Afterglow and thermoluminescence properties in HPHT diamond crystals under beta irradiation

The behaviour of afterglow (AG) and thermoluminescence (TL) in nine beta‐irradiated HPHT Ib type diamond crystals is presented. The transparent yellow synthetic crystals (Sumicrystal, UP‐3510) were purchased from ProDiamond, Germany. Immediately after irradiation, the crystals exhibit pronounced AG (phosphorescence) caused by thermal emptying of the traps responsible for the low temperature TL peaks. All AG decay curves are well fitted with the sum of one, two or three exponential decays with the same decay lifetimes of 6.73, 12.8 and 145 s for the fast, medium and slow decay components, respectively. Two different groups of AG decay curves can be distinguished. The first group (three crystals) exhibits intense AG related to fast emptying of some shallow traps. The initial AG intensity of other crystals (second group) is 2–3 order lower than those of the first group crystals. This difference is due to the absence (or very low intensity) of the shallow traps in these crystals. TL glow curves consist of two sets of peaks. The first one with peak maxima at about 50, 70, 180 and 280 °C has high sensitivity but saturates at doses higher 1 Gy. The second set looks like several strongly overlapped TL peaks that exhibit linear–sublinear behaviour. The intensity of the TL peaks of the second set correlates with the intensity of TL below 100 °C. TL glow curves recorded immediately after beta irradiation with indicated doses; the initial part of the curves (below 30 °C) corresponds to AG at room temperature. The inset shows the dose growth of integrated TL between 30 and 330 °C.