Experimental studies of a high power, X-band, coaxial gyroklystron

Gyroklystrons are possible candidates for the RF sources in future linear colliders, A two-cavity and a three-cavity X-band gyroklystrons have been designed, built, and tested on the new 100 MW test bed at the University of Maryland, The theoretical design of the three-cavity X-band gyroklystron called for a peak power of 96 MW at an efficiency near 40% at a frequency of 8.568 GHz. In experiments, peak output power in the range of 75-85 MW at a frequency of 8.6 GHz has been measured with the three-cavity gyroklystron tube. The three-cavity tube was operated at electron beam voltage and current of 470 kV and 500 A, respectively. The efficiency is approximately 32% and the gain is approximately 30 dB, The pulse width of the output power signal is 1.7 mu s (full width at half maximum), while pulse repetition rate was limited to 2 Hz in this proof-of-principle study. This paper details the design, performance, and diagnostics of these two X-band gyroklystrons operating at the fundamental cyclotron resonance.