Track like structures in CR-39 detector from alpha particles with incident angles close to and below the critical angles

Abstract

ABSTRACT The critical angles for the CR-39 detector were studied. In the first step, CR-39 detectors were irradiated with alpha particles with normal incidence to the detector surfaces, and with alpha particles in the energy range from 1 to 5 MeV. The detectors were etched in 6.25 N NaOH solutions kept at 70 °C. The track diameters were fit by a V function, which has a maximum value of 2.87, so the critical angle should be 20.4°. Therefore, at incident angles at or smaller than 20°, no tracks should be observed. The next step was the irradiation of the detectors under small incident angles, namely, 20° and 10°. Track-like structures were indeed observed under the optical microscope. A model taking into consideration the finite lateral dimension of the latent track was proposed to explain such track development.