Optimization of the output cavity for a three cavity X-band gyroklystron amplifier

Experimental results of the University of Maryland three-cavity gyroklystron indicate that interactions past the output cavity have enhanced the tube´s efficiency. The tube operated at 10 GHz in the TE01 mode. At beam parameters of 425 kV, 204 A, and α=0.7, the three-cavity gyroklystron produced 27 MW at 32% efficiency with gain of 36 dB and pulse energy of 39 J [1]. Four different three-cavity circuits were studied experimentally. These circuits differed mainly in the geometry of the output cavity. Each of these circuits was found to have two distinct operating regimes, which were controlled by the magnetic guide field taper across the circuit. By observing the effects of perturbing the guide field after the output cavity; and using an electric field probe in the output cavity it is shown that one regime corresponds to a CARM-like interaction after the output cavity.