Gyrotron

The gyrotron ( short form of Gyromonotron ) is currently (2007) powerful microwave oscillator. It is based on the principle of electron cyclotron maser instability and is a combination of drift tube and cyclotron maser. Gyrotron work effectively in the frequency range of 5 GHz to 170 GHz with output powers up to several megawatts. When operating on a harmonic microwaves can be generated in the watt range up to one terahertz. There are conventional gyrotron Koaxialgyrotrons and tunable gyrotron.

They are used, for example, at 30 GHz in the material process technology for sintering ceramics, at 95 GHz in the Active Denial System, or at 100 GHz - 140 GHz (in the range of Elektronzyklotronfrequenz, therefore, electron cyclotron resonance heating ( ECRH ) ) and services to 1 megawatt of microwave heating of plasmas in nuclear fusion reactors (eg at the Max Planck Institute for Plasma Physics or in TCV).

Construction

A gyrotron consists of an electron gun ( Gun), an electron - compression zone, an interaction space ( microwave cavity resonator ), a quasi- optical wave- type converter, an electron collector (collector), a high-frequency output window, the tube housing and magnets.

Function

In a gyrotron electron beam relativistic velocity is first created. At the same time, the electrons pass through there already a magnetic field. The electrons move within the beam on helical paths. The electron beam enters the cavity resonator, which is located in an axial magnetic field. It interacts there due to the cyclotron resonance with a recycled part of the microwave power generated. Now the relativistic mass increase comes into play: Depending on the phase at which the electrons are localized on their helical path relative to the alternating electric field, they are partly accelerated to this, partly slowed down; ( ie faster ) with a larger radius orbiting electrons experience a slowdown due to the mass increase their axial velocity, they will be collected by the lower radius ( slower) orbiting electrons and leads to a phase synchronization. Now the electrons can continuously transfer energy to the alternating electric field of the microwave later in the resonator. The microwaves go out through a window from the vacuum apparatus, while the processed electrons are collected on a positively charged metallic wall (pipe ).

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