Effect of velocity spread on operation of high power gyrotrons
Summary form only given, as follows. The effect of velocity spread on the operation of 140 GHz gyrotrons has been studied. The performance of two cavities, with low and high Q, has been examined experimentally and theoretically. The simulation code MAGY was modified to include the measured velocity distribution function and the measured pitch angle in order to compare the measured efficiencies with the predicted efficiencies. Based on measurements, the inferred velocity spread at a beam current of 40 A is given by (/spl delta/v/sub /spl perp///v/sub /spl perp//) RMS=15%. Simulations with this spread produced efficiencies lower than those measured. However, it was found that assuming /spl delta/v/sub /spl perp///v/sub /spl perp//=10% for 40 A current and using the experimentally determined dependence of the spread on the current the calculated efficiencies agree well with the measured efficiencies for the low 8 cavity. The efficiency of the low Q gyrotron at 40 A beam current is only 27%. For the same beam current and velocity spread the efficiency of the high Q gyrotron was predicted to be 40% which agrees well with the measured efficiency of 39%.