Ag-doped phosphate glass with high weathering resistance for RPL dosimeter

Ag-doped phosphate glass employed in the commercial dosimeter named FD-7 is used globally as one of the most reliable dosimeter materials. The luminescence phenomenon is well known as radiophotoluminescence (RPL). In this work, a new RPL glass material was developed for dosimeters that are used under high humidity conditions.

Radiation Measurements 140 (2021) 106492 Contents lists available at ScienceDirect Radiation Measurements journal homepage: http://www.elsevier.com/locate/radmeas Ag-doped phosphate glass with high weathering resistance for RPL dosimeter Masaru Iwao a, *, Hironori Takase a, Daiki Shiratori b, Daisuke Nakauchi b, Takumi Kato b, Noriaki Kawaguchi b, Takayuki Yanagida b a b Nippon Electric Glass Co., Ltd., 7-1, Seiran 2-Chome, Otsu-shi, Shiga, 520-8639, Japan Nara Institute of Science and Technology (NAIST), 8916-5 Takayama-cho, Ikoma-shi, Nara, 630-0192, Japan A R T I C L E I N F O A B S T R A C T Keywords: Radiophotoluminescence Glass dosimeter High weathering resistance Phosphate glass Ag-doped phosphate glass employed in the commercial dosimeter named FD-7 is used globally as one of the most reliable dosimeter materials The luminescence phenomenon is well known as radiophotoluminescence (RPL) In this work, a new RPL glass material was developed for dosimeters that are used under high humidity conditions The glass material that contains Ag2O as an activation center was produced by the melt-quenching method The radiation properties and the optimal amount of Ag2O concentration required for achieving the best performance of the glass were evaluated using the RPL read-out system employing the photon counting method On exposure to UV laser light radiation, the new RPL glass developed in this work emitted light of an approximate wavelength of 650 nm after radiation exposure, and the RPL intensity was proportional to the exposed dose In addition, the glass material exhibited high reusability owing to the repeated operation of irradiation and reset On conducting the weathering resistance test for a long duration, it was found that the new RPL glass exhibited the same RPL intensity and appearance as its initial values Introduction A larger variety of passive personal dosimeters are used in radiation control areas such as medical facilities, science laboratories, mining industry, and nuclear power plants These dosimeters are convenient for the end-users because of their low price, accuracy, shock resistance, and lack of electric power The number of dosimeter users is more than five million worldwide (Pradhan et al., 2016) The RPL dosimeter has many advantages over TLD, such as a small fading effect at room temperature (Lee et al., 2009), good dose linearity, and high reproducibility (Rano­ gajec-Komor et al., 2008) The mechanism of the luminescence phe­ nomenon by Ag ions in the RPL glass dosimeter and the luminescence process with build-up have been discussed by many researchers (Huang and Hsu, 2011; Miyamoto et al., 2011; McKeever et al., 2019; Kurobori et al., 2020; Sholom and Mckeever, 2020; Yamamoto et al., 2020) When the Ag-doped phosphate glass is irradiated by an ionizing radiation, electrons and holes are generated and the electrons are captured by Ag+ in the glass structure and become Ag0 However, holes are trapped in the PO4 tetrahedron, but migrate over time to Ag+, forming the more stable Ag2+ ions Ag2+ is the main RPL centers, shows the orange light under ultraviolet excitation light There is another possibility regarding the orange RPL centers that Ag+ diffuses to Ag0 to forms Ag+ Over fifty years, the RPL dosimeter named FD-7 glass (Yokota and Nakajima, 1965) has been produced using the same chemical compo­ sition as when it was first produced because of its high reliability However, abnormally luminescent signals derived from the surface degradation of the RPL glass have been reported by some researchers (Yamanishi et al., 2003; Hashimoto et al., 2004) This phenomenon is considered to occur when the surface degradation of the glass is accel­ erated by a high humidity environment In general, from the perspective of glass structure science, the phosphate glass network structure has poor weathering resistance, because the P–O–P bond (phosphate oxygen bond) is disconnected from the attack of OH− ions in the atmosphere (Bunker et al., 1984) To achieve a strong network structure of the phosphate glass, Al2O3, Fe2O3, and Pb2O3 are generally added (El-Deen et al., 2008; Lim et al., 2010; Weyl and Kreidl, 1941) Further, for improving the weathering resistance, in our previous study (Ikeda, 2019), it was found that by adding a small amount of SiO2 in phosphate * Corresponding author Development Division, Research and Development Group, Nippon Electric Glass Co., Ltd., 7-1, Seiran 2-Chome, Otsu -shi, Shiga, 5208639, Japan E-mail address: miwao@neg.co.jp (M Iwao) https://doi.org/10.1016/j.radmeas.2020.106492 Received 27 August 2020; Received in revised form 19 November 2020; Accepted 23 November 2020 Available online 30 November 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 M Iwao et al Radiation Measurements 140 (2021) 106492 glass, its surface appearance could be improved as compared to that of a phosphate glass without SiO2 The improvement in weather resistance by introducing SiO2 into phosphate glass was first reported by Izumitani (1998) It has also been reported that the weather resistance changes depending on the amount of SiO2 introduced It is presumed that when the amount of SiO2 introduced was small, the 6-fold coordinated Si crosslinked the network of the chain phosphate and the network became stronger, resulting in improved weather resistance On the other hand, when the introduction amount was further increased, the weather resistance decreased It was suggested that 4-fold coordinated Si enters as a tetrahedron between the tetrahedrons of PO4, breaking the chain of phosphoric acid and making phosphoric acid a single molecule Phos­ phoric acid is easily eluted by becoming a single molecule It is known by the study of Miyabe et al (2005) that the 6-fold coordination and 4-fold coordination of Si are actually formed by introducing SiO2 into phos­ phate glass using nuclear magnetic resonance (NMR) As it is important to increase the reliability of materials to conduct an accurate dosimetry, the aim of the present study was to develop a new glass material having a high weathering resistance for its use in an RPL dosimeter and investigate its radiation characteristics Furthermore, we established a read-out system for evaluating its luminescence decay time Experimental methods and materials 2.1 Experimental setup The RPL intensity was evaluated using an RPL read-out system that employs photon counting According to Nomura et al (2002), the luminescence in the FD-7 phosphate glass consists of three components: the luminescence due to the dirt on glass surface in a very short decay time region (of the order of ns), the RPL in the middle decay time region (a few μs), and a predose in the long decay time region having a low intensity The RPL intensity (the number of photons) obtained by inte­ grating the area of the decay curve in the range of 2–7 μs Thus, the RPL intensity of all glass samples was evaluated from the luminescence decay time using the RPL read-out system Here, the predose is the amount of light emitted by the sample itself before the radiation is irradiated It is the luminescence of the glass itself and is treated as the background before the measurement in this study Fig 1(a) shows the schematic of the RPL read-out system The light source used for the irradiation is an ultraviolet (UV) pulse laser having an excitation wavelength of 355 nm Fig (a) Schematic of the RPL read-out system (b) Luminescence observed from the 0.1Ag:PANS glass after γ-ray irradiation The orange line corresponds to the luminescence obtained from the glass excited by a UV laser M Iwao et al Radiation Measurements 140 (2021) 106492 Fig 1(b) shows a photograph of the light emitted from the glass sample in this study directly captured by a digital still camera Its emission spectrum is the same as Fig 5(a) shown later The pulsed laser was selected as a Q-switched solid-state laser con­ sisting of Nd:YAG Its pulse frequency and pulse width were set to 10 kHz and 10 ns Laser expose time was performed ms The average light power was set to 1.0 or 20 μW and monitored using a power meter (PD300R, Ophir) The average light power varied depending on the irradi­ ation dose In the case of predose and small dose evaluation, the average light power was set to 20 μW In contrast, a large dose evaluation was carried out using a small light power of 1.0 μW According to the study by Maki et al (2011), a laser beam with a significant amount of pulsed energy and repetition rate causes annealing of the RPL centers and un­ derestimates the radiation dose In this study, although a high repetition rate of the laser beam was used, the annealing effect did not occur The maximum pulsed energy was estimated to be 0.002 μJ, which is a very small value Thus, the laser beam condition did not affect the results of the intensity measurement Regarding the error of the RPL measure­ ment, the same sample was measured 10 times in this read-out system, consequently, the variation was ±3.5% The laser device was cooled with air fans to stabilize the optical laser power As shown in Fig 1(a), the laser beam entered perpendicularly in the central portion of the side of the glass sample, which was precisely positioned with a movable XYZ stage A photomultiplier tube (PMT, H10682-01, Hamamatsu Pho­ tonics), a photon counting board (M9003-01, Hamamatsu Photonics) as the photon counter, and a pulse delay generator (C10149, Hamamatsu Photonics) were connected to each other via signal cables and connected to a personal computer The RPL read-out process was as follows: The glass sample was irradiated by a pulsed ultraviolet laser, after which luminescence light was emitted from the glass sample The PMT detec­ ted the light emitted from the glass sample, and the photon counter counted the number of photons A UV band pass filter and long pass filter were placed in front of the laser source and the glass sample, respec­ tively This read-out system uses the UV cut filter to detect and monitor the luminescence lifetime for wavelengths above 560 nm with PMT The read-out system including the laser source, PMT, and sample stage was covered with a black almite box Orange light emitted from glass sam­ ples was observed after irradiating the samples with the UV laser light 2.3 Types of tests conducted and the instruments used To evaluate the absorption properties of the glass samples doped with different concentrations of Ag2O, their transmittance spectra were measured A spectrometer (V670, JASCO) was used for measuring the spectral range from 190 to 3000 nm with an interval of 0.1 nm The RPL emission was evaluated using a fluorescence spectrophotometer (F7000, Hitachi High-Tech Corporation) in the spectral range of 400–800 nm with an interval of 0.2 nm A UV cut filter was installed on the fluorescence spectrometer to prevent secondary light from the excitation source The spectra are corrected for the wavelength response of this detection system Subsequently, 137Cs γ-ray and X-ray radiation instruments were used for irradiating the glass samples The dosage of the samples irradiated by 137 Cs γ-ray was between 0.1 m and 20 Gy The following 137Cs γ-ray instruments were used The samples were irradiated in the range of 0.1–100 mGy using an original γ-ray irradiation instrument from the Nuclear Science Research Institute of Japan Atomic Energy Agency The samples were irradiated in the range of 1–20 Gy by PS-3200T (PONY INDUSTRY CO., LTD) at the Tokyo Metropolitan Industrial Technology Research Institute These irradiated samples were evaluated in terms of the following properties: linearity of the radiation response, RPL in­ tensity evaluation before and after the weathering resistance test, and repeated read-out X-ray irradiation of the prepared samples was carried out in the sensing device laboratory of the Nara Institute of Science and Technol­ ogy The dose amount was set at 1000 mGy The samples irradiated with X-rays were evaluated in a reusability test, i.e., the cyclic test of the generation of activation centers due to radiation exposure and the reset, i.e., the recombination of electron and hole due to annealing Further, the RPL intensity evaluation of the PANS glass containing different concentrations of Ag2O activator was carried out The preheating temperature required for accelerating the build-up and reset temperature corresponding to the disappearance of the acti­ vation centers in the Ag:PANS glass was estimated from the glass tran­ sition temperature (Tg) and corresponded to the same heating conditions of FD-7, as shown in previous studies (Kurobori, 2015, 2018) According to these studies, the preheat temperature and reset temperature were in the range of 70–100 ◦ C and 360–400 ◦ C, respectively Tg of the Ag:PANS glass and FD-7 composition glass measured using differential thermal analysis (DTA) were 514 ◦ C and 448 ◦ C, respectively, which are 66 ◦ C higher than that obtained for the FD-7 composition glass Based on these results and those from previous studies, the preheat temperature and reset temperature of the Ag:PANS glass was determined as follows The preheat temperature was set at 100 ◦ C for FD-7 composition glass and 160 ◦ C for Ag:PANS glass for 30 after irradiation The reset tem­ perature was set at 400 ◦ C for h for the FD-7 composition glass and 440 ◦ C for h for the Ag:PANS glass after irradiating them with 137Cs γ-ray and X-rays To evaluate the weathering resistance, the weathering resistance test was carried out at 40 ◦ C and 90% relative humidity in a constant tem­ perature and humidity chamber using deionized water This condition was referred to in the International Electrotechnical Commission stan­ dard (IEC 62387) The glass samples were taken out of the chamber after several days, and their luminescence was measured using the RPL readout system 2.2 Preparation of the new RPL glass samples The glass of the commercial FD-7 material has an atomic weight composition of 31.55% P, 51.16% O, 6.12% Al, 11.00% Na, and 0.17% Ag, and the effective atomic number and density are 12.04 and 2.61 g/ cm3, respectively (Kurobori, 2018) The oxide mol fraction of FD-7 composition converted form the above atomic weight composition is 59P2O5‒13.2Al2O3‒27.7Na2O‒0.1Ag2O In this study, a new glass with a composition of P2O5–Al2O3–Na2O–SiO2 (PANS) was developed by adding different concentrations (0.05, 0.1, 0.2, and 0.4 mol) of Ag2O as an activator SiO2 was added as it does not affect the visible transmission characteristics of the glass and helps in improving the weathering resistance Another way to improve the weathering resistance of phosphate glass is to increase the concentration of Al2O3 Therefore, the concentration of SiO2 and Al2O3 in the PANS glass were set to mol% and 19 mol%, respectively These Ag:PANS glass samples and FD-7 composition glass were prepared using the following procedure Reagent grade Na3PO4, AlPO4, SiO2, and Ag2O were mixed and melted at 1200 ◦ C in an electric furnace for h The melted glass was cooled rapidly in a carbon mold, and the glass ingots thus obtained were placed in an annealing furnace at approximately 500 ◦ C for h After annealing, the glass samples were cut into 30 × × mm3 pieces and polished using a grinding equip­ ment All glass samples were washed and cleaned using deionized water and ethanol solution before every evaluation Results and discussion Fig shows the typical decay curves, corresponding to the glass samples prepared in this study, obtained after their irradiation with 137 Cs γ-ray of 10 Gy As can be seen from the figure, the Ag:PANS glass has the same decay time as the FD-7 composition glass because it has almost the same composition and activator This indicates that the mechanism of RPL in the PANS glass is the same as that occurring in the FD-7 composition M Iwao et al Radiation Measurements 140 (2021) 106492 Fig Linear transmittance spectra of the as-melted glass samples having different Ag2O concentrations Inset is a partial expanded view of the range of 200–300 nm Fig Decay curves of the 0.1Ag:PANS glass (filled squares) and FD-7 composition glass (unfilled circles) excited at 355 nm using UV laser and monitored the luminescence above 560 nm after irradiation with 137Cs γ-ray of 10 Gy glass The decay curves for the samples before and after irradiation with 137 Cs γ-ray at a dose of mGy are shown in Fig It can be seen that there is a clear difference in the intensity before and after irradiation in the short decay time range from a few μs to 20 μs The density of the glass was measured using the Archimedes method with distilled water, and the density and effective atomic number of the PANS glass was 2.61 g/cm3 and 11.71, respectively These values are almost the same as those of FD-7 Therefore, it was assumed that the dependence of the response of the PANS glass on the radiation energy is close to that of FD-7 Fig shows the transmittance spectra of the Ag-doped PANS glass having different concentrations of Ag2O activator and FD-7 composition glass The transmittance spectra of all samples were as high as approx­ imately 90% in the visible range In the short-wavelength region (under 350 nm), the starting point of the absorption spectra was approximately 340 nm, and the absorption edge was between 219 and 236 nm It was found that this absorption edge shifted to a longer wavelength with increasing Ag2O concentration In the long-wavelength region, it was found that the transmittances decreased around 3000 nm This trans­ mittance decreasing is thought to be derived from the absorption due to Fig RPL spectra of 0.1Ag:PANS glass and FD-7 composition glass before and after irradiation with γ-rays of dose 20 Gy the presence of OH groups in the glass and the P–OH bond (Rai et al., 2011) Fig shows the luminescence spectra of the Ag:PANS glass emitted at 308 nm before and after γ-ray irradiation by employing a fluorescence spectrophotometer The samples irradiated with γ-rays of 20 Gy were evaluated for luminescence after preheating The excitation wavelength at 308 nm was used as the absorption peak derived from Ag2+ in phosphate glass (Kurobori et al., 2010) From the luminescence mea­ surement, the peak position of the luminescence intensity was obtained at 634 nm (emission in orange color) for the 0.1Ag:PANS glass This emission peak was also observed for the FD-7 composition glass This suggests that the mechanism of RPL in Ag:PANS glass is similar to that in the FD-7 composition glass This inference is also supported by the result that the Ag:PANS glass and FD-7 composition glass have almost the same main components and Ag concentration In addition, FD-7 composition glass was a little higher than 0.1Ag:PANS glass in the maximum peak intensity around 630 nm This intensity difference is unclear, however, as each sample contained the same Ag2O concentration, this result may be influenced by the composition ratio of the components of each glass sample Incidentally, the luminescence around 450 nm of samples before irradiation in Fig is the baseline noise peculiar to the device, not the peak caused by the sample It was observed without a sample Fig Decay curves of the non-irradiated samples (filled circles) and after 137 Cs γ-ray irradiation of dose mGy (unfilled circles) excited at 355 nm using UV laser and monitored the luminescence above 560 nm M Iwao et al Radiation Measurements 140 (2021) 106492 Fig shows the variation in the RPL intensity as a function of Ag2O concentration in the PANS glass The vertical axis of Fig shows the RPL intensity obtained by integrating the area of the decay curve in the range of 2–7 μs The decay curve is the intensity obtained by irradiating the excitation laser for 10 pulses at a repetition frequency of 10 kHz for each measurement, that is, the intensity integrated 10 times For a 0.1 mol% of Ag2O used in the PANS glass, the maximum intensity of RPL was observed at an irradiation of 1000 mGy As the Ag2O concentration increased beyond 0.1 mol%, the RPL intensity of the PANS glass was observed to decrease This result is identical to that obtained by Hsu et al (2010) In general, the decrease in the RPL intensity with increasing Ag2O concentration indicates the interaction with each activator This is called concentration quenching, in which the electrons interact with each other causing nonradiative transitions when the fluorescent centers are close to each other Fig shows the linearity of the dose response in the range 0.1 mGy–10 Gy for 0.1Ag:PANS glass The intensity of the luminescence is observed to increase depending on the irradiated dose A linear regres­ sion of the measurement and predicted values yielded an R2 of 0.99, indicating a reasonable agreement According to IEC 62387, a mea­ surement range of 0.1 mSv–1 Sv is required for a personal dosimeter The results show that the PANS glass is able to measure the radiation dosage in a range exceeding the required range in a personal dosimeter Fig shows the stability of the RPL intensity for the 0.1Ag:PANS glass sample obtained by repeated read-out Although the glass sample was stored at room temperature, without controlling the humidity and ambient light during the evaluation period, the RPL intensity showed the constant intensity for a long period This is equivalent to the stability of a commercial FD-7 glass As one of the characteristics of the RPL phenomena, it is suggested that the activation center is not affected by external environmental factors such as humidity, temperature, and excitation light Fig shows the relative RPL intensity values before and after the weathering resistance test In this test, evaluation of the 0.1Ag:PANS glass and FD-7 composition glass after their irradiation with γ-rays was conducted It was observed that 0.1Ag:PANS glass has a high weathering resistance because the RPL intensities were constant for a long period It has been suggested that the addition of SiO2 to the glass strongly con­ nects the P–O and Si–O bonds, and strengthens the glass structure frame against OH− attack In contrast, the FD-7 composition glass was observed to exhibit increasing luminescence after ten days of test The surface of the sample was observed to be covered with a sticky material soon after taking it out from the test chamber As the time elapsed, the Fig Relationship between the absorbed dose and RPL intensity for PANS glass containing 0.1 mol% of Ag2O concentration and irradiated with 137 Cs γ-ray Fig Stability of the RPL intensity in repeated read-out deviation in the measured values was observed to increase It is assumed that the surface degradation occurred owing to the elution of the phosphoric acid component in the FD-7 composition glass The increase in the RPL intensity indicates that the difference in the refractive indices at the phosphoric acid-air interface is smaller than the difference in the refractive indices at the original glass-air interface, which facilitates light extraction, and thus, increases the RPL intensity The RPL intensity of the FD-7 composition glass after 50 days in humidity test could not be evaluated due to bonding of the sample with a sticky material Fig 10 shows the appearance of the surfaces of the glass samples after the weathering resistance test The surface of the 0.1Ag:PANS glass was clear after the test, whereas the FD-7 composition glass exhibited dimming in a large area of the glass surface The dimming could have been caused by some compounds within the glass components coming into contact with moisture in the atmosphere This is because all ele­ ments, i.e., P, Na, and Al, were detected by the energy dispersive X-ray spectroscopy and particle precipitations of the order of a few μm were observed using an electron scanning microscope The result of this accelerated test suggests the possibility of inducing a dimming of the glass material of the conventional RPL dosimeter due to its wear under high humidity conditions for a long duration, similar to the internal Fig Relationship between Ag2O concentration and RPL intensity obtained from the PANS glass irradiated by an X-ray dose of 1000 mGy M Iwao et al Radiation Measurements 140 (2021) 106492 Fig Relative RPL intensity before and after the weathering resistance test The filled circles correspond to 0.1Ag:PANS glass, whereas the unfilled triangles correspond to FD-7 composition glass Fig 11 The RPL intensity of 0.1Ag:PANS glass (orange dot) and FD-7 glass (gray dot) integrating emission from 500 nm to 800 nm upon 310 nm excitation as a function of elapsed time energy level of holes trapping due to defects in the glass structure derived from the introduction of Si has changed We think that the relevance of these phenomena needs further investigations and have room for investigation and discussion on the Si coordination number and the RPL process of this glass by NMR and ESR measurements since there are no reports investigating the state of structure defects due to Si introduced into the phosphate glass The reusability of 0.1Ag:PANS glass was evaluated by repeating the cycle of generation and elimination of the Ag activation centers The evaluation was carried out for measuring the RPL intensity after varying the dose of the X-ray irradiation and the predose intensity after heating The heating conditions of the preheat for build-up and the reset to evaluate the RPL and the predose were set at 160 ◦ C for 30 and at 450 ◦ C for h, respectively The result of the reusability test is shown in Fig 12 After ten cycles, no changes in the RPL intensity and the predose intensity were observed regardless of the irradiated dose The stable measurement results obtained from the reusability test indicate the following In the case of a glass element having a low weathering Fig 10 Appearance of the glass samples after 50 h in the weathering resis­ tance test The left sample is the Ag-doped PANS glass, whereas the right sample is the FD-7 composition glass condition of the radiation protective clothing Currently, the rule of radiation exposure measurement established in each country is at most four months It can be inferred that the reliability can be sufficiently ensured even if this PANS glass is worn for h a day Regarding Ag:PANS glass, The addition of SiO2 and the increase in Al2O3 in the glass increased Tg and improved weathering resistance It was also confirmed that the preheat temperature for build-up also rises compared to FD-7 In addition, Fig 11 shows the change in the RPL intensity of 0.1Ag:PANS glass and FD-7 glass derived from Ag2+ after irradiation, namely build-up curve These glass samples were irradiated with X-rays of 10 Gy, and the RPL excited at 310 nm as a function of elapsed time was evaluated on the emission from 500 nm to 800 nm with a fluorescence spectrophotometer (FP-8600, JASCO) at room tempera­ ture The RPL intensity of 0.1Ag:PANS glass increased immediately after the irradiation and continued to increase even after 14 h Meanwhile, that of FD-7 glass showed a constant value after h The result was similar to that of Miyamoto et al (2010) It was found that the build-up time of 0.1Ag:PANS glass was longer than that of FD-7 glass From these results, it is suggested that the presence of Si and Al in the phosphate glass, which improves weathering resistance, not only strengthened the network of the phosphate glass, but also increased the energy barrier for the diffusion of Ag ions Furthermore, there is a possibility that the Fig 12 Result of the RPL intensity (filled circle) and predose intensity (filled triangle) of the 0.1Ag:PANS glass obtained from the reusability test at the irradiation dose of 1000 mGy M Iwao et al Radiation Measurements 140 (2021) 106492 resistance, a structural change in the host glass material will occur during its long-term use Furthermore, as cycles of exposures/resets are repeated, the electrons and holes generated by ionization are trapped in the defects of the changed glass structure There is a possibility that the RPL intensity and predose intensity will exhibit values different from the initial ones obtained for the glass having a low weathering resistance In this study, 0.1Ag:PANS glass was exposed to tens to thousands of times of actual radiation dose, and this operation was repeated ten times The reason for setting this condition was that the number and the amount of repeated valence changes for Ag ions in the glass are considered to affect the number of reuses In other words, these changes are reflected in the RPL and predose intensities The result in Fig 12 shows that the elec­ trons and holes generated by the incident radiation completely formed the activation centers of Ag even after repeated irradiation/reset, because the variation in RPL intensity was not observed This suggests that the use of PANS glass as a dosimeter element can be expected to prolong the lifetime of the individual/environmental dosimeters Hashimoto, T., Hashimoto, M., Ishikawa, M., Emori, S., 2004 Investigation on the performance of dosimeters for individual monitoring applications at the O-arai engineering center (in Japanese) Hoken Butsuri 39 (3), 231‒237 https://doi.org/ 10.5453/jhps.39.231 Hsu, S.M., Yan, H.W., Huang, Y.H., Lee, J.H., Yu, C.Y., Liao, Y.J., Hung, S.K., Lee, M.S., 2010 Chemical and physical characteristics of self-fabricated radiophotoluminescent glass dosimeter Radiat Meas 45, 553–555 https://doi.org/ 10.1016/j.radmeas.2009.11.045 Huang, D.Y.C., Hsu, S.M., 2011 Radio-photoluminescence glass dosimeter (RPLGD) In: Gali-Muhtasib, Hala (Ed.), Advances in Cancer Therapy InTech Open, pp 553–568 https://doi.org/10.5772/23710 Ikeda, H., 2019 Structure and weathering of SiO2 contained phosphate glass In: 25th International Congress on Glass, in Oral Presentation, ICG-SI-143-2019 The American ceramics society Izumitani, T., 1998 Kougaku garasu to re-za garasu (in Japanese) Nikkan kogyo shinbunshya, pp 132–133 Kurobori, T., Wahng, Z., Miyamoto, Y., Nanto, H., Yamamoto, T., 2010 The role of silver in the radiophotoluminescent properties in silver-activated phosphate glass and sodium chloride crystal Opt Mater 32, 1231‒1236 https://doi.org/10.1016/j optmat.2010.04.004 Kurobori, T., 2015 A glass imaging detector (in Japanese) FBNews 467, 1–5 http s://www.c-technol.co.jp/cms/wp-content/uploads/2014/04/FBN467_web.pdf (accessed 14 July 2020) Kurobori, T., 2018 Performance characterization of a real-time fiber dosimetry system using radiophotoluminescent glasses Jpn J Appl Phys 57, 106402 https://doi org/10.7567/JJAP.57.106402 Kurobori, T., Kada, W., Yanagida, Y., Koguchi, Y., Yamamoto, T., 2020 Variable periodic time operated fibre-coupled dosimetry system using Ag-activated RPL glasses with build-up Radiat Meas 133, 106300 https://doi.org/10.1016/j radmeas.2020.106300 Lee, J.H., Lin, M.S., Hsu, S.M., Chen, I.J., Chen, W.L., Wang, C.F., 2009 Dosimetry characteristics and performance comparisons: environmental radiophotoluminescent glass dosemeters versus thermoluminescent dosemeters Radiat Meas 44, 86‒91 https://doi.org/10.1016/j.radmeas.2008.10.013 Lim, J.W., Schmitt, M.L., Brow, R.K., Yung, S.W., 2010 Properties and structures of tin borophosphate glasses J Non-Cryst Solids 356, 1379‒1384 https://doi.org/ 10.1016/j.jnoncrysol.2010.02.019 Maki, D., Sato, F., Kato, Y., Yamamoto, T., Iida, T., 2011 Improvement of a dose reading system for radiophotoluminescence glass dosimeters Radioisotopes 60, 55‒61 https://doi.org/10.3769/radioisotopes.60.55 McKeever, S.W.S., Sholom, S., Shrestha, N., 2019 Observations regarding the build-up effect in radiophotoluminescene of silver-doped phosphate glasses Radiat Meas 123, 13–20 https://doi.org/10.1016/j.radmeas.2019.02.009 Miyabe, D., Takahashi, M., Tokuda, Y., Yoko, T., Uchino, T., 2005 Structure and formation mechanism of six-fold coordinated silicon in phosphosilicate glasses Phys Rev B 71, 172202 https://doi.org/10.1103/PhysRevB.71.172202 Miyamoto, Y., Yamamoto, T., Kinoshita, K., Koyama, S., Takei, Y., Nanto, H., Shimotsuma, Y., Sakakura, M., Miura, K., Hirao, K., 2010 Emission mechanism of radiophotoluminescence in Ag-doped phosphate glass Radiat Meas 45, 546–549 https://doi.org/10.1016/j.radmeas.2010.01.012 Miyamoto, Y., Takei, Y., Nanto, H., Kurobori, T., Konnai, A., Yanagida, T., Yoshikawa, A., Shimotsuma, Y., Sakakura, M., Miura, K., Hirano, K., Nagashima, Y., Yamamoto, T., 2011 Radiophotoluminescence from silver-doped phosphate glass Radiat Meas 46, 1480–1483 https://doi.org/10.1016/j.radmeas.2011.05.048 Nomura, K., Ikegami, T., Juto, N., 2002 Development of dosimeters for personal monitoring I Radiophoto-luminescent glass dosimeter (in Japanese) Radioisotopes 51, 85‒95 https://doi.org/10.3769/radioisotopes.51.85 Pradhan, A.S., Lee, J.I., Kim, J.L., 2016 On the scenario of passive dosimeters in personnel monitoring: relevance to diagnostic radiology and fluoroscopy-based interventional cardiology J Med Phys 41 (2), 81–84 https://doi.org/10.4103/ 0971-6203.181634 Rai, V.N., Sekhar, B.N.R., Tiwari, P., Kshirsagar, R.J., Deb, S.K., 2011 Spectroscopic studies of gamma irradiated Nd doped phosphate glasses J Non-Cryst Solids 357, 3757–3764 https://doi.org/10.1016/j.jnoncrysol.2011.07.036 ˇ Miljani´c, S., Veki´c, B., 2008 Characterisation of Ranogajec-Komor, M., Kneˇzevi´c, Z., radiophotoluminescent dosimeters for environmental monitoring Radiat Meas 43, 392‒396 https://doi.org/10.1016/j.radmeas.2007.11.020 Sholom, S., McKeever, S.W.S., 2020 High-dose dosimetry with Ag-doped phosphate glass: applicability test with different techniques Radiat Meas 132, 106263 https://doi.org/10.1016/j.radmeas.2020.106263 Weyl, W.A., Kreidl, N.J., 1941 Phosphates in ceramic ware: IV, Phosphate glasses J Am Ceram Soc 24, 372–378 https://doi.org/10.1111/j.1151-2916.1941.tb14816.x Yamamoto, T., Yanagida-Miyamoto, Y., Iida, T., Nanto, H., 2020 Current status and future prospect of RPL glass Radiat Meas 136, 106363 https://doi.org/10.1016/j radmeas.2020.106363 Yamanishi, H., Miyaka, H., Yamasaki, T., Komura, K., 2003 Self dose of TLD and radiophoto-luminescence glass dosimeter measured in Ogoya tunnel (in Japanese) Hoken Butsuri 38 (1), 45–49 https://doi.org/10.5453/jhps.38.45 Yokota, R., Nakajima, S., 1965 Improved fluoroglass dosimeter as personnel monitoring dosimeter and microdosimeter Health Phys 11 (4), 241–253 https://doi.org/ 10.1097/00004032-196504000-00001 Conclusion A new RPL glass material, namely Ag:PANS glass, was developed in this work for its use in a radiation dosimeter The following character­ istics have been observed from the tests conducted on it As compared to the conventional dosimeter material, namely, the FD-7 composition glass, the weathering resistance property of Ag:PANS glass was observed to be much superior In addition, the RPL characteristics of the devel­ oped glass were found to be equivalent to that of the FD-7 composition glass This implies that Ag:PANS glass can be used in harsher environ­ ments, e.g., in hot and humid areas, or harsh working conditions Since the surface turbidity of the glass does not occur under high humidity, the possibility of showing an abnormal value is reduced, its high reusability can also contribute to improving the reusability rate of monitoring service This dosimeter material has many applications apart from its use in personal/environmental dosimeters For example, it can be used in medical applications for surgical operations, because it can be produced in different forms such as fibers, thin plates, and rings owing to the advantage of the high degree of freedom of molding glass Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper Acknowledgements The authors thank H Takeuchi, M Kadomi and H Ikeda of Nippon Electric Glass Co., Ltd for their support and useful discussions in this work References Bunker, B.C., Arnold, G.W., Wilder, J.A., 1984 Phosphate glass dissolution in aqueous solutions J Non-Cryst Solids 64, 291‒316 https://doi.org/10.1016/0022-3093 (84)90184-4 El Deen, L.M.S., Al Salhi, M.S., Elkholy, M.M., 2008 Spectral properties of PbO–P2O5 glasses J Non-Cryst Solids 354, 3762–3766 https://doi.org/10.1016/j jnoncrysol.2008.03.032 ... 100 ◦ C for FD-7 composition glass and 160 ◦ C for Ag:PANS glass for 30 after irradiation The reset tem­ perature was set at 400 ◦ C for h for the FD-7 composition glass and 440 ◦ C for h for the... develop a new glass material having a high weathering resistance for its use in an RPL dosimeter and investigate its radiation characteristics Furthermore, we established a read-out system for evaluating... characteristics of the glass and helps in improving the weathering resistance Another way to improve the weathering resistance of phosphate glass is to increase the concentration of Al2O3 Therefore, the concentration