Analysis of a 34 GHz peniotron oscillator

Preliminary results from the UC Davis peniotron experiment have been previously reported. The device operated, as designed, in the second cyclotron harmonic at the expected frequency of 34 GHz in the fundamental cavity mode. However, the device produced maximum output power at lower than expected voltage. Furthermore, a competing mode was present at the lower end of the magnetic tuning range which interfered with the peniotron mode and likely resulted in decreased power output. This mode was determined to be the fourth-harmonic gyrotron mode and was unexpected at the design beam current of 3.5 A used in the experiment. In fact, measurements of this gyrotron mode indicated a start current comparable to that of the design peniotron mode. The initial estimate of maximum output power was approximately 30 kW peak. However, the output coupling scheme of the device is being examined and re-calibrated to provide final values. The Q of the 4-vane interaction cavity at the competing mode frequency is also being analyzed and measured in an effort to explain the mode competition. The device was also observed to operate in a linear polarized peniotron mode for some regimes of beam voltage and beam alpha. This is also being investigated in terms of the interaction cavity parameters and gun performance. Results of the analysis will be presented along with final efficiency and power values.