DIRECT MEASUREMENT OF THE CRITICAL ANGLE OF INCIDENCE IN ELECTROCHEMICALLY ETCHED CR-39 AND MAKROFOL DETECTORS

A very simple experimental method has been developed for the direct measurement of the critical angle using a single detector covering a cylindrical holder. On the basis of one irradiation only, all angles of interest between the detector coordinate and angle of incidence may be investigated using transformation formulas. In such a way, the critical angle of incidence has been measured for alpha particles in Makrofol DE, and alpha particles and protons in CR-39 under two commonly used electrochemical treatments: (a) combined chemical pre-etching and electrochemical etching; and (b) combined low and high frequency electrochemical etching. The influence of some parameters, e.g. particle energy, electric field strength and etching time, has also been studied.