Effects of photostimulation in natural zircon

Effects of optical stimulation were studied in unirradiated as well as in X, ββ and VUV irradiated natural zircon crystals. Various optical and dosimetric properties were investigated and in particular thermoluminescence (TL) and optically stimulated thermoluminescence (OSTL or PTTL), as well as optically stimulated luminescence (OSL). After X or ββ irradiation at RT, main TL peaks appeared in the samples at about 354, 385 K and weaker ones at about 470, 520 and near 600 K. TL could also be excited by monochromatic VUV radiation. Results show that the same traps are responsible for the TL induced by VUV as by X or ββ irradiation. In pre-irradiated samples, a notable OSTL was recorded below RT as well as at about 420 K. The same emission bands appeared in the XL as in various TL and OSTL peaks, indicating the same luminescence centers are involved in these emissions. OSTL stimulation spectra showed maxima at 425 and 294 nm. Prolonged illumination with these wavelengths also caused a notable decrease in the OSTL; this bleaching effect is attributed to the depletion of the carriers from the trap responsible for the phototransfer. The TL sensitivity of the main TL peaks below 400 K was ∼110 of that of TLD-100, and that of the higher temperature TL peaks was even lower by 1–2 orders of magnitude. The TL peaks below 400 K are subject to fast thermal fading at RT. The application of the OSTL method may therefore be preferable to the regular TL method in these crystals.