A new electron beam accelerator with the beam ejection into the atmosphere has been recently developed for radiation technology application. A high-voltage nanosecond pulse generator of the accelerator is based on a low-inductance pulse transformer. The energy stored in the high voltage capacitor bank is transferred through a step-up pulse transformer to a vacuum electron diode at triggering of a cold cathode thyratron. The electron diode consists of a metal-ceramic explosive emission cathode, which provides a high delay time in the plasma formation. The electron beam current pulse duration at half height is 75 ns. The kinetic energy of the electron beam is 450 keV with the energy of extracted electron beam of up to 10 Joules/pulse. The accelerator is capable of operating in a long-term repetition rated system, producing up to 40 pulses per second, which is possible due to the use of both a built-in system of regeneration and cooling of the transformer oil and an additional cooling system of an exit window foil. The results of shot-to-shot variation of the beam parameters in the frequency mode are presented.