Abstract
The last decade has contributed to the rapid progress in the gyrotron development. Megawatt-class, continuous wave gyrotrons are employed as high-power millimeter (mm)-wave sources for electron cyclotron heating (ECH) and current drive in the tokamaks and stellarators. The progress in gyrotron development pushes ECH from a minor to a major heating method. Also gyrotron based technological complexes successfully applied in electron cyclotron resonance ion sources, for microwave ceramic sintering and diamond disk production. The paper describes the main features of high frequency gyrotrons. Some data about pulsed and CW tubes, working in the terahertz frequency range, are given. These gyrotrons operate (in some specific combinations) at very low voltage and beam current, demonstrate an extremely narrow frequency spectrum or wide frequency tuning. Although in comparison with the classical microwave tubes the gyrotrons are characterized by greater volume and weight due to the presence of bulky parts (such as superconducting magnets and massive collectors where the energy of the spent electron beam is dissipated) they can easily be embedded in a sophisticated laboratory equipment (e.g., spectrometers, technological systems, etc.). All these advantageous features have opened the road to many novel and prospective applications of gyrotrons.
Highlights
This review aims to bring together information about the development and the application examples of gyrotrons at IAP RAS1
Gyrotrons [1], [2] are a variety of cyclotron resonance masers (CRMs) which employ resonance interaction of electrons moving along helical trajectories in a magnetostatic field with fast waves propagating across the direction of the magnetic field
At IAP RAS, the development of the terahertz band by the methods of vacuum electronics, as well as by using conventional gyrodevices, which employ extremely strong magnetic fields at the main cyclotron resonance and the second cyclotron harmonic, is supported by the development of gyrodevices operated at higher cyclotron harmonics (large-orbit gyrotrons (LOGs) and gyroamplifiers) and orotrons
Summary
This review aims to bring together information about the development and the application examples of gyrotrons at IAP RAS1. At IAP RAS, the development of the terahertz band by the methods of vacuum electronics, as well as by using conventional gyrodevices, which employ extremely strong magnetic fields at the main cyclotron resonance and the second cyclotron harmonic, is supported by the development of gyrodevices operated at higher cyclotron harmonics (large-orbit gyrotrons (LOGs) and gyroamplifiers) and orotrons (generators, whose operation is based on the stimulated Smith-Purcell radiation of rectilinear electron beams in an open cavity). Wide step tuning of the frequency by excitation of various modes was demonstrated in the range of 0.4-0.78 THz. Stable operation at the frequency of 0.78 THz at the second harmonic with a power level of about few Watts has been obtained, which is useful for modern NMR/DNP spectroscopy applications. An output power of 0.5 to 1 kW can be obtained at a frequency of about 0.2 THz within a 10 GHz band, which are the parameters needed for testing of quantum electrodynamics predictions in positronium spectroscopy measurements
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