A high peak power electrostatically focused klystron amplifier in S-band

This paper describes the development of the L-3975, a high peak power klystron amplifier in S-band utilizing electrostatic focusing for beam confinement. The design objectives are: operating frequency, 3000 mc; peak power output; 1 MW; average power output, 5 KW; beam voltage, 100 KV max.; bandwidth, 5%; gain 36 db. This development program is significant because it is the first attempt to utilize electrostatic focusing in a high peak power tube. The paper will review in detail the design considerations and design techniques pertinent to an electrostatically focused klystron at this voltage and power level. The focusing utilizes the periodic electrostatic einzellens principle first applied to klystrons by R. Hechtel. A critical design parameter limiting the usable beam voltages is the voltage gradient between the focusing lens and the klystron body. The L-3975 operates with a gross voltage gradient of 442V/mil. Experimental results show a voltage hold-off gradient in excess of 552V/mil for the lens configuration use in the design. The first experimental model of this tube is presently on test and detailed test results will be discussed in the paper.