Using Atomic Force Microscopy to study X-ray Induced Reduction in CR-39 Sensitivity*

CR-39 is a solid-state nuclear track detector fielded in many diagnostics used to diagnose a large range of high energy density physics experiments. CR-39 displays ~100% efficiency for detecting charged fusion products within its sensitive energy range. However, when exposed to x-rays, CR-39 loses some of its sensitivity. Presented here are the results of experiments in which pieces of CR-39 were dosed with varying amounts of x-rays; the CR-39 was subsequently irradiated with DD protons and etched in NaOH at 80C. The etched CR-39 pieces were subsequently scanned with an atomic force microscope to obtain the track diameters, depths, and other topographic information that cannot be obtained through typical optical microscopy. The bulk etch rate and track etch rates were determined for each x-ray dose and the differential sensitivity between the x-ray irradiated and unirradiated regions was inferred. The observed change in track properties can be explained by x-ray exposure increasing both the track and bulk etch rates, hence decreasing the CR-39 sensitivity.