Conditioning and simulations for the one-microsecond, one kilojoule per-pulse L-band relativistic klystron

Summary form only given, as follows. The development of a high-current relativistic klystron amplifier (RKA) is continuing at Los Alamos. The goal is to produce 1 kJ per pulse, with a one-microsecond pulsewidth, and a peak power of 1 GW. The three cavity tube has already produced pulses with more than 150 J and over 450 MW peak power: The output power has been limited by breakdown In the output cavity. A novel scheme for ex-situ conditioning of the output cavity gap pieces is being developed. A specialized cavity with a high Q, that holds the gap pieces in the same geometry as in the tube, is used in conjunction with a high power commercial klystron to field condition the surfaces. Results from this work and recent PIC code simulations will be presented.