Low energy alpha particles dose mapping with a combination of CR-39 detector and a high resolution flatbed scanner

Abstract

The potential of a combination of the well-known CR-39 detector and a high-resolution flatbed scanner for low energy alpha particles dose mapping is investigated. The CR-39 detectors were irradiated with perpendicular incident 4 MeV alpha particles of doses 0.009, 0.018, 0.033, 0.051, 0.067, 0.134, and 0.164 Gy, thereafter, etched in 6.25 N NaOH at 70 °C. The CR-39 detectors were scanned with Canon CanScan 9000F Mark II of spatial resolution of 9600 dpi and color depth of 48 bit. The measurements reveal that the pixel values for different color channels are correlated linearly with 4 MeV alpha particles dose at the etching times of 2 h, 3 h, and 4 h. For blue channel, the maximum sensitivity was -53178  1463 pixel value/Gy at etching time of 4 h, compared to -15290  2004 pixel value/Gy, and -42255  840 pixel value/Gy at 2 h and 3 h respectively, the negative sign indicates the pixel values decrease as the 4 MeV alpha particles dose increases. While for etching times, 5 h and 6 h, the pixel values decrease exponentially as the 4 MeV alpha particles dose increases. For prolonged etching time, the pixel values are non-monotonic function of alpha particles dose. The optical density was evaluated as a function of etching time (removal thickness) of CR-39 irradiated with different doses. For 0.009 Gy, and 0.018 Gy doses of alpha particles, the optical density is linearly correlated with the etching time; for other doses, the optical density is not a monotonic function of the etching time. These new findings pave the way to use the combination of the CR-39 detector and high-resolution flatbed scanner for dose mapping of alpha particles and heavy ions over large-scale areas, applying etching conditions for each particle type and corresponding energy, that produce maximum sensitivity and linearity.