Investigation of anode foil stability at high-current electron accelerator

Results of experimental studies of anode foil destruction mechanisms are presented. The experiments have been done on the accelerator with the following parameters: voltage - up to 500 kV, e-beam current - up to 10 kA, pulse duration (FWHM) - 60 ns, pulse repetition rate - up to 3 Hz. It was found out that the formation of cathode spots on the anode foil surface as well as the current in the diode during the positive post-pulses following the main negative pulse of the accelerating voltage are the main reasons for the foil life time limitation. The improvement of the diode impedance matching with the output impedance of the pulsed power generator decreases the energy of the post-pulses and leads to a longer life time of the anode foil. The introduction of an additional anode electrode forming with the cathode a vacuum crowbar switch practically excludes damages of the anode foil and increases its life time up to 10⁵ pulses.