The light sensitivity of thermoluminescent materials:: LiF:Mg,Cu,P, LiF:Mg,Ti and Al2O3:C

Many thermoluminescence dosimetry (TLD) materials exhibit a variation in read-out with light exposure (including both visible and UV radiation energy) which may cause problems in environmental dosimetry. The aim of the present study was to investigate this for three newer preparations of TLD material - LiF:Mg,Ti (GR-100, DML, China), LiF:Mg,Cu,P (MCP-N, TLD Niewiadomski & Co., Poland) and Al2O3:C (Stillwater Sciences, USA). TLDs irradiated to 1 or 10 Gy were exposed to light from a calibrated spectral lamp with three to four times higher UV component than sunlight. MCP-N proved to be approximately five times less light sensitive than GR-100. For both materials, the decay of the major glow peaks with increasing light exposure could be described by a single or dual exponential equation. Half lives for the major dosimetry peaks of GR-100, fit to a single exponential, were 1132 min (similar to 19 h) for peak 4 and 275 min (similar to 41/2 h) for peak 5. The half lives for peak 4 of MCP-N, fit to a dual exponential, were 309 min (similar to 5 h) and 6627 min (similar to 41/2 days). For MCP-N, this relates to approximately a loss of half the signal in 14 days of sun exposure (Polish summer). The readout of Al2O3:C increased with increasing light exposure and saturated after only 5 min at a level 26 times higher than the signal without light exposure. (C) 2000 Elsevier Science Ltd. All rights reserved.