Experimental and theoretical development towards a 500 MW, one-microsecond, L-band relativistic klystron amplifier

Abstract

This paper describes the experimental development of a long pulse, high current, annular beam relativistic klystron amplifier. The desired performance parameters are 1 GW output power and 1 μs pulse length with an operating frequency of 1.3 GHz. The electron beam voltage and current are nominally 600 kV and 5 kA. Peak powers approaching 500 MW have been achieved in pulses of 1 μs nominal baseline‐to‐baseline duration. The half power pulse width is 0.5 μs. These pulses contain an energy of about 160 J. The design of this class of tube presents some unique challenges, particularly in the output cavity. The output cavity must exhibit a very low gap shunt impedance in order to obtain reasonable conversion efficiency from the low impedance modulated electron beam to microwave power, while still maintaining a reasonable loaded Q for mode purity. The physics of this device is dominated by space charge effects which strongly impact the design. Current experimental results and theoretical design considerations for this class of tube, and scaling to higher frequency operation, suitable for the Next Linear Collider are discussed.