Experiments in modulating an electron beam of power greater than 30 GW revealed a mechanism that limits the output RF power of the NRL relativistic klystron amplifier. This mechanism is beam loading of high voltage gaps. It is found that the presence of charge at the gaps is analogous to connecting a capacitor in parallel with the HV gap. This capacitor has a component that depends only on the electron density and on the geometry. Its presence causes detuning of the cavity, resulting in a slow build-up time for the electron beam modulation, saturation of the RF current amplitude and occasionally erratic fluctuations in the RF current. The nonlinear components of this capacitor cause the spectrum of the current modulation to be shifted toward the high frequencies.

Date Published: 1 April 1990
PDF: 10 pages
Proc. SPIE 1226, Intense Microwave and Particle Beams, (1 April 1990); doi: 10.1117/12.18539

Published in SPIE Proceedings Vol. 1226:
Intense Microwave and Particle Beams
Howard E. Brandt, Editor(s)