Mitigation of the proton-induced low temperature anomaly of LiF:Mg,Cu,P detectors using a post-irradiation pre-readout thermal protocol

Abstract

7LiF:Mg,Cu,P (MCP-7) thermoluminescent detectors were exposed at nine positions within a 60 MeV pristine proton Bragg peak to investigate the possibility of counteracting the occurrence of their low temperature anomalous behavior (strong increase in the relative intensity of the peak 3 after exposure to energetic charged particles, Parisi et al., 2018 a) by using the post-irradiation pre-readout thermal protocol of 120 °C for 30 min. Simulations with the Monte Carlo radiation transport code PHITS were performed in order to determine the absorbed dose, the LET and the specific energy density distributions within the detector volume as a function of its position along the Bragg peak. The experimentally determined efficiency values for the main peak signal agreed with the results of the Microdosimetric d(z) Model with an average deviation of 2.4%. The consistency of the results supports the hypothesis that the light signal of the main peak 4 partly arises from trapped charge carriers previously giving rise to the neighboring low-temperature peak 3 and that the non-standardized post-irradiation procedure is the reason for the spread in the experimentally determined proton efficiency data present in literature. Thus, for a correct dose assessment and to mitigate possible low temperature anomalies in the glow curve structure of LiF:Mg,Cu,P detectors, it is strongly advised to always employ the recommended preheat protocol of 30 min at 120 °C.