decrease in the dead time of proportional counters of neutrons after exposure to pulsed fluxes of ionizing radiation

Abstract

During irradiation of a proportional counter with a high-power bremsstrahlung flux, a high density of charged particles arises in the interelectrode gap owing to primary and secondary ionization. Charge separation in the interelectrode gap induces an internal electric field that leads to a decrease in the gas-amplification factor to a level below the neutron-recording threshold. The delay time of neutron recording (dead time) by the counter after a bremsstrahlung burst may exceed 100 µs. A device developed for switching a high voltage applied to the counter for the bremsstrahlung emission time is described, as are experiments on detection of prompt fission neutrons emitted after irradiation of the fissile substance with a pulsed bremsstrahlung flux. The results show that, when this device is used, the neutron-recording delay time decreases severalfold.