Study of the optical properties of etched alpha tracks in annealed and non-annealed CR-39 polymeric detectors

• UV–visible absorption through etched alpha tracks in annealed and non-annealed PADC films was investigated.
• Films of PADC based NTDs were irradiated with different fluences from alpha particles.
• PADC film samples were annealed at a temperature of 120 °C for durations of 2, 4, 6, 8, and 10 h.
• It is a good method for relative fluence or dose reading.

The UV–visible absorption spectra of virgin and alpha particle-irradiated, annealed and non-annealed CR-39 polymeric track detectors were investigated using a UV–visible spectrometer (Shimadzu mini 1240). Isothermal annealing experiments were carried out on poly allyl diglycol carbonate (PADC) films based nuclear track detectors (NTDs) exposed to a 241Am source. A shifting and broadening of the UV–visible peaks was observed as a result of the etched alpha tracks in the non-annealed and annealed PADC films. The UV–visible spectra of the virgin and non-annealed α-irradiated PADC polymer films displayed a decreasing trend in their optical energy band gaps, both direct and indirect, whereas those measured for the annealed α-irradiated ones showed no significant change. This drop in the energy band gap with increasing fluence is discussed on the basis of the alpha particle- and thermal annealing-induced modifications in the PADC polymeric detector. The results clearly showed that the values for the indirect energy band gap were lower than the corresponding values for the direct band gap. In addition, the Urbach energy was estimated from the Urbach edge, and exhibited roughly the same trend as the optical band gap. Finally, this study presents new results showing that the annealed PADC films were highly insensitive to alpha particles.