An L-band 100 kW CW klystron for FEL driver accelerator

A 100-kW CW, L-band, narrow-band klystron was developed to drive the cryogenic cavities in the injector stage of the FEL driver accelerator. The klystron was designed to be especially stable and robust under variable conditions. The klystron output circuit will be buffered by a circulator, because the superconducting cavity can appear as a short circuit and reflect all of the power over a short period of time. In order to cope with the changing load conditions, the electron optics incorporate a very stiff 33.5-kV beam, and the output cavity was designed to be load-VSWR tolerant. Consequently, the body current under saturated conditions is less than 14 mA, or 0.002 percent of the 6.6-ampere beam current.