Use of OSL and TL of Electronic Components of Portable Devices for Retrospective Accident Dosimetry

Growing apprehensions of radiological accidents and terroristic attacks have intensified research efforts to find materials with appropriate radiation sensitivity that are carried close to human body, are ubiquitously available and which can be used as fortuitous dosimeters in rapid determination of doses of individuals after radiation exposure. In this respect, thermoluminescence (TL) and optically stimulated luminescence (OSL) of chip cards and electronic components of personal objects have been recently evaluated by researchers in several countries. OSL and TL signal of chip cards is attributed to SiO2 grains contained in the epoxy layers used for controlling the thixotropic properties whereas the radiation induced signal in electronic components (resistors, resonators, capacitors, ICs, antenna switches, etc.) of personal objects (mobile phones, USB flash drive, MP3 players, etc.) is attributed to the ceramic contents, especially to Al2O3 based substrates. Chip-cards exhibited large variations depending on the preparation process and some cards did not exhibit any measurable signal. Although, the radiation sensitive cards were found suitable for the estimation of dose from a few tens of mGy to tens of Gy with linear dose response, the variability of responses of cards from different origins/manufactures and the complexity of thermo-optical effects of the epoxy severely limits the use of chip-cards for accident dosimetry. For the electronic components of personal objects, TL and OSL properties such as zero-dose signal, TL glow peak structure and OSL nature of the substrates of different types of components varied considerably depending on its source. Among the studied components (resistors, resonators, ICs, capacitors, inductors, antenna switches etc.) of personal objects (mobile phones, USB flash drives, MP3 players etc.), the resistors of mobile phones with Al2O3 substrates exhibited higher OSL sensitivity (minimum measurable dose of about a few mGy), linear dose response up to several Gy, smaller sample to sample variation and higher reproducibility. Excessive anomalous fading for both TL and OSL signals was found to be the main hindrance. However, the trials of simulating the accidental exposures by fixing mobile phones and other devices on phantom, subjecting to irradiation in laboratory and by using the SAR protocol and fading corrections, were successful in evaluating the doses within about 10%. It is evident that the differences in the fading rates of the TL signals of glow peaks at different temperatures and different part of OSL curve and different types of readout procedures could provide important information of the exposures, including the elapsed time of an accident.