Characterization of thermoluminescence of chip cards for emergency dosimetry

https://doi.org/10.1016/j.radmeas.2020.106321Get rights and content

Highlights

  • Different model of chip cards were investigated for emergency dosimetry.

  • Different weight percent of silica was found depending on chip cards.

  • Blue or red emissions was measured depending on chip cards through different combinations of optical filters.

Abstract

The thermoluminescence of different chip cards was measured and analyzed for emergency dosimetry. Three SIM cards that are commonly found in mobile communication providers in South Korea and three smart IC cards that can be purchased online were used for the experiment. Chemical element analysis based on EDS mapping images was carried out and different weight percent of silica was found for each chip card. Glow curves of radiation induced signals through different combinations of optical filters showed blue or red emissions depending on chip cards. Sensitivity change resulting from the thermal stimulation was found to be 1.8 ± 0.27 and 0.5 ± 0.06 for the blue and red emission, respectively. In addition, signal fading resulted in more than 20% of the initial signal remaining 20 days after irradiation, when the 100–150 °C signal is used. Furthermore, the dose response was recorded from 50 mGy to 10 Gy for each chip card.

Introduction

Thermoluminescence (TL) and optically stimulated luminescence (OSL) methods using mobile phone components such as substrate or cover glass, surface mount resistors and integrated circuits have been widely studied for emergency dosimetry (Discher and Woda, 2013; Lee et al., 2015; Sholom and McKeever, 2016). However, these materials are accompanied with labor intensive pretreatment processes, such as sample extraction, washing, and etching, which is a bottleneck for rapid triage in case of radiation accidents or terrorism. Chip card modules are widely used in electronic authorization applications like subscriber identification module (SIM) cards, identity cards, credit cards, and public transit. As such, chip cards are suitable for an individual dose reconstruction in a mass casualty scenario with easy extraction and no pretreatment processes (Göksu, 2003; Mathur et al., 2007; Woda and Spöttl, 2009) and being an item of low replacement cost compared to mobile phones. In a previous study a minimum detectable dose of several tens of mGy was found for chip cards when using OSL, however, the signal loss was over 60% in the first day after irradiation because the recommended protocol did not include a preheat (Woda and Spöttl, 2009). Fading can be significantly reduced for chip card modules with molded encapsulations but the protocol requires a chemical pretreatment with HNO3 (Woda et al., 2012).

TL of chip cards has so far not been used for dose reconstruction due to an intense zero-dose signal, which is the dominant feature in the higher temperature range of the glow curve. Moreover, signal regeneration can be observed when samples are preheated, for instance 100 °C for 10s, possibly caused by the slower reduction rate of the 100 °C TL peak on optical stimulation (Woda and Spöttl, 2009). Nevertheless, TL of chip cards has the potential of enabling better protocols such as an optimized detection window, inferred from TL emission spectra, a lower fading rate when using deeper (higher temperature) traps, and categorization of chip cards based on glow curves. Therefore, in this study, the TL characteristics of different types of chip cards were investigated to determine the limits and potentials of the TL protocols for emergency dosimetry.

Section snippets

Materials and methods

Since types of chip cards that exhibit a radiation response in OSL are limited depending on the manufacture and technology (Bassinet et al., 2010), a good candidate should be identifiable by the manufacturer and have a high radiation response. Therefore, chip cards used in this study were three SIM cards distributed by mobile communication providers in South Korea such as SK Telecom (SKT), Korea Telecom (KT), and LG Telecom (LGT). In addition, three smart Integrated Circuit (IC) cards that can

Results and discussions

TL of chip cards is mainly originated from the silica (SiO2) in the epoxy (Woda and Spöttl, 2009; Woda et al., 2012). In order to confirm the difference in the silica content depending on the chip cards, the EDS analysis was made in Fig. 2. The pictures in the first line in Fig. 2 are SEM images. The second line shows EDS mapping images for silicon and the third line is ones for oxide. Elements other than carbon, oxide, aluminum and silicon were less than 0.1% in weight percent. The width of

Conclusions

Feasibility and limitation of the TL protocol of chip cards for retrospective dosimetry were investigated. The chip cards showed different shape of the intrinsic background signals depending on the manufacturers but can be categorized by emission spectra of RISs. The red emission chip cards were not suitable for a dose estimation due to their unstable signals. On the other hand, a lower and less scattered signal fading was observed in the blue emission chip cards when 100–150 °C interval is

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 study was mainly carried out under the National Long- & Intermediate-Term Project of Nuclear Energy Development of Ministry of Science and ICT, Republic of Korea (No.2017M2A8A4015255) and is partially conducted in the framework of EPU (Eurasia-Pacific UNINET) network and partially funded by funds of the Federal Ministry of Science, Research and Economy (BMWFW) Austria (project period: 2019).

References (8)

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