Accident dosimetry with mobile phones: Real-time measurements by means of mobile phone applications & Post-Accident dose reconstruction with SIM cards

In this work we investigate the use of smartphone applications to evaluate dose rates in case of incidents/accidents with ionizing radiation and the use of SIM cards for retrospective assessment of doses received by the public. The performance of the applications was tested in the calibration laboratory of SCK•CEN with 60Co and 137Cs sources and additional tests with X-rays were performed while the SIM cards were characterised by performing continuous wave optically stimulated luminescence (CW-OSL) measurements on several types of SIM cards using a TL/OSL Reader (Risø). The samples were irradiated with a 90Sr/90Y β- source and stimulated with blue LEDs inside the
Reader. The experiments showed that the apps have a long stabilisation time of at least 10 min and even longer for natural background levels. This clearly limits the use in emergencies. Also the Polismart PM1904, an add-on GM tube for smartphones, was tested. This dedicated detector exhibited a much lower stabilization time, more accurate readings and a better dose rate response.
Our SIM card tests showed a relative flat dose response up to 4 Gy and a significant difference in sensitivity between different cards. The OSL signals are reproducible within a deviation of about 10%. It was found that SIM cards can be used to reconstruct doses above 10 mGy. However, the strongest limitation is the fading of the OSL signal. Analysing a SIM card after a couple hours, a day or a few weeks will result in a signal drop of respectively 50%, 75% and 90%.