Terahertz Gyrotrons at IAP RAS: Status and New Designs

Abstract

Powerful gyrotrons with radiation frequencies in the range 0.33-0.65 THz were demonstrated at the IAP as early as in the 1970-1980s. This trend has recently been renewed in connection with a significant increase in interest in terahertz frequency range. In the course of new experiments, the radiation frequency of pulsed gyrotrons was increased up to 1.3 THz and 1 THz at the fundamental and third cyclotron harmonics, respectively. In addition, gyrotrons operated in CW regime with a frequency of 0.3 THz for technological applications (in collaboration with the University of Fukui, Japan) and 0.26 THz for the dynamic nuclear polarization at a high-field NMR were implemented. Designs of a pulsed fundamental-harmonic gyrotron with MW-level power at 0.3 THz and a CW kW-level third-harmonic gyrotron with a frequency of 0.4 THz are currently developed. Estimates show that modern techniques for the creation of strong magnetic fields now make it possible to realize gyrotrons with an operating frequency at least up to 1-1.5 THz. Such generators utilize a relatively low particle energy and can provide higher average power than the existing FELs.

Operation of a Continuously Frequency-Tunable Second-Harmonic CW 330-GHz Gyrotron for Dynamic Nuclear Polarization

“…YROTRON oscillators are vacuum electron devices that have delivered MW power levels at millimeter wavelengths [1], and kW power levels in the THz or submillimeter band [2], [3]. The lack of other sources able to match these power levels in the abovementioned bands, with the exception of much bulkier free electron lasers, makes the gyrotron the oscillator of choice in many applications such as plasma heating [1], materials processing [4], diagnostics [5], spectroscopy [6], and in non-lethal weapons [7].…”

Two-wave regime of operation of the high-harmonic gyrotron

“…The use of the high-harmonic operation is a natural way of decreasing magnetic fields in gyrotrons and increasing their frequency to the THz frequency range. [5][6][7][8][9][10][11][12][13][14][15] Naturally, realization of a high-harmonic gyrotron demands the problem of selectivity to be solved, which becomes more severe because of large number of competing oscillations at lower cyclotron harmonics. In practice, in a conventional scheme of a gyrotron driven by a hollow electron beam formed by a magnetron injection gun, one manages to realize the operation in the THz range at the second cyclotron harmonic at best.…”

“…In practice, in a conventional scheme of a gyrotron driven by a hollow electron beam formed by a magnetron injection gun, one manages to realize the operation in the THz range at the second cyclotron harmonic at best. A more selective scheme of a large orbit gyrotron (LOG) 5,[11][12][13][14][15] allows increasing the operating cyclotron harmonic number up to third or fourth. However, this is accompanied by dramatic increase of Ohmic losses due to a large length of gyrotron cavity, which is necessary to compensate the weakening of the electron-wave coupling at the high cyclotron harmonic.…”

Plasma glow dynamics of pulsed nitrogen discharge induced by the powerful terahertz waves

“…n recent years, high-power pulse gyrotrons operated in the terahertz frequency range have been developed [1,2], which allowed one to start studying discharge phenomena in quasioptical beams of terahertz waves. The dense plasma produced by a terahertz wave beam is a new, poorly studied subject of gas-discharge physics, therefore, this research line is of fundamental interest.…”