Experimental studies of stability and amplification in a two-cavity second harmonic gyroklystron

We report the operating characteristics of a sequence of two-cavity second harmonic gyroklystrons which are derived in part from a previous fundamental tube and utilize output cavities which resonate at twice the drive frequency. We present results from the design simulations as well as details of the stable range of operating parameters. While the harmonic tube is somewhat more susceptible to spurious oscillations and more sensitive to parameter variations than the fundamental device, there is still considerable parameter space available for amplifier operation. Peak powers above 30 MW are obtained with efficiencies greater than 28% and large signal gains of 27 dB. These results depend critically on the magnetic field profile which has a slight up-taper at the optimum operating point. The nominal beam parameters include a pulse length of 1 /spl mu/s, a voltage near 450 kV, a current in the range 235-245 A, and a perpendicular to parallel velocity ratio (/spl alpha/=v/sub /spl perp///v/sub z/) near one.<
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