Enhancement of cavity selectivity in relativistic gyrotrons operated at axisymmetric modes

Abstract

Mode selection is a key problem from the viewpoint of maintaining the single-mode generation regime in high-power gyrotrons operated at axisymmetric modes. In this paper, we propose several electrodynamic methods of mode selection, which allow separating the electrically strong axisymmetric higher-order mode from spurious modes. The possibility of suppressing the nearest spurious modes efficiently, by using either wide slits in the cavity, or azimuthal corrugations on the walls of the tapered cavity, is shown. A method of mode selection at cyclotron frequency harmonics is proposed. The results of studying two types of gyrotron cavities experimentally at a low power level confirmed their high selective properties. The cavities were calculated aiming at using them as the basis for creation of a gyrotron operated at the TE 0.3 mode and producing a power of 5-10 MW in 1 µs long pulses at a wavelength of 1 cm.

Suppression criteria of parasitic mode oscillations in a gyrotron beam tunnel

“…9,10 The starting current depends inversely on the quality factor and the beam-wave coupling coefficient ͓I st ϰ 1 / ͑Q · C͔͒. 10 In the case of the beam tunnel, I st can be enhanced by decreasing the Q value of the structure ͑the lossy ceramic rings used in beam tunnel reduce the Q value͒ and this methodology is described elsewhere in detail. 11,12,6 In this article, another approach to suppress the a͒ Electronic mail: nitin_physika@rediffmail.com.…”