Study of a high-order-mode gyrotron traveling-wave amplifier

Abstract

Physics and performance issues of a TE01-mode gyrotron traveling-wave amplifier are studied in theory. For a high order mode, absolute instabilities on neighboring modes at the fundamental and higher cyclotron harmonic frequencies impose severe constraints to the device capability. Methods for their stabilization are outlined, on the basis of which the performance characteristics are examined in a multidimensional parameter space under the marginal stability criterion. The results demonstrate the viability of a high-order-mode traveling-wave amplifier and provide a roadmap for design tradeoffs among power, bandwidth, and efficiency. General trends are observed and illustrated with specific examples.

Low-order-mode harmonic multiplying gyrotron traveling-wave amplifier in W band

“…For high-order-mode harmonic multiplying gyro-TWAs, the performance is much more severely constrained by the low-order-mode absolute instabilities. 15,16 To avoid the fundamental harmonic absolute instabilities in the harmonic interaction stage, this work proposes a W-band harmonic multiplying gyro-TWA operating at low-order modes. The second harmonic component (s ¼ 2) of the beam current generates a TE 21 wave by amplifying a TE 11 (s ¼ 1) drive wave.…”

“…This result has been found in previous studies. 16,18 For q 4 > 2:0 Â 10 4 q cu , the field of TE ð3Þ 31 mode is contracted in the copper section L 5 resulting in the weak variations of the start-oscillation current [ Fig. 5(a)].…”

“…This result has been found in previous studies. 16,18 Spurious oscillations must be suppressed to ensure the stable operation of a harmonic multiplying gyro-TWA. The proposed gyro-TWA is most susceptible to the TE Fig.…”

“…However, the additional degree of freedom provided by the multitude of cyclotron harmonics in the high-order-mode gyro-TWA also generates several spurious oscillations. 15,16 This work proposes a W-band harmonic multiplying gyro-TWA operating at loworder modes to avoid the fundamental harmonic absolute instabilities. By amplifying a TE 11 (s ¼ 1) drive wave, the second harmonic component (s ¼ 2) of the beam current initiates a TE 21 wave to be amplified.…”