HIGH-POWER CARM AND HARMONIC GYRO-AMPLIFIER EXPERIMENTS

Cyclotron resonance maser oscillators and amplifiers are attractive so urces for applications such as electron cyclotron resonance heating (E CRH) of fusion plasmas and driving high gradient RF accelerators. For ECRH applications oscillators in the 140-280 GHz range with high avera ge power (> 1 MW) are required. A 27.8 GHz long-pulse (1 mus) CARM osc illator experiment has been carried out at the MIT Plasma Fusion Cente r. A 450 keV, 80 A electron beam is generated by a diode Pierce gun. T he interaction takes place inside a Bragg resonator. Output power of 1 .9 MW (efficiency of 5.2%) has been measured in the TE11 mode. A signi ficant mode competition between the modes TE11 and TM01 is present. Fo r applications such as accelerator drivers, amplifiers or phase-locked oscillators at frequencies in the 11-33 GHz range with high peak powe r (> 100 MW) are required. A 17 GHz CARM amplifier experiment and a 17 GHz third harmonic gyro-amplifier experiment are presently under way. These devices utilize the SRL/MIT SNOMAD II linear induction accelera tor injector for production of a 30 ns flat top electron beam up to 40 0 keV and 400 A. The third harmonic gyro-amplifier operating in the TE 31 cylindrical wave guide mode has produced 5 MW of RF power with over 50 dB of gain at 17 GHz. Because of its high power output the gyro-am plifier will be used as the RF source for a photocatode RF electron gu n. A CARM experiment designed to operate in the TE11 mode is also disc ussed.