CW operation of a 140  GHz gyrotron†

Single-mode operation of a high-power, step-tunable gyrotron

“…Important advances have been reported in research on electron cyclotron masers such as the gyrotron, ' 4 Cerenkov sources,' free electron lasers," and other novel devices.' For application to plasma heating at millimeter wavelengths, which requires CW or long pulse operation, the gyrotron has achieved the most impressive results, with 100 kW, CW operation at 140 GHz 4 and 200 kW, CW at 60 GHz.10…”

Tilted Resonator Experiments on a Quasioptical Gyrotron.

“…There is some evidence of this in cavity gyrotrons, where beam ';agnostic experiments are being performed on similar electron guns. 3 Finally, it is possible that the electron beam is driving oscillations in the beam transport system before reaching the resonator, bunching the beam and adding a large energy spread. 2 Attempts have been made to measure radiation leaking out of the system through the bottom of the electron gun, but no power has been observed.…”

“…The tilt should be enough to ensure that all electrons in the beam pass through at least one peak of the standing wave, and is predicted to both enhance the interaction efficiency and to greatly increase the parameter range of stable, single-mode operation.' 3 This approach has been tested experimentally and is the subject of this paper.…”

“…For example, the Compact Ignition Tokamak (CIT) design 1 includes 30 MW of 280 GHz radiation and the International Thermonuclear Experimental Reactor (ITER) design 2 requires 20 MW of 140 GHz rf power. The leading candidate for such a source is the waveguide cavity gyrotLoui, 3 having produced an output power of 940 kW at an efficiency of 35% and a frequency of 140 GHz,' and 1.2 MW at an efficiency of 20% at 148 GHz' in a continuous-wave (CW) relevant COnfin,,ra)t"n Howc ,-A, s the frequency and power are increased, these gyrotrons are forced to use more highly overmoded cavities, larger collectors, and vacuum output windows capable of handling the higher powers. The quasioptical gyrotron 6 (QOG) is a reasonable alternative to the cavity gyrotrons that offers several advantages.…”