DETERMINATION OF THE CRITICAL ANGLE OF TRACE REGISTRATION IN PROTON-IRRADIATED AND CHEMICALLY ETCHED CR-39 DETECTORS

The computation of the neutron response of a nuclear etched track dose meter needs the quantitative characterisation of the track formation p rocesses caused by neutron induced charged particles. Experimental and theoretical procedures have been developed in former studies in order to determine the bulk etch rate and the track etch rate as functions of the initial particle energy and etching time. These studies carried out for proton tracks in CR-39 included the derivation of the critica l restricted energy loss which forms the basic criterion for producing etchable tracks. Further evaluation of the time dependent etch rates allowed determination of the critical angle of proton incidence as a f unction of the proton energy and the etching time. The results depend not only on the etching conditions but also on the spatial resolution of the optical system used for detector evaluation. This was, likewise , found for the energy limits of proton detection resulting from the b orderline case where the critical angle drops to zero. The results all ow prediction of whether a proton of given energy and direction will b e able to produce a visible track under given etching and evaluation c onditions. Extending this method to other neutron induced charged part icles, the neutron response of a CR-39 dosemeter can be computed on th e basis of a concept developed in a former study.