Efficiency estimation for detecting U alpha particles in solid-state nuclear track detectors.

The detection efficiencies of solid-state nuclear track detectors, made with cellulose nitrate materials (LR-115 II) or allyl diglycol carbonate (CR-39) were investigated. Detection efficiency for a surface alpha source was experimentally obtained by changing the dimensions between the detector and the source, while alpha-particle incident efficiency was calculated. The ratio of the detection efficiency to the incident efficiency was then determined. It was confirmed that the ratio for LR-115 II was dependent on energy, but for CR-39 the ratio showed almost no dependency. Considering the relationship between solid absorber thickness and detection efficiency of the surface alpha source, detection efficiencies of U in various metals were estimated. The efficiency for U contained in Al and Fe was proposed as 16% for LR-115 II and 22% for CR-39. Using these efficiencies, amounts of U in some Al and Fe ingots were determined. These agreed with concentrations obtained by neutron-activation analysis with deviations of less than 15%.