The objective of this study was to investigate the energy and angle dependence of the RPL dosimetry system in use at the Paul Scherrer Institute (GBFJ-01 dosimeter, FGD 660 reader, and CDEC-Easy algorithm) for the operational dose quantity H*(10) and compare the results with the requirements from the Swiss dosimetry regulation.
Radiation Measurements 138 (2020) 106468 Contents lists available at ScienceDirect Radiation Measurements journal homepage: http://www.elsevier.com/locate/radmeas Dosimetric properties of an environmental H*(10) dosemeter based on radiophotoluminescence of silver doped phosphate glass Frank Assenmacher, Elisa Musto, Eduardo G Yukihara * Department of Radiation Safety and Security, Paul Scherrer Institute, Switzerland A R T I C L E I N F O A B S T R A C T Keywords: Radiophotoluminescence RPL Environmental dosimetry H*(10) IEC 62387 Type testing The objective of this study was to investigate the energy and angle dependence of the RPL dosimetry system in use at the Paul Scherrer Institute (GBFJ-01 dosimeter, FGD 660 reader, and CDEC-Easy algorithm) for the operational dose quantity H*(10) and compare the results with the requirements from the Swiss dosimetry regulation The energy response was determined for photon energies between 12 keV (N-15) and 1250 keV (60Co) and the angle response was determined for 65 keV (N-80) and 662 keV (137Cs) The data obtained in this study show that the RPL dosimeters satisfy the requirements of the Swiss dosimetry regulation for the energy dependence, but only partially satisfy the requirements for the angle dependence For directional irradiations around ±90◦ the dosimeter response can deviate by more than the 20% allowed by the Swiss dosimetry regu lation If a more realistic testing scenario for the 90◦ irradiation is used, which includes full rotation of the dosimeter around its reference direction, the response is within 10% of the response at 0◦ irradiation Full tests according to the IEC 62387 were not performed and, therefore, performance against this standard cannot be fully evaluated from this data Nevertheless, the data indicate that the asymmetric dosimeter design would have difficulties satisfying the IEC 62387 standard for H*(10) for low energy photons and large angle irradiation, in spite of the allowance of full rotation for the 90◦ irradiations Introduction The radiophotoluminescence (RPL) of silver-doped phosphate glass (P4O10:Ag+), which is the UV-excited photoluminescence from color centers (Ag0, and Ag2+) created in the glass by ionizing radiation, is now used commercially for personal dosimetry (Kurobori et al., 2010; Miyamoto et al., 2010, 2011; Yamamoto et al., 2011) These color centers are stable under optical excitation and not fade over time, making the readout non-destructive Annealing of the glass detectors (e g 400 ◦ C for h) restores the original silver dopant (Ag+) concentration, allowing the material to be used again with the same response (Yama moto et al., 2011) The silver-doped phosphate glass is an integrating, passive solid-state detector, which, combined with filters for ionizing radiation, a dose calculation algorithm and automated readers, can be used for the measurement of the personal dose equivalent quantities Hp(10) and Hp(0.07), or of the environmental dose equivalent H*(10) (Burgkhardt et al., 1990; Piesch and Burgkhardt, 1994; Juto, 2002; Ranogajec-Komor et al., 2008) A modern RPL dosimetry system consisting of a dosimeter badge containing a silver-phosphate glass and different filters, auto mated reader and a dose calculation algorithm for personal and envi ronmental dosimetry is now commercialized by CHIYODA TECHNOL CORP In 2016 the Paul Scherrer Institute (PSI) adopted for individual monitoring of its staff the RPL system consisting of the GBFJ-01 dose meter badge version and FGD-660 reader (CHIYODA TECHNOL CORP.) This system was first used in 2008 at the Institut de Radioprotection et de Sûret´e Nucl´eaire (IRSN, France) in their routine dosimetry service (Hocine et al., 2011; Hocine, 2012) The dosemeter badge has di mensions 61.0 × 30.0 × 8.0 mm3 and contains a RPL glass detector of dimensions 35.0 × 7.0 × 1.5 mm3 and filters made from aluminum, copper, tin, and two kinds of plastic materials, forming five differently filtered areas of the glass detector; for details, see Hocine et al (2011) The detector material FD-7 was produced by AGC TECHNO GLASS CO., LTD., Shizuoka, with a weight composition of 31.55% P, 51.16% O, 6.12% Al, 11% Na, and 0.17% Ag resulting in Ag+-doped phosphate glass (P4O10: Ag+) (Yamamoto et al., 2011) The FGD-660 reader mea sures each glass detector in five distinct positions, corresponding to the * Corresponding author Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland E-mail address: Eduardo.Yukihara@psi.ch (E.G Yukihara) https://doi.org/10.1016/j.radmeas.2020.106468 Received 12 May 2020; Received in revised form 14 August 2020; Accepted 16 September 2020 Available online 19 September 2020 1350-4487/© 2020 The Authors Published by Elsevier Ltd This is an open (http://creativecommons.org/licenses/by-nc-nd/4.0/) access article under the CC BY-NC-ND license F Assenmacher et al Radiation Measurements 138 (2020) 106468 five differently filtered areas in the dosemeter badge; see Huang and Hsu (2011) for an illustration of the measurement principle The dosimetric properties of this system for Hp(10) and Hp(0.07) were reported by Assenmacher et al (2017) and demonstrated to satisfy the Swiss dosimetry regulation for personal dosimeters The updated Swiss dosimetry regulation in effect since 2018 intro duced requirements for environmental dosimeters to be used in Switzerland (Swiss Federal Council, 2017) Requirements for H*(10) are specified for the measurement range (from 0.05 mSv up to 100 mSv), linearity (