Impact of high doses of quasi-monoenergetic X-rays on the response of CR-39 to protons and alphas*

CR-39 is a solid-state nuclear track detector that is commonly used to detect protons and alphas in high-energy-density physics (HEDP) experiments. Since there is always an intense X-ray background in such experiments, understanding how X-rays impact the response of CR-39 to protons and alphas is crucial for accurate measurements. Others have investigated the response of CR-39 to a bremsstrahlung X-ray spectrum [1, 2], however, it is unclear how monoenergetic X-rays affect the response of CR-39. Here, quantitative studies of the effects of quasi-monoenergetic X-rays upon the proton and alpha signals in CR-39 are presented. Multiple pieces of CR-39 were illuminated with Ti, Cu, Mo, or W K-line X-rays followed by illumination of DD or D³He protons and Am-241 alphas. Preliminary results show that the W X-rays affect the inferred fluence of the protons and alphas on the CR-39 and decrease the track sizes of both species. Absolutely calibrated radiochromic film is used to measure the X-ray dose on the CR-39 to quantify how the inferred fluences and track sizes of protons and alphas depend on X-ray dose. For low doses, it is found that increasing the etch duration of the CR-39 can at least partially recover fluence and track diameter data from CR-39 irradiated with X-rays.

[1] J. Rojas-Herrera et al., Rev. Sci. Instrum. 86 (3), 033501 (2015).

[2] H. G. Rinderknecht et al., Rev. Sci. Instrum. 86 (12), 123511 (2015).