A high gain photonic band gap gyrotron amplifier

A gyrotron amplifier that uses a novel photonic band gap (PBG) interaction circuit has achieved a peak small signal gain of 38 dB at 247.7 GHz, 32 kV and 0.35 A. The instantaneous -3 dB bandwidth of the amplifier at peak gain is 0.4 GHz. A peak output power of 45 W has been measured. The output power is not saturated but is limited by the 7.5 mW of available input power; the saturated output power is believed to be of order 500W. The PBG interaction circuit that confines the TE03-like mode for operation and provides stability from oscillations in lower order modes. The amplifier can be tuned for operation from 245-255 GHz. Experimental results taken over a wide range of parameters, 15-30 kV and 0.25-0.5 A, show good agreement with a theoretical model that incorporates cold test measurements for the transmission line, input coupler, PBG waveguide and mode converter.