DESIGN OF A 50 KW, WIDE-BAND KA-BAND SLOW-WAVE CYCLOTRON AMPLIFIER

A two stage slow wave cyclotron amplifier is investigated to demonstrate a high power, stable, and broad Ka-band radiation source, operating at a low beam power (similar to 60 kV, similar to 5 amps) and a low magnetic field (similar to 7 kG) A linear theory predicts that the second harmonic gyro-BWO is competing in the amplifier and can be stabilized by inserting a sever in the interaction circuit. A slow-time-scale non-linear code, with a sever included, predicts a saturated gain of 24-28 dB, an efficiency of 15-17%, and an instantaneous bandwidth of 15-20% at a beam axial velocity spread of 2%. A broadband rf coupler, a mode converter, and a rf vacuum window are designed by the use of a 3-D electromagnetic, finite element code. Measured rf characteristics are in good agreement with predictions.