Numerical research on a 4 MW 170 GHz coaxial gyrotron with a double electron beam

Abstract

In this paper, a coaxial gyrotron with a double electron beam is investigated on the ohmic loss, starting current, mode competition, and beam wave interaction. Its beam-wave interaction equation and dependence of the starting current on the static magnetic field and parameter K (the ratio of the current of an electron beam to the total current of a double electron beam) are given. On this basis, a 4 MW 170 GHz coaxial gyrotron with a double electron beam is studied. By the numerical calculation, the influence of K on the starting current is analyzed under a given static magnetic field and at different guiding center radii of the double electron beam. Studies show that the ability of the gyrotron to suppress the mode competition has a relation with the selection of the guiding center radii of the two electron beams. Then, the investigation of a time-dependent multi-mode competition of the gyrotron is performed, which shows that the gyrotron can stably operate in the TE38,18− mode. The results show that by considering the ohmic loss, the gyrotron can operate at 170.4 GHz with the output power of 4.04 MW and the beam-wave interaction efficiency of 35.47% when B = 6.82 T, U = 88 KV, I = 129 A, and K = 0.4. Each of the two electron beams in the gyrotron has different beam-wave interaction efficiencies. Compared to the coaxial gyrotron with one electron beam, the beam-wave interaction efficiency of each electron beam in the coaxial gyrotron with a double electron beam has a different increase.

Transition from fishbone mode to β-induced Alfvén eigenmode on HL-2A tokamak

“…The Alfvén continua are needed to identify the radial position and frequency of BAE. By solving the ideal MHD eigenmode equations in a torus, AWEAC (Alfvén Wave Eigen-Analysis Code) can output the Alfvén continuum for the EFIT equilibrium [36]. Based on the Alfvén continua for toroidal mode number n=1 calculated using the AWEAC code, the radial locations and frequencies of the modes with q 0 =0.9 and q 0 =1.05 are well within the BAE gap (figure 13).…”

Design of master oscillator for frequency locking of a complex of megawatt level microwave sources

“…4 Gyrotron complexes have been used successfully for microwave plasma heating for quite a long time in nearly all CF facilities, both in Russia and abroad. 5 However, as the power of gyrotrons increases (the increase in the gyrotron power up to 2 MW and higher being of essential interest [6][7][8][9] or the radiation wavelength shortens, transverse dimensions of the interaction space must satisfy to acceptable level of thermal load on the cavity wall. In such case, the order of operating mode grows up and the spectrum density of potentially excited modes within the cyclotron resonance band increases.…”