Effects of tapered magnetic fields and structures on long-pulse gyrotron backward-wave oscillator performance

摘要

Abstract: Results are presented of microwave spectral measurements on a gyrotron-backward-wave- oscillator (gyro-BWO) driven by a long-pulse, relativistic electron beam. The Michigan Electron Long Beam Accelerator (MELBA) generates 800 kV, 1-4 kA, 0.5 $mu@s electron beams from a cold cathode. Gyro-BWO microwave emission has shown high-power fundamental-cyclotron (4.5-5 GHz) emission (peak of approximately 40-50 MW tube power). Second cyclotron-harmonic gyro-BWO microwave emission spectra are reported here in the frequency range from 5-6 GHz, at lower tube powers (MW range). The effects of tapered magnetic fields with uniform or tapered interaction radii are to broaden the microwave spectrum over the uniform tube-field case. !13