays, T-waves, T-light, T-lux or THz – consists of electromagnetic waves within the International Telecommunicat ...
. Typical output
power
Power may refer to:
Common meanings
* Power (physics), meaning "rate of doing work"
** Engine power, the power put out by an engine
** Electric power, a type of energy
* Power (social and political), the ability to influence people or events
Math ...
s range from tens of
kilowatt
The watt (symbol: W) is the unit of Power (physics), power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantification (science), quantify the rate of Work ...
s to 1–2
megawatt
The watt (symbol: W) is the unit of Power (physics), power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantification (science), quantify the rate of Work ...
s. Gyrotrons can be designed for pulsed or continuous operation. The gyrotron was invented by
Soviet scientists
Polymaths
*Karl Ernst von Baer, polymath naturalist, formulated the geological Baer's law on river erosion and embryological Baer's laws, founder of the Russian Entomological Society, co-founder of the Russian Geographical Society
*Alexander Boro ...
at
NIRFI
The Radiophysical Research Institute (NIRFI), based in Nizhny Novgorod, Russia, is a research institute that conducts basic and applied research in the field of radiophysics, radio astronomy, cosmology and radio engineering. It is also known for ...
, based in
Nizhny Novgorod
Nizhny Novgorod ( ; rus, links=no, Нижний Новгород, a=Ru-Nizhny Novgorod.ogg, p=ˈnʲiʐnʲɪj ˈnovɡərət, t=Lower Newtown; colloquially shortened to Nizhny) is a city and the administrative centre of Nizhny Novgorod Oblast an ...
,
Russia
Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...
.
Principle
The gyrotron is a type of free-electron
maser
A maser is a device that produces coherent electromagnetic waves ( microwaves), through amplification by stimulated emission. The term is an acronym for microwave amplification by stimulated emission of radiation. Nikolay Basov, Alexander Pr ...
that 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 because, as a ''fast-wave'' device, its dimensions can be much larger than the wavelength of the radiation. This is unlike conventional microwave
vacuum tube
A vacuum tube, electron tube, thermionic valve (British usage), or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. It ...
s such as
klystron
A klystron is a specialized linear-beam vacuum tube, invented in 1937 by American electrical engineers Russell and Sigurd Varian,Pond, Norman H. "The Tube Guys". Russ Cochran, 2008 p.31-40 which is used as an amplifier for high radio frequenci ...
s and
magnetron
The cavity magnetron is a high-power vacuum tube used in early radar systems and subsequently in microwave oven, microwave ovens and in linear particle accelerators. A cavity magnetron generates microwaves using the interaction of a stream of ...
s, in which the wavelength is determined by a single-mode
resonant cavity
A resonator is a device or system that exhibits resonance or resonant behavior. That is, it naturally oscillates with greater amplitude at some frequencies, called resonant frequencies, than at other frequencies. The oscillations in a resona ...
, a ''slow-wave'' structure. Thus, as operating frequencies increase, the resonant cavity structures must decrease in size, which limits their power-handling capability.
A gyrotron (right) in cross-section (left). The electron path is shown in blue, and the generated microwave radiation is in pink.
In the gyrotron, a hot
filament
The word filament, which is descended from Latin ''filum'' meaning " thread", is used in English for a variety of thread-like structures, including:
Astronomy
* Galaxy filament, the largest known cosmic structures in the universe
* Solar filament ...
in an
electron gun
file:Egun.jpg, Electron gun from a cathode-ray tube
file:Vidicon Electron Gun.jpg, The electron gun from an RCA Vidicon video camera tube
An electron gun (also called electron emitter) is an electrical component in some vacuum tubes that produc ...
(1) at one end of the tube emits an annular-shaped (hollow tubular) beam of
electron
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
s (6), which is accelerated by a high-voltage
DC anode
An anode usually is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, which is usually an electrode of the device through which conventional current leaves the devic ...
(10) and then travels through a large tubular resonant cavity structure (2) in a strong axial
magnetic field
A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...
, usually created by a
superconducting magnet
A superconducting magnet is an electromagnet made from coils of superconducting wire. They must be cooled to cryogenic temperatures during operation. In its superconducting state the wire has no electrical resistance and therefore can conduct much ...
around the tube (8). 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 (2), the electrons radiate electromagnetic waves, parallel to the axis of the tube, at their cyclotron resonance frequency. The millimeter radiation forms
standing waves
In physics, a standing wave, also known as a stationary wave, is a wave that oscillates in time but whose peak amplitude profile does not move in space. The peak amplitude of the wave oscillations at any point in space is constant with respect t ...
in the tube, which acts as an open-ended
resonant cavity
A resonator is a device or system that exhibits resonance or resonant behavior. That is, it naturally oscillates with greater amplitude at some frequencies, called resonant frequencies, than at other frequencies. The oscillations in a resona ...
, and is formed into a beam. The beam is converted by a
mode converter (9) and reflected by mirrors (4), which direct it through a window (5) in the side of the tube into a microwave
waveguide
A waveguide is a structure that guides waves by restricting the transmission of energy to one direction. Common types of waveguides include acoustic waveguides which direct sound, optical waveguides which direct light, and radio-frequency w ...
(7). A collector electrode absorbs the spent electron beam at the end of the tube (3).
As in other linear-beam microwave tubes, the energy of the output electromagnetic waves comes from the
kinetic energy
In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion.
In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2.Resnick, Rober ...
of the electron beam, which is due to the accelerating anode voltage (10). 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
A magnetic mirror, also known as a magnetic trap or sometimes as a pyrotron, is a type of magnetic confinement fusion device used in fusion power to trap high temperature Plasma (physics), plasma using magnetic fields. The mirror was one of the e ...
used in
plasma confinement
In Plasma (physics), plasma physics, plasma confinement refers to the act of maintaining a Plasma (physics), plasma in a discrete volume. Confining plasma is required in order to achieve fusion power. There are two major approaches to confinement: ...
.
The orbital velocity of the electrons is 1.5 to 2 times their axial beam velocity. Due to the standing waves in the resonant cavity, the electrons become "bunched"; that is, their phase becomes
coherent
Coherence is, in general, a state or situation in which all the parts or ideas fit together well so that they form a united whole.
More specifically, coherence, coherency, or coherent may refer to the following:
Physics
* Coherence (physics ...
(synchronized), so they are all at the same point in their orbit at the same time. Therefore, they emit
coherent radiation.
The electron speed in a gyrotron is slightly relativistic (on the order of but not close to the speed of light). This contrasts to the
free-electron laser
A free-electron laser (FEL) is a fourth generation light source producing extremely brilliant and short pulses of radiation. An FEL functions much as a laser but employs relativistic electrons as a active laser medium, gain medium instead of using ...
(and
xaser
An X-ray laser can be created by several methods either in hot, dense plasmas or as a free-electron laser in an accelerator. This article describes the x-ray lasers in plasmas, only.
The plasma x-ray lasers rely on stimulated emission to gener ...
) that work on different principles and whose electrons are highly relativistic.
Applications
Gyrotrons are used for many industrial and high-technology heating applications. For example, gyrotrons are used in
nuclear fusion
Nuclear fusion is a nuclear reaction, reaction in which two or more atomic nuclei combine to form a larger nuclei, nuclei/neutrons, neutron by-products. The difference in mass between the reactants and products is manifested as either the rele ...
research experiments to heat
plasmas and also in the manufacturing industry as a rapid heating tool in processing glass, composites, and ceramics, as well as for annealing (solar and semiconductors). Military applications include the
Active Denial System
The Active Denial System (ADS) is a directed-energy weapon developed by the United States armed forces, U.S. military, designed for area denial, perimeter security and crowd control. Informally, the weapon is also called the heat ray since it wo ...
.
Types
The output window of the tube from which the microwave beam emerges can be in two locations. In the transverse-output gyrotron, the beam exits through a window on the side of the tube. This requires a 45° mirror at the end of the cavity to reflect the microwave beam, positioned at one side so the electron beam misses it. In the axial-output gyrotron, the beam exits through a window at the end of the tube at the far end of the cylindrical collector electrode which collects the electrons.
The original gyrotron developed in 1964 was an oscillator, but since that time gyrotron
amplifier
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power su ...
s have been developed. The helical gyrotron electron beam can amplify an applied microwave signal similarly to the way a straight electron beam amplifies in classical microwave tubes such as the klystron, so there is a series of gyrotrons that function analogously to these tubes. Their advantage is that they can operate at much higher frequencies.
The gyro-monotron (gyro-oscillator) is a single-cavity gyrotron that functions as an oscillator. A gyro-klystron is an amplifier that functions analogously to a
klystron
A klystron is a specialized linear-beam vacuum tube, invented in 1937 by American electrical engineers Russell and Sigurd Varian,Pond, Norman H. "The Tube Guys". Russ Cochran, 2008 p.31-40 which is used as an amplifier for high radio frequenci ...
tube. Has two
microwave cavities along the electron beam, an input cavity upstream to which the signal to be amplified is applied and an output cavity downstream from which the output is taken. A gyro-TWT is an amplifier that functions analogously to a
travelling 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. It was invented ...
(TWT). It has a slow wave structure similar to a TWT paralleling the beam, with the input microwave signal applied to the upstream end and the amplified output signal taken from the downstream end. A gyro-BWO is an oscillator that functions analogously to a
backward wave oscillator
A backward wave oscillator (BWO), also called carcinotron or backward wave tube, is a vacuum tube that is used to generate microwaves up to the Terahertz radiation, terahertz range. Belonging to the traveling-wave tube family, it is an electroni ...
(BWO). It generates oscillations traveling in an opposite direction to the electron beam, which is output at the upstream end of the tube. A gyro-twystron is an amplifier that functions analogously to a
twystron
A twystron is a type of microwave-producing vacuum tube most commonly found in high-power radar systems. The name refers to its construction, which combines a traveling wave tube, or TWT, with a klystron, producing a tw-ystron. The name was origina ...
, a tube that combines a klystron and a TWT. Like a klystron, it has an input cavity at the upstream end followed by buncher cavities to bunch the electrons, which are followed by a TWT-type slow-wave structure that develops the amplified output signal. Like a TWT, it has a wide bandwidth.
Manufacturers
The gyrotron was invented in the
Soviet Union
The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
. Present makers include
Communications & Power Industries
CPI International, Inc. is the holding company for Communications & Power Industries, the largest manufacturer and rebuilder of electron devices (primarily vacuum tubes) in the United States. CPI was founded in 1995 when Varian Associates sold i ...
(USA),
Gycom (Russia),
Thales Group
Thales S.A., Trade name, trading as Thales Group (), is a French multinational corporation, multinational aerospace and defence industry, defence corporation specializing in electronics. It designs, develops and manufactures a wide variety of aer ...
(EU),
Kyoto Fusioneering
Kyoto ( or ; Japanese language, Japanese: , ''Kyōto'' ), officially , is the capital city of Kyoto Prefecture in the Kansai region of Japan's largest and most populous island of Honshu. , the city had a population of 1.46 million, making it t ...
(Japan),
Toshiba
is a Japanese multinational electronics company headquartered in Minato, Tokyo. Its diversified products and services include power, industrial and social infrastructure systems, elevators and escalators, electronic components, semiconductors ...
(Japan, now
Canon, Inc.,
also from Japan), and
Bridge12 Technologies. System developers include
Gyrotron Technology.
See also
*
Electron cyclotron resonance
Electron cyclotron resonance (ECR) is a phenomenon observed in plasma physics, condensed matter physics, and accelerator physics. It happens when the frequency of incident radiation coincides with the natural frequency of rotation of electrons in ...
*
Fusion power
Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices d ...
*
Terahertz radiation
Terahertz radiation – also known as submillimeter radiation, terahertz waves, tremendously high frequency
(THF), T-rays, T-waves, T-light, T-lux or THz – consists of electromagnetic waves within the International Telecommunicat ...
References
External links
Gyrotron*
{{Electronic components
Microwave technology
Terahertz technology
Soviet inventions
Vacuum tubes
Particle accelerators