Response functions for proton-recoil proportional counter spectrometer
Abstract
The accurate determination of neutron spectra with proton-recoil proportional counters requires that corrections be made for non-ideal electric-field effects and for wall-and-end effects. The use of field tubes to define a sensitive volume leads to a distortion of the internal field lines near the ends of the sensitive region and produces a counter whose multiplication is a function of position of the event along the anode. Wall-and-end effects are present when some proton-recoil tracks deposit only part of their energy in the sensitive region of the counter. Correction schemes have been obtained for electric-field distortion based on the solution of the electric field everywhere in the counter together with measured multiplication versus voltage data and for wall-and-end distortion based on analytically determined track length probability functions and measured stopping-power and range-energy data. The investigation of electric-field effects indicated that by using an unconventional counter design in which the diameter of the cathode over the field tube is reduced, it is possible to reduce the influence of electric-field distortion and produce a counter better suited for spectroscopy and absolute counting applications. Calculated pulse-height distributions have been compared with experimentally determined distributions. The extent of corrections for these effects has been assessed for a representative fast-reactor spectrum.
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