  The radio-photoluminescent (RPL) characteristics of LiF:Mg,Ti (MTS) and
LiF:Mg,Cu,P (MCP) thermoluminescent detectors, routinely used in radiation
protection dosimetry, were investigated after irradiation with ultra-high
electron doses ranging up to 1 MGy. The photoluminescence of both types of LiF
detectors was stimulated by a blue light (460 nm) and measured within a
spectral window around 530 nm. The RPL dose response was found to be linear up
to 50 kGy and sublinear in the range of 50 kGy to 1 MGy for MCP detectors and
linear up to 3 kGy and next sublinear in the range from 5 kGy to 1 MGy for MTS
detectors. For both type of LiF detectors RPL signal is saturated for doses
higher than 100 kGy. The observed differences between MCP and MTS may suggest,
that the RPL effect in LiF is not entirely governed by intrinsic defects (F2
and F3+ centers), but impurities may also have a significant influence. Due to
the non-destructive character of the RPL measurement, it is suggested to apply
combined RPL/TL readouts, what should improve accuracy of high-dose dosimetry.
