Low energy alpha particle tracks in CR-39 nuclear track detectors: Chemical etching studies

The widely known CR-39 nuclear track detectors (NTDs) have been used to investigate the etch pits formed by alpha particles from a 241Am source moderated to 1–2 MeV. The efficiencies of two available CR-39 plastic detectors, Lantrak and Baryotrak, have been studied as a function of the chemical etching time. The chemical etching solutions of the NaOH, KOH and NaOH+ethyl alcohol at 70 and 80°C have been applied to build etch pit diameter growths as well as density curves. The obtained growth curves of etch pit diameters have been compared under these different etching conditions, showing similar general trends for Baryotrak and Lantrak detectors for etching at 70°C. A slight divergence of the curves have been observed at 80°C for etching times above 400 min, revealing a small variation in the bulk etch rates between the two detector types. The etch pit density curves for both detectors have also been studied, showing a plateau for all etching conditions except for NaOH+ethyl alcohol at 80°C, in which there is a significant decrease in density after ≈ 600 min of etching. The results obtained with the protocols described in detail in this work show the pertinent precautions to be adopted in the chemical treatment of NTDs for the detection of alpha particle at low energies. In particular, the quantitative results highlight the limits of linear growth of pits and induction etching time for etch pits with diameters D=0 μm (EIT0) and D=1 μm (EIT1).