Design and operation of a high power, high efficiency, L-band multiple beam klystron

CPI has designed and is currently in the process of building a prototype of a horizontally oriented, ges10 MW, ges65% efficiency multiple beam klystron (MBK) operating at 1300 MHz. The klystron, designated the VKL-8301B, was ordered by DESY for the European XFEL. The klystron was designed using of sate-of-the-art multi-dimensional design codes to ensure that all performance requirements are exceeded. Initial rf hot test data at reduced duty and pulse width produced a peak saturated rf output power in excess of 11 MW and 70% efficiency, which was however accompanied by high beam interception. Operation at full duty and pulse width as well as adjustment of the focusing and retuning the cavity frequencies impacted output power and efficiency. A compromise was found to satisfy all required operating conditions, including operation into a higher output mismatch. Complete test results will be presented at the conference.