Using the different LET response of high and low temperature peaks in LiF:Mg,Ti for mixed neutron-gamma dosimetry – a controversial subject

The main high temperature peaks in the glow curves of LiF:Mg,Ti (assigned as 6 and 7), which appear at about 260 O C-270 O C, are known to have an enhanced response to higher LET radiation (as α particles) than to lower LET radiation (as photons). This effect can be used to discriminate between neutron and gamma radiations. In most works in the past a slow heating rate of up to ∼10C/s was employed for readout. However, in routine dosimetry a higher heating rate, normally about 25 O C/s, is used. The high rate heating causes a shift of the high temperature peaks towards 300 O C, which is also the limit when using TLD cards with Teflon coating of the chips. Thus, marginal conditions are present, which caused controversy on the justification of the experimental procedures. Besides, there are claims that the method may suffer from the non-constancy of the crystals impurity content and non-linearity of the peak 7 response to gamma dose. Published data is presented, along with new experimental results, leading to the conclusion that in spite of the technical constraints, the method has potential for mixed neutron-gamma dosimetry and further research efforts should be invested.