The potential of luminescence signals from electronic components for accident dosimetry

On the Applicability of Camera Lens Protectors in Emergency Luminescence Dosimetry

In this work, the optically stimulated luminescence (OSL) properties of camera lens protectors and their potential use in emergency dosimetry were investigated. Camera lens protectors can be attached to mobile phones, which are commonly carried by individuals and may be useful in estimating an emergency dose. The presented results confirm the great potential of this type of glass material for dose determination. The glass protectors exhibit advantageous properties, such as linear dose dependence in the range of at least 0.6-10 Gy, minimum detectable dose at the level of tens of mGy, and good measurement repeatability for samples of the same type. Significant fading during the first day after exposure is an undesirable feature of tested glass. Nevertheless, the application of the correction for fading shows promising results in the dose recovery process.

DEVELOPMENTS IN THE USE OF THERMOLUMINESCENCE AND OPTICALLY STIMULATED LUMINESCENCE FROM MOBILE PHONES IN EMERGENCY DOSIMETRY

Proposed physical dosimetry methods for emergency dosimetry in radiological, mass-casualty incidents include both thermoluminescence (TL) and optically stimulated luminescence (OSL). Potential materials that could feasibly be used for TL and OSL dosimetry include clothing, shoes and personal accessories. However, the most popular target of study has been personal electronics, especially different components from smartphones. Smartphones have been a focus because they are widely available and, in principle, may be viewed as surrogates for commercial TL or OSL dosimeters. The components of smartphones that have been studied include surface mount devices (such as resistors, capacitors and inductors) and glass materials, including front protective glass, display glass and (with more modern devices) back protective glass. This paper reviews the most recent developments in the use of TL and OSL with these materials and guides the way to future, and urgently needed, research.

Use of commercial pharmaceutical drug (Daktarin®) for retrospective/accidental/forensic thermoluminescence dosimetry

Retrospective/accidental dosimetry seeks for materials that can be used as probes for the dose assessment by means of several methods when there is no dose data available (e.g. from personal dosimeters). In the same respect, researchers also seek materials appropriate for forensic purposes, which would allow to identify the prior presence of radioactive materials at buildings, sites or even vehicles. To this direction, several solid-state drugs, which are ubiquitous, have also been studied as probes for the dose estimation in emergency situations. However, due to their heat-sensitive character, measurements were possible only with OSL. The scope of the present work is to identify a heat-resistant drug (Daktarin) and conduct, for the first time, a detailed study of the thermoluminescence properties of it along with computerized curve deconvolution analysis which would shed light on the traps involved. Results indicate that the glow curve of Daktarin has at least three peaks that can be used for dosimetric purposes, since they exhibit linear dose response for doses up to 20 Gy, do not exhibit any sensitization, have high lifetime and their stability with time is good, since an appreciable signal remains unaffected even 3 months post irradiation. All the above were validated conducting dose recovery tests and successfully calculating the unknown delivered dose for various periods after the irradiation of the samples. The new findings are very supportive and point towards the efficient use of commercial pharmaceuticals as probes for retrospective/accidental/forensic dosimetry using thermoluminescence.

Optically stimulated luminescence (OSL) dosimetry in irradiated alumina substrates from mobile phone resistors

In this study the dosimetric properties of alumina (Al₂O₃) substrates found in resistors retrieved from mobile phones were investigated. Measurements of the decline of optically stimulated luminescence (OSL) generated following exposure of these substrates to ionising radiation showed that 16% of the signal could still be detected after 2 years (735 days). Further, the magnitude of the regenerative dose (calibration dose; D _i) had no impact on the accuracy of dose estimates. Therefore, it is recommended that the D _i be set as low as is practicable, so as to accelerate data retrieval. The critical dose, D _CL, and dose limit of detection, D _DL, taking into account the uncertainty in the dose-response relation as well as the uncertainty in the background signal, was estimated to be 7 and 13 mGy, respectively, 1 h after exposure. It is concluded that given the significant long-term component of fading, an absorbed dose of 0.5 Gy might still be detectable up to 6 years after the exposure. Thus, OSL from alumina substrates can be used for dosimetry for time periods far in excess of those previously thought.

Emergency EPR and OSL dosimetry with table vitamins and minerals

Several table vitamins, minerals and L-lysine amino acid have been preliminarily tested as potential emergency dosemeters using electron paramagnetic resonance (EPR) and optically stimulated luminescence (OSL) techniques. Radiation-induced EPR signals were detected in samples of vitamin B2 and L-lysine while samples of multivitamins of different brands as well as mineral Mg demonstrated prominent OSL signals after exposure to ionizing radiation doses. Basic dosimetric properties of the radiation-sensitive substances were studied, namely dose response, fading of the EPR or OSL signals and values of minimum measurable doses (MMDs). For EPR-sensitive samples, the EPR signal is converted into units of dose using a linear dose response and correcting for fading using the measured fading dependence. For OSL-sensitive materials, a multi-aliquot, enhanced-temperature protocol was developed to avoid the problem of sample sensitization and to minimize the influence of signal fading. The sample dose in this case is also evaluated using the dose response and fading curves. MMDs of the EPR-sensitive samples were below 2 Gy while those of the OSL-sensitive materials were below 500 mGy as long as the samples are analyzed within 1 week after exposure.

INTEGRATED CIRCUITS FROM MOBILE PHONES AS POSSIBLE EMERGENCY OSL/TL DOSIMETERS

In this article, optically stimulated luminescence (OSL) data are presented from integrated circuits (ICs) extracted from mobile phones. The purpose is to evaluate the potential of using OSL from components in personal electronic devices such as smart phones as a means of emergency dosimetry in the event of a large-scale radiological incident. ICs were extracted from five different makes and models of mobile phone. Sample preparation procedures are described, and OSL from the IC samples following irradiation using a (90)Sr/(90)Y source is presented. Repeatability, sensitivity, dose responses, minimum measureable doses, stability and fading data were examined and are described. A protocol for measuring absorbed dose is presented, and it was concluded that OSL from these components is a viable method for assessing dose in the days following a radiological incident.

Characterization of natural and irradiated nails by means of the depolarization metrics

Mueller polarimetry is applied to study the samples of nails: natural (or reference) and irradiated to 2 Gy ionizing radiation dose. We measure the whole Mueller matrices of the samples as a function of the scattering angle at a wavelength of 632.8 nm. We apply depolarization analysis to measured Mueller matrices by calculating the depolarization metrics [depolarization index, Q(M)-metric, first and second Lorenz indices, Cloude and Lorenz entropy] to quantify separability of the different samples of nails under study based on differences in their Mueller matrix. The results show that nail samples strongly depolarize the output light in backscattering, and irradiation in all cases results in increasing of depolarization. Most sensitive among depolarization metrics are the Lorenz entropy and Q(M)-metric.

Luminescence-based retrospective dosimetry using Al2O3 from mobile phones: a simulation approach to determine the effects of position

Monte Carlo modelling has been performed in support of efforts to establish emergency dosimetry services based on optically or thermally stimulated luminescence (OSL/TL) of the Al(2)O(3) substrate present on the resistors found in mobile phones, which can act as fortuitous retrospective dosemeters for photon exposures. Specifically, a range of exposure conditions has been modelled to assess the dependence of the dosimetry on factors such as the position of resistors within a phone, the orientation of the phone relative to the source, and the location of the phone relative to its owner. Variations due to the resistors' positions and the phone's orientation were generally found to contribute just a few percent to the uncertainty on the dose assessments, though the electrical contacts surrounding the resistors could potentially enhance these by several 10s of percent. But, the location of the phone was found to impact dosimetry greatly. The largest discrepancies in the results were found for low-energy exposures: for (192)Ir, differences of up to an order-of-magnitude were found between resistor and whole body doses. The outcome of the work was to derive correction / calibration factors that can be applied to estimate whole body doses from OSL/TL readings, the accurate application of which would depend on the knowledge of the exposure geometry and the degree of conservatism acceptable for the dose assessment.