Scaling laws and power limits for klystrons

The various phenomena which limit the operating voltage of klystrons are described. These include gun arcing, Kilpatrick´s criterion for r-f gap arcing, and cavity r-f power density. Factors affecting beam current such as space-charge effects, pulse length, and beam tunnel area are also examined. The peak power capability of klystrons may be described as a function of wavelength by two overlaid sets of curves in which operating voltage, perveance and pulse length are parameters. The average power capabilities and scaling laws for various single-mode-waveguide output windows are described. The theoretical limits described above correlate well with power levels reached by existing klystrons and predict directions for development of much more powerful klystrons. The limits described apply not only to conventional klystrons, Out also to Clustered-Cavity^TMKlystrons, so it is possible to consider the development of multimegawatt or even gigawatt klystrons with bandwidths in excess of 30%.