Experimental determination of alpha particle etchable track lengths in thermally treated CR-39 detectors demonstrates the existence of significant chemical changes

Abstract

In the present work, a clear-cut determination of alpha particle track length in poly allyl diglycole carbonate (PADC) polymer-based nuclear track detectors NTDs (called CR-39) has been performed. We have applied the Over-Etched Track Diameter (OETD) method to determine the alpha particle etchable lengths in both non-thermally treated (pristine) and thermally treated CR-39 detectors. The diameters of etched alpha tracks in pristine and thermally treated CR-39 detectors have been measured as a function of etching time at different heating temperatures and times, using a 241Am radioactive source with alpha particles of specific energy of 5 MeV. This is the first-time etchable lengths of alpha particles have been determined in thermally treated CR-39 detectors. The results of the OETD method for the etchable lengths of alpha particles in non-thermally treated CR-39 detectors are in an excellent agreement with the previously published data and with the calculated lengths. On the contrary, the etchable lengths determined for thermally treated detectors are smaller than expected track lengths, the higher the heating times and temperatures. These results are discussed in the light of our understanding of the effects of thermal treatment in the polymer material that makes up CR-39.