Time-resolved measurement of the energy distribution function of an electron beam created by a transient hollow cathode discharge

The energy distribution function of the electron beam produced in a transie nt hollow cathode discharge is measured using a method which is based on th e collector self-biasing, allowing an access very close to the extraction h ole. The distribution obtained is a mainly polyenergetic one extending over a range of up to some tenths of kiloelectronvolts. It is composed both of runaway electrons, whose energies we assume are equal to the instant discha rge voltage, and a main part composed of a monotonically decreasing energy distribution. The ratio between these two populations is around 10% and str ongly increases with distance from the extraction hole.