Performance of an S-Band Klystron at an Output Power of 200-MW

In order to provide RF power to the accelerating sections of a future S-Band linear collider, klystrons producing 150MW of output power at a frequency of 2.998GHz are required. Two S-Band klystrons with a nominal output power of 150MW at a pulse duration of 3ps and a repetition rate of 50Hz were developed in a collaboration between SLAC, Philips, TH Darmstadt and DESY [1]. They were built and successfully tested at SLAC in 1994 and 1995 and then shipped to DESY to feed the accelerating sections of the S-Band test facility linac. In order to explore their power potential one of the klystrons was operated at an even higher output power of more than 200MW at the test facility. HV pulses up to 610kV at a current of 780A were applied to the klystron cathode. This paper reports the results of the measurements of the various parameters of the klystron at this power level (e.g. output power, efficiency, perveance). It describes the performance and the limitations of the klystron in this power range