Design And Test Of A 250 GHz Induction Linac Driven CARM Oscillator Experiment

A Cyclotron Auto Resonance Maser (CARM) oscillator designed for 250 GHz has been built and is undergoing test using the 1 kA 2 MeV induction linac at the Accelerator Research Center (ARC) facility at Lawrence Livermore National Laboratory. The required axial field of 29 kilogauss is produced by a superconducting magnet from UCLA. The microwave circuit incorporates the "TWYSTRON" concept consisting of a single Bragg reflector section followed by a straight pipe amplification section. The Bragg reflector consists of 300 sinusoidal wall ripples with .6 mm period and 45 micron amplitude which can operate as an internal cavity oscillator exiting a TE
₁₁
resonant mode 10 times above cutoff at 250 GHz with an external Q of 5000. Theory predicts overall output powers of over 200 MW with cavity fill times less than 30 ns (pulse length). Initial experimental results indicate that 50 MW of power at frequencies above 180 GHz have been produced.