Retrospective dosimetry based on red Thermoluminescence (RTL) of a single resistor from mobile phones

In the framework of the European Project CONFIDENCE („COping with uNcertainties For Improved modelling and DEcision making in Nuclear emergenCiEs”), the dosimetric properties of alumina (Al 2 O 3 ) substrates of surface-mount resistors placed on mobile phone circuit boards were used to further develop a new retrospective dosimetry method. Resistors showed a strong emission due to the Cr 3+ emission at a wavelength of 695 nm, thus enabling Thermoluminescence (TL) measurements in the red detection window (RTL). The resulting strong increase in sensitivity, as compared to the earlier protocols in TL and OSL with either blue or UV light detection, allowed to establish a new protocol which is optimized for the low-dose region (10-100 mGy) and is based only on a single resistor. The single resistor can be potentially replaced, leaving the phone intact. Possible parameters affecting the precision of the method such as confounding signals intrinsic to the material (zero-dose), signal loss with time (anomalous fading), and uncertainty related to the instrumentation were explored. Irradiation trials on intact smartphones demonstrated that dose assessment down to 20 mGy and 40 mGy is possible at the single resistor level, for measurements up to several days and 30 days after exposure, respectively. • Further development of dosimetry method using red TL of resistors from mobile phones • Measurement protocol based on a single resistor and optimized for low dose region (10 – 100 mGy) • Identification of sources of uncertainties to improve the accuracy of the dose reconstruction