TIME-RESOLVED MICRODOSIMETRY IN A QUASI-MONOENERGETIC NEUTRON BEAM

Timing characteristics of commercial Rossi-type proportional counters operating at low gas pressures were studied in a pulsed neutron beam of nominal energy 63 MeV. The correlation between electron drift and counter dimensions is demonstrated from TOF measurements performed in normal and helix modes. By identifying each registered pulse height event with its own time-of-flight, it is shown that the timing response is masked by amplitude walk derived in the time pick-off. The inherent response of the counter in helix mode is revealed after accounting for time slewing and compares favourably with that of an NE213 liquid scintillator. Distinct structure associated with the incident energy spectrum is discernible and enables the unambiguous selection of energy deposition events resulting from neutrons of the nominal energy.