Experimental studies of a multi-megawatt, 19.7 GHz harmonic gyroklystron

Summary form only given. Experimental progress in the development of a two-cavity gyroklystron employing a 19.7-GHz, TE/sub 021/ second-harmonic output cavity and a 9.85-GHz, TE/sub 011/ fundamental input cavity is discussed. Output powers in excess of 7.5 MW for 0.5 /spl mu/s, at 11% efficiency and 20 dB gain, have been achieved with a 410 kV, 162 A, /spl alpha/ /spl ap/ 0.9 electron beam. Optimum performance required a magnetic field profile with an 8% up-taper between the input and output cavities. Studies of frequency response, output power vs. input power, and radiation power patterns at this and other operating points have been performed. Performance-limiting 6-8 GHz whole tube instabilities have been characterized, and improved suppression methods have been examined.