Development of a high power and long pulse gyrotron with collector potential depression

A design and experimental results of a 110 GHz gyrotron with a single stage depressed collector are presented. By recovering a spent beam energy, efficiency of the gyrotron was improved from 30% to 50% with the RF output power of 610 kW and the pulse duration of 50 ms. A stable 5 sec oscillation was performed at 350 kW (output energy 1.75 MJ) with high efficiency of /spl sim/48% and the 420 kW-3.3 sec oscillation was also obtained. Conditioning time was short compared with the conventional gyrotron since a collector heat load was significantly reduced by the application of the beam retarding voltage.<>