Automatic spark counting of alpha-tracks in plastic foils

Abstract

The possibility of α-track counting by jumping-spark counter in cellulose acetate and polycarbonate nuclear track detectors was studied. A theoretical treatment is presented which predicts the optimum residual thickness of the etched foils in which completely through-etched tracks (i.e., holes) can be obtained for α-particles of various energies and angles of incidence. In agreement with the theoretical prediction, it is shown that a successful spark counting of α-tracks can be performed even in polycarbonate foils. Some counting characteristics, such as counting efficiency vs particle energy at various etched-foil thicknesses, surface spark density produced by electric breakdown in unexposed foils thickness, etc., have been determined. Special attention is given to the spark counting of α-tracks entering thin detectors at right angle. The applicability of the spark-counting technique is demonstrated in angular-distribution measurements of the ²⁷A1 (p,α₀)²⁴Mg nuclear reaction at E_p=1899 keV resonance energy. For this study 15 μm thick Makrofol-G foils and a jumping-spark counter of improved construction have been used.