Design of an efficient, low voltage, third harmonic, large-orbit gyrotron amplifier with a vane-resonator output cavity

Abstract

We present the design of a 100 kW, J-band, third harmonic large-orbit gyrotron amplifier which utilizes the interaction between a 45 kV, 4 A beam and a vane resonator output cavity operating in the "?r"-mode. An efficiency of 55% is predicted with a large signal gain near 20 dB by a single particle code which takes into account nonideal effects associated with finite beam thickness and finite magnetic field transition widths. High efficiency is achieved by velocity modulation of an axially-streaming annular beam via a short TM310 drive cavity. Ballistically created axial bunches are converted into azimuthal bunches when the beam encounters a nonadiabatic, balanced magnetic field reversal at the end of a 30 cm drift region. The design of this tube is presented and its performance is completely characterized before the prospects for the operation of this low voltage configuration at other harmonics are explored.

Mode selection and slow-wave characteristics of groove modes of a magnetron-type cavity

“…However, can decrease with decreasing at sufficiently small q and . As an example, this occurs for the cavities with2 Dissipative rarefaction of the complex natural frequency spectrum for the modes corresponding to the first resonance, r0 s 0.1, r s 1.75, N s 16 1 25 and the same other parameters as in Figure 1, 2 1…”

Studies on a third-harmonic large-orbit gyro-traveling-wave-tube amplifier

“…If the device can operate on a higher cyclotron harmonic number s, then the requisite magnetic field will decrease approximately by a factor of s. As the required frequencies increase, high harmonic operation is an inevitable choice. [2][3][4][5][6] High harmonic interaction is prone to mode selection problems due to the mode competition from the first and lower harmonic interactions. Fortunately, the aforementioned problems can be alleviated to a great extent by using largeorbit ͑axis-encircling͒ electron beams.…”