Estimation of the time elapsed between exposure and readout using peak ratios of LiF:Mg,Cu,P (MCP-N, GR200A)

The applicability of peak area ratios (peak2/peak4 and peak3/peak4) in the glow curves of LiF:Mg,Cu,P for the estimation of time between exposure and readout, t(ER) was studied. MCP-N and GR-200 LiF:Mg,Cu,P detectors were exposed to simulate an 'accidental' dose at times before readout ranging from 24 h to 3 months. Two groups of detectors were exposed simultaneously to determine the fading of irradiated detectors and the sensitivity variations of stored, non-irradiated detectors. Peak areas were evaluated using a computerised glow curve analysis code. The peak 2/peak 4 ratio is well suited for evaluating t(ER) below 1 week, while the peak 3/peak 4 ratio serves for t(ER) up to 3 months. The method can be applied in personal and environmental dosimetry to evaluate the date of a high dose rate, accidental exposure.