Objective.This work investigates the use of Al2O3:C and Al2O3:C,Mg optically stimulated luminescence (OSL) detectors to determine both the dose and the radiation quality in light ion beams. The radiation quality is here expressed through either the linear energy transfer (LET) or the closely related metricQeff, which depends on the particle's speed and effective charge. The derived LET andQeffvalues are applied to improve the dosimetry in light ion beams.Approach.OSL detectors were irradiated in mono-energetic1H-,4He-,12C-, and16O-ion beams. The OSL signal is associated with two emission bands that were separated using a pulsed stimulation technique and subjected to automatic corrections based on reference irradiations. Each emission band was investigated independently for dosimetry, and the ratio of the two emission intensities was parameterized as a function of fluence- and dose-averaged LET, as well asQeff. The determined radiation quality was subsequently applied to correct the dose for ionization quenching.Main results.For both materials, theQeffdeterminations in1H- and4He-ion beams are within 5 % of the Monte Carlo simulated values. Using the determined radiation quality metrics to correct the nonlinear (ionization quenched) detector response leads to doses within 2 % of the reference doses.Significance.Al2O3:C and Al2O3:C,Mg OSL detectors are applicable for dosimetry and radiation quality estimations in1H- and4He-ions. Only Al2O3:C,Mg shows promising results for dosimetry in12C-ions. Across both materials and the investigated ions, the estimatedQeffvalues were less sensitive to the ion types than the estimated LET values were. The reduced uncertainties suggest new possibilities for simultaneously estimating the physical and biological dose in particle therapy with OSL detectors.
The impact of Quaternary climate change on landscape evolution, and more specifically the timing of incision of the overdeepened Alpine valleys, remains difficult to quantify with existing thermochronometric methods. Thermochronometers are used to determine rates of rock cooling, however most techniques are insensitive to temperature changes <60 °C that occur within the last kms of Earth’s crust. Recording cooling rates within this temperature range is essential if the impact of glacial-interglacial cycles on rock exhumation is to be resolved.Electron spin resonance (ESR) thermochronometry applied to quartz minerals has the potential to span this thermal (and temporal) gap. We are developing this method by building upon previous studies (e.g. Scherrer, 1993) with the ultimate aim of constraining the timing of incision of the Rhône valley. Preliminary data from the Japanese Alps (King et al., 2020) indicate that ESR thermochronometry could resolve rates of <1 mm/yr over Quaternary timescales.To determine a rock cooling history using ESR thermochronometry, signal accumulation and signal thermal loss must be robustly determined within the laboratory. We have collected a series of geological samples including rocks from boreholes that have known isothermal histories to investigate the potential of this technique. Our objective is to use the latter rocks to confirm the validity of our laboratory measurements and data-fitting/numerical models. Specifically, we have investigated known-thermal history samples from the MIZ1 borehole (Japan) and the KTB borehole (Germany) as well as samples from Sion in the Western European Alps.Preliminary data reveal that the ESR dose response and thermal decay of different quartz samples is highly variable. Whereas the Al-centre of some samples exhibits linear dose response to laboratory irradiation up to 15 kGy, the Al-centre of other samples exhibits exponential, or double-exponential growth and saturates at doses of 3-4 kGy. The Ti-centre of most samples is well described by a single saturating exponential function, however samples from the MIZ1 borehole exhibit pronounced sub-linearity in the low-dose response region. Furthermore, whereas for some samples the Al-centre is less thermally stable than the Ti-centre, for other samples the inverse is observed. These observations suggest that a uniform measurement protocol and data-fitting approach may not be appropriate for quartz ESR data.Inversion of two KTB samples yielded temperatures within uncertainty of borehole temperature, however results for the MIZ1 borehole are more variable and can only recover temperature at best within ~10%. Investigations into the cause of the poor results for the MIZ1 borehole are ongoing (i.e. measurement protocol, data-fitting/numerical model) and will be discussed. Preliminary data from Sion are promising and reveal consistent cooling rates. Scherer, T., Agel, A., and Hafner S. S.: Determination of uplift rates using ESR investigations of quartz, KTB Rep. 93-2. Kontinentales Tiefbohrprogram der Bundesrepublic Deutschland Niedersächs. Landesamt Bodenforsch., Hannover, 121–124, 1993.King, G.E., Tsukamoto, S., Herman, F., Biswas, R.H., Sueoka, S., Tagami, T. Electron spin resonance (ESR) thermochronometry of the Hida range of the Japanese Alps: validation and future potential. Geochronology 2, no. 1 (2020): 1-15.   
Abstract Objective. The aim of this work is to investigate the dose rate dependence of thermoluminescence and optically stimulated luminescence detectors (TLDs and OSLDs) in a wide uniform ultra-high dose rate electron beam and demonstrate the potential use of TLDs and OSLDs to correct the ion recombination in air-filled ionization chambers. This study avoids previously reported complications related to the field size and homogeneity. Approach. Two types of OSLDs (BeO and Al 2 O 3 :C) and three types of TLDs (LiF:Mg,Ti, LiF:Mg,Cu,P, CaF 2 :Tm) were irradiated simultaneously in a uniform 16 MeV electron beam generated by a clinically decommissioned C-Arm LINAC, modified to deliver doses per pulse between 8.3 × 10 −4 Gy and 1.255 Gy, corresponding to instantaneous dose rates between 2 × 10 2 Gy s −1 and 3 × 10 5 Gy s −1 . A prototype ultra-thin parallel plate ionization chamber was employed as reference detector. Main results. Reproducible results were achieved both at conventional (standard deviation of the data <2%) and at the highest dose per pulse (standard deviation of the data <4%). No trend in the dose rate response of the TLDs and OSLDs was observed in the investigated dose per pulse range. The Al 2 O 3 :C OSLD was found to be the most precise detector, with a standard deviation of the data <2% at all investigated dose rates and dose levels. Significance. The dose rate independence of the investigated TLDs and OSLDs make them good candidates for dosimetry at ultra-high dose rates, at least up to 3 × 10 5 Gy s −1 . A dose rate independent method to measure the dose per pulse is proposed, which can be applied to characterize ultra-high dose rate electron beams and correct for ion recombination in ionization chambers.
The objective of this work is to apply a model that accounts for the presence of shallow traps to the analysis of pulsed optically stimulated luminescence (POSL) data, which is used to characterize the luminescence lifetime and thermal quenching of luminescent materials. In particular, we focus on the analysis of photon arrival time distribution (PATD) data obtained by POSL readouts of irradiated materials. To achieve this, we present the detailed analysis of a PATD experiment over a range of readout temperatures of a well-known dosimetric material, Al2O3:C. Hitherto, an exact model accounting for the previously observed luminescence lifetime over-estimation is missing. Herein, we apply a proposed model that accounts for the influence of shallow traps and show how this model corrects for the luminescence lifetime over-estimation and introduces the temperature-dependent shallow trap lifetime as a new parameter. We furthermore show that populated deep electron traps lead to a stronger shallow trap occupation, which could be quantified with our model. The results are relevant for both the interpretation of thermal quenching models of Al2O3:C and, more generally, for lifetime measurements in luminescent materials.
The objective of this work is to assess the photon energy and angle response of the radiophotoluminescence (RPL) personal dosimetry system used at the Paul Scherrer Institute (PSI) in terms of the operational quantities for external radiation exposure personal dose, Hp, and personal absorbed dose in local skin, Dlocal skin, defined in the Report 95 of the International Commission on Radiation Measurements and Units (ICRU). The RPL responses in terms of the "new" ICRU Report 95 quantities to a range of photon energies and irradiation angles were calculated using the RPL responses in terms of the personal dose equivalent Hp(10) and Hp(0.07) from the ICRU Report 51, previously obtained during commissioning of the RPL system, and the conversion coefficients from air kerma to the various operational quantities. The indicated value provided by the current dosimetry algorithm over-estimates the personal dose, Hp, in the low-energy range (¡ 33 keV), whereas the estimation for the personal absorbed dose in local skin, Dlocal skin, with the current system is satisfactory. A new dosimetry algorithm was developed making use of the five signals obtained from the RPL detectors, corresponding to the signal from regions of RPL glass under five different filters, to improve the Hp estimation by the RPL dosimeters. The results indicate that, in this case, the new algorithm may be sufficient to achieve satisfactory photon energy and angle response in terms of the ICRU Report 95 quantity Hp without a physical redesign of the dosimeter badges. A few photon mixed fields were also investigated, but a complete algorithm for photon-beta mixed field remains to be developed.
The effective management of radiological emergencies where members of the public not carrying conventional dosimeter have been exposed to doses of ionising radiation requires individual dose estimates to support medical triage. Biological and physical methods have been developed to address this issue. New materials and techniques have been sought to reinforce preparedness for such emergencies. Alternative materials, such as clothing, shoes, paper, plastic items, nail polish or banknotes were investigated using thermoluminescence (TL) and optically stimulated luminescence (OSL).
Most of the materials and fabric tested exhibited either no detectable response to dose using luminescence technique, or a weak response yielding detection limits above 2 Gy, with the exceptions of a blue polyester fabric responding to infra-red stimulated luminescence (IRSL) and some types of polymer-based fabric that were found to have luminescence favourable characteristics for short - term dosimetry and particularly those containing mineral fillers.
The most promising were fabrics containing calcium carbonate fillers, where the TL response to β radiations was measured with a detection limit as low as 4 mGy, and a relatively low native signal in the region of interest (≤ 200 °C). The fading was found to be slower for samples stored at -15 °C compared with samples stored at ambient temperature. A blind test was carried out and confirmed the potential of bags containing calcium carbonate fillers to provide reliable dose estimate for radiological triage. Furthermore, the TL signal of calcium carbonate fillers contained in the fabric of bags offers several advantages for accident dosimetry compared with other methods, such as a rapid dose assessment, the low cost value of the material and availability, and the possibility to map radiological doses is the fabric covers sufficient surface.
The objective of this work is to review and assess the potential of MgB4O7:Ce,Li to fill in the gaps where the need for a new material for optically stimulated luminescence (OSL) dosimetry has been identified. We offer a critical assessment of the operational properties of MgB4O7:Ce,Li for OSL dosimetry, as reviewed in the literature and complemented by measurements of thermoluminescence spectroscopy, sensitivity, thermal stability, lifetime of the luminescence emission, dose response at high doses (>1000 Gy), fading and bleachability. Overall, compared with Al2O3:C, for example, MgB4O7:Ce,Li shows a comparable OSL signal intensity following exposure to ionizing radiation, a higher saturation limit (ca 7000 Gy) and a shorter luminescence lifetime (31.5 ns). MgB4O7:Ce,Li is, however, not yet an optimum material for OSL dosimetry, as it exhibits anomalous fading and shallow traps. Further optimization is therefore needed, and possible avenues of investigation encompass gaining a better understanding of the roles of the synthesis route and dopants and of the nature of defects.
X-band Electron Paramagnetic Resonance (EPR) of quartz requires the irradiation of samples with volumes of ca 3 mm3 , which can be conveniently achieved using commercially available instruments such as the 50 keV X-ray Dose manufactured by Freiberg Instruments. However, X-rays at such low energies can result in highly heterogeneous absorbed doses. In this contribution we use Monte-Carlo particle transport simulations (MCNP6) to characterise the heterogeneity of the radiation field in a 3 mm inner-diameter EPR sample tube irradiated using a 50 kV X-ray generator. From these simulations, we demonstrate that the use of an aluminium filter (200 µm) is redundant when irradiating samples in glass tubes (500 µm wall thickness). Simulations of grain-by-grain absorbed doses across the tubes indicate a maximum of 20 % axial heterogeneity for grains at the tube centre, even when the sample is rotated throughout irradiation. Single-grain luminescence dosimetry measurements were used to experimentally validate the heterogeneity predicted, confirming the modelling results. EPR dosimetry calibration of the X-ray source yielded a dose rate of 0.206 ± 0.005 Gy·s-1 .
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