EXPERIMENTAL STUDIES OF STABILITY AND AMPLIFICATION IN A 2-CAVITY 2ND-HARMONIC GYROKLYSTRON

We report the operating characteristics of a sequence of two-cavity se cond harmonic gyroklystrons which are derived in part from a previous fundamental tube and utilize output cavities which resonate at twice t he 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 a nd more sensitive to parameter variations than the fundamental device, there is still considerable parameter space available for amplifier o peration. Peak powers above 30 MW are obtained with efficiencies great er than 28% and large signal gains of 27 dB. These results depend crit ically on the magnetic field profile which has a slight up-taper at th e optimum operating point. The nominal beam parameters include a pulse length of 1 mu s, a voltage near 450 kV, a current in the range 235-2 45 A, and a perpendicular to parallel velocity ratio (alpha = upsilon( perpendicular to)/upsilon z) near one.