2.2 MW, 165 GHz coaxial cavity gyrotron

Measurements on a coaxial gyrotron equipped with modified components have been performed. In experiments a maximum rf-output power of 2.2 MW with an output efficiency of 28 % has been obtained. A maximum efficiency of 30% (48% with depressed collector) has been achieved at the nominal output power of 1.5 MW. The mechanical stability of the insert under operating conditions has been found to be within +/- 0.03 mm which is sufficiently low for stable long pulse operation. Parasitic low frequency oscillations have been identified to be generated either inside the mirror box (474 / 386 MHz) or in the cathode region (21 / 82 MHz).