Alpha Particle Track Detection with Celluloid Films

Abstract

We propose to define a “practical” critical energy E c as the energy at which the experimental detection efficiency of α-particles with celluloid SSTD is just 50 per cent. The values of E c at an incident angle θ=45° were measured as functions of etching time. It was also observed that the values of E c were increased by appropriate irradiation with ultraviolet light of 2537A. An “intrinsic” critical energy e c (θ) is proposed to be defined as the energy at which the etching rate along the track V T is equal to V G /sin θ, where V G is the etching rate of the detector material itself. The value of e c (90°) was deduced from the observed values of E c (45°) to be e c (90°)=2.72±0.10 MeV, being independent of the sorts of celluloid tested (Daicel and another one) and of UV irradiation.