Compact millimeter wave cyclotron resonance maser

The building of the gyrotron chamber and associated apparatus is described. The system is operational and measurements have begun. Using only 50 kW of the 200 kW available from the X-band magnetron, the rf accelerator produced 100 mA, 100-250 keV beams. Millimeter wave measurements were made. The second gyrotron cavity, which was designed to be excited by approximately 150 keV beams, yielded approximately 100 W at 26-46 GHz, which corresponds to 1% electron to output wave energy conversion efficiency. This cavity was designed to be undercoupled due to start oscillation considerations. The efficiency of electron energy into cavity wave power was on order of 5%. The next cavity tested is critically coupled for higher power operation. Activities include a theoretical description of the large orbit cyclotron harmonic maser which yields encouraging values for device efficiency. Efficiencies as high as 8% are predicted at millimeter wavelength operation with a uniform magnetic field. A small signal theory of the harmonic gyrotron is developed which yields the value of beam current necessary for oscillation.