Radiation Measurements 132 (2020) 106261 Available online 4 February 2020 1350-4487/© 2020 Elsevier Ltd. All rights reserved. PTTL characteristics of glass samples from mobile phones Michael Discher a, * , Clemens Woda b , Jungil Lee c , Hyoungtaek Kim c , Kisoo Chung d , Andreas Lang a a Paris-Lodron-University of Salzburg, Department of Geography and Geology, Salzburg, Austria b Helmholtz Zentrum München, Institute of Radiation Medicine, Neuherberg, Germany c Korea Atomic Energy Research Institute, Radiation Safety Management Division, Yuseong, Daejeon, Republic of Korea d Gyeongsang National University, Department of Physics, Jinju, Republic of Korea A R T I C L E INFO Keywords: PTTL Phototransferred thermoluminescence PTTL of display glass Dosimetric properties PTTL emission spectra Physical retrospective dosimetry ABSTRACT Phototransferred thermoluminescence (PTTL) of mobile phone display glass (category A) is systematically investigated to develop a robust measurement protocol for its emergency dosimeter usage after an incident with ionizing radiation. First, optimal readout parameters were defned by varying preheat temperature and holding time preceding violet exposure (405 nm). Next, the detection window of the PTTL measurement was adjusted to optimize the ratio between radiation-induced (RIS) and non-radiation-induced signals (nRIS) of the PTTL. Finally, the developed protocol determines PTTL after preheating to 400 � C and holding for 10 s was tested using the detection window centered at 340 nm. Dosimetric properties such as the PTTL reproducibility and dose response were investigated. PTTL signal stability tests showed that the violet PTTL signal originates from deeper and consequently more thermally stable traps. A signal loss of less than 10% after 10.6 days (254 h) storage was observed. Additionally, TL and PTTL spectra were recorded to investigate the luminescence emissions after beta and gamma irradiation and different UV exposures. PTTL emissions are similar to TL emission. Varying UV energy a qualitative comparison demonstrate that the RIS and nRIS PTTL signal intensities increase signifcantly with decreasing UV stimulation wavelength. In general, the developed PTTL protocol indicates better signal stability and thus some advantages over other techniques, however, further research is needed to test the po- tential of a new method for physical retrospective dosimetry. 1. Introduction Different investigations of retrospective dosimetry have shown that components of mobile phones are suitable as emergency dosimeters in case of radiological incidents. For physical dosimetry, components can be read out using optically stimulated luminescence (OSL), thermolu- minescence (TL) and phototransferred thermoluminescence (PTTL) methods to determine the absorbed dose. Among the variety of items investigated, a promising material is glass (i.e. watch glass, display glass, touch screen glass). Its dosimetric properties have been studied in detail for touch screen glasses (Chandler et al., 2019; McKeever et al., 2017; Discher et al., 2016) and display glasses of modern mobile phones (Kim et al., 2019; Bassinet et al., 2014; Discher and Woda, 2013, 2014; Mrozik et al., 2014). The studies show that a native signal, so-called zero dose signal, is observed for unexposed glass samples which signifcantly limits the low-dose sensitivity. Employing a labor-intensive sample preparation procedure can reduce the zero dose signal. Generally, the TL signal of glasses is also not stable over time and a fading correction has to be applied for an accurate dose reconstruction. The PTTL method uses deep radiation-sensitive traps for dose reconstruction and consists of (i) preheating the sample to a certain temperature, (ii) exposing the sample to UV/violet light and (iii) measuring the luminescence signal of electrons transferred to shallower traps, that were emptied during the preheating. In a recent investigation the PTTL signals of glasses from mobile phones were studied and indi- cated a higher thermal stability and therefore corrections for PTTL signal fading may not be needed (McKeever et al., 2017). 2. Materials and methods In this study representative glass samples of glass category A, ac- cording to the display glass classifcation in Discher and Woda (2013), were used which can be found in modern mobile phones (i.e. Nokia * Corresponding author. E-mail address: michael.discher@sbg.ac.at (M. Discher). Contents lists available at ScienceDirect Radiation Measurements journal homepage: http://www.elsevier.com/locate/radmeas https://doi.org/10.1016/j.radmeas.2020.106261 Received 30 October 2019; Received in revised form 22 January 2020; Accepted 3 February 2020