ALBERT

Description: 〈p〉Publication date: Available online 5 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Hui-Yu Tsai, Hsin-Yu Chen, Ming-Wei Lee, Ze Wang, Sheng-Pin Tseng, Ji-Hong Hong, Meei-Ling Jan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Prompt-gamma Compton imaging (PGCI) has been presented as a promising 〈em〉in-vivo〈/em〉 method for proton range verification. An accurate estimation of the Bragg-peak position can potentially be achieved by imaging high-energy prompt-gamma rays (in the range of several MeV). Therefore, scintillation detectors with thick and high Z crystals are mostly used as Compton absorbers for high-energy gamma-ray detection. However, an absorber using thick crystals degrades the angular resolution unless the absorber can provide continuous depth-of-interaction (DOI) measurement. The study investigated various detector configurations using thick crystals for developing a Compton absorber with DOI resolving capability without compromising energy performance. Two groups of lutetium yttrium oxyorthosilicate (LYSO) with dimensions of 1.8 × 1.8 × 50 mm〈sup〉3〈/sup〉 and 1.8 × 1.8 × 20 mm〈sup〉3〈/sup〉 LYSO arrays, and each with four different surface treatments (combining crystal surface finishing and type of reflector coverage), were constructed for the study. The DOI detector utilized the dual-ended readout of pixelated scintillator arrays for depth encoding. The results revealed that the influences of type of the reflector coverage and crystal surface roughness on the performance of the DOI detectors for the 50- and 20-mm-thick LYSO differed greatly. Moreover, the combined use of the proposed partial inter-crystal reflector coverage and the unpolished surface finishing on the 50-mm-thick crystals were shown to improve the DOI resolution without compromising the energy performance but degraded the flood map quality. These results provide useful guidance for selecting an applicable Compton DOI absorber design for developing a high-performance PGCI system.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): I.S. Peracchi, J. Vohradsky, S. Guatelli, D. Bolst, L.T. Tran, D.A. Prokopovich, A.B. Rosenfeld〈/p〉 〈div xml:lang="en"〉 〈h5〉〈span〉Abstract〈/span〉〈/h5〉 〈div〉 〈p〉Astronauts are exposed to high-energy cosmic radiation which may have harmful health effects. At the altitude of the International Space Station (ISS), the main radiation sources are Galactic Cosmic Rays (GCRs), Solar Particle Events (SPEs) and trapped protons of the Van Allen Belts. The radiation field mainly consists of protons, helium nuclei and heavy ions with energies up to hundreds of GeV/n. A powerful approach to determine the effect of space radiation on astronauts is microdosimetry. The Centre for Medical Radiation Physics is active in the development of Silicon-On-Insulator (SOI) microdosimeters, as an alternative to Tissue Equivalent Proportional Counters (TEPCs) for radiation protection purposes. SOI microdosimeters are portable and do not require a high-voltage power supply. They consist of a matrix of silicon Sensitive Volumes (SV), which mimic the dimensions of biological cells.〈/p〉 〈p〉In this study, we investigated for the first time the response of the 3D “Mushroom” microdosimeter, a type of SOI microdosimeter in the Columbus module of the ISS. Tissue-equivalent microdosimetric spectra of GCRs, SPEs, and trapped protons were obtained to estimate the dose equivalent delivered to the astronauts. Results demonstrate a non-negligible production of secondary particles due to the propagation of space radiation through the wall of the Columbus and the microdosimeter. A number of heavy ions were detected with high lineal energies, these events pose a significant hazard in terms of radiation protection.〈/p〉 〈p〉Moreover, the dose evaluation shows a good agreement with experimental data found in the literature, confirming the suitability of our Geant4 model and the feasibility of using the SOI microdosimeter for ISS astronauts’ personal dosimetry.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 9 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): David Strebler, Svenja Riedesel, Georgina King, Dominik Brill, Helmut Brückner〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉During the last decades, luminescence dating has entered a phase of diversification. This evolution is strongly linked to a series of technical advances, including but not limited to the improvement of EMCCD cameras and the use of violet and yellow LEDs. New measurement techniques have been developed, such as post infra-red infra-red stimulated luminescence (postIR-IRSL) measurement protocols and thermally-transferred OSL (TT-OSL), and the luminescence properties of new materials, such as gypsum and apatite, have been reinvestigated.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 128〈/p〉 〈p〉Author(s): F. Berlier, F. Cardellini, E. Chiaberto, L. Garlati, D. Giuffrida, M. Faure Ragani, F. Leonardi, M. Magnoni, G. Minchillo, A. Prandstatter, E. Serena, R. Trevisi, R. Tripodi, S. Verdelocco, M. Veschetti〈/p〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 127〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 128〈/p〉 〈p〉Author(s): A. Nourreddine, R. Barillon, L. Font〈/p〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Alessio Parisi, Luana de Freitas Nascimento, Olivier Van Hoey, Patrice Mégret, Hisashi Kitamura, Satoshi Kodaira, Filip Vanhavere〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Lithium fluoride thermoluminescent radiation detectors with different dopant concentrations (〈sup〉7〈/sup〉LiF:Mg,Ti and 〈sup〉7〈/sup〉LiF:Mg,Cu,P) were exposed to 〈sup〉1〈/sup〉H and 〈sup〉4〈/sup〉He ions at the Heavy Ion Medical Accelerator in Chiba (HIMAC) in order to investigate their response to energetic light charged particles. Computer simulations with the Monte Carlo code PHITS were performed for a better interpretation of the experimental data. The results were compared with literature efficiency data and with the results of a recently developed microdosimetric efficiency model. In case of the main peak signal of 〈sup〉7〈/sup〉LiF:Mg,Ti detectors, the determined efficiency values are in good agreement with previous investigations. Discrepancies in the efficiency of high temperature signal due to well-known non-linearity effects are reported. For 〈sup〉7〈/sup〉LiF:Mg,Cu,P detectors, an anomalous thermoluminescence behavior in the low temperature part of the signal was found and discussed. Depending on the light quantification process, differences up to 30% in the dose assessment can be obtained, affecting also the relative efficiency determination process. An explanation of this phenomenon as a consequence of local migration of the charged carriers between the low temperature peaks and the main peak is presented. The implications of these findings on the use of LiF:Mg,Cu,P detectors in radiation environments characterized by the presence of 〈sup〉1〈/sup〉H and 〈sup〉4〈/sup〉He ions (i.e. space and proton therapy) are discussed. In order to avoid the occurrence of this anomalous behavior, it is advised to pre-heat the detectors after energetic light particle exposures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Chen Wang, Shi-Lun Guo, Zhi-Yuan Chang, Guo-Rong Liu, Yong-Gang Zhao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Two parameter approach –a new technique has been devised and tested to identify and distinguish Pu–bearing particles from U-bearing particles. This technique can be used to select rare and microscopic Pu-bearing particles from environmental samples, such as in soil, water, air (aerosol) and swipe samples from the wall of buildings and surfaces of machines in nuclear factories. Some amount of Pu and U standard reference materials were respectively added to cellulose nitrate (CN) solution and dropped some quantity of the solution on mica plates and dried to from CN sheets. CR-39 track detectors were used to record tracks of α particles emitted from the Pu or U particles in CN sheets. After etching of CR-39 plates, α track stars were developed and can be seen under optical microscope. Tracks shapes of α particles in the stars were investigated. We found that at certain interval of etching time, the tip part of α tracks of Pu was very sharp, but the tip part of α tracks of U was blunted with spherical tips. The ratio Rt/Ro of the diameter (Rt) of tip point to the diameter (Ro) of the round track in center area of star is a superior parameter to identify Pu from U particles. The Rt/Ro measurements should be carried at a certain distance from the center point. The two parameter approach has been using in nuclear safeguards and nuclear forensics to analyze isotopic compositions and age of Pu samples.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Larisa Grigorjeva, Aleksejs Zolotarjovs, Donats Millers, Krisjanis Smits, Peter Krug, Johannes Stollenwerk, Alan Osman, Thomas Tenostendarp〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉For many years doped α-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 has attracted interest as a dosimeter for personal, environment monitoring and food control. The alumina single crystal growth is a difficult process; however, materials in form of powders, ceramics and coating are possible to obtain. In this study for the first time Cr doped α-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 powders were prepared by DC reactive magnetron sputtering followed by milling and oxidation. The morphology and phase analysis was performed; content of residual impurities was determined and thermostimulated glow curves were measured after different x-ray irradiation times (radiation doses). The prepared powder shows the dosimetry properties up to 20 kGy dose.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Hiroshi Yasuda, Kazuaki Yajima〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉International Commission on Radiological Protection recommends that aircraft crew and frequent flyers be informed of their individual doses received from cosmic radiation onboard aircrafts. The cosmic radiation dose in aviation is generally assessed by model calculations. In Japan, the code “JISCARD EX” is used since 2007 for management of cosmic radiation exposure of aircraft crew. In the present study, the precision of this code was investigated in regard to neutrons which contribute the most to the effective dose in aviation. Measurements of cosmic neutrons were performed with two moderator-type neutron monitors having different response functions: a conventional-type rem meter (NCN1) and an extended energy-range rem meter (WENDI-II) in four long-haul flights to Singapore, Sydney, Washington, D.C. and London from Japan (Narita or Kansai airport). Through the combined analyses of these measurements, the contribution of high-energy (〉15 MeV) neutron component was estimated. The ambient dose equivalents, H*(10), measured with WENDI-II agreed well with the calculations made by JISCARD EX, while the contribution of the high-energy component obtained as the difference between the measured H*(10) values of two monitors was systematically higher than the model calculations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 27 April 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): H.M. Roberts, G.A.T. Duller, M. Gunn, C.R. Cousins, R.E. Cross, D. Langstaff〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In recent years a number of portable instruments have been built for measuring the optically stimulated luminescence (OSL) signal from naturally occurring minerals. Some of these instruments have incorporated ionising radiation sources, giving the possibility of determining an equivalent dose (D〈sub〉e〈/sub〉), but little use has been made of these. One challenge has been that heating samples in this type of equipment is a major engineering challenge, yet methods for D〈sub〉e〈/sub〉 determination use thermal pretreatments to remove charge from unstable traps, making signals arising from irradiation in nature and the laboratory comparable. This paper explores three strategies for obtaining accurate estimates of the D〈sub〉e〈/sub〉 of samples in situations where thermal treatments are not possible: (1) deriving a correction factor based on comparing D〈sub〉e〈/sub〉 values obtained using protocols with and without heating; (2) removing the contribution from the 110 °C TL peak and other unstable defects by component fitting the unheated OSL signal; and (3) adding a small beta dose to the sample prior to measurement of the natural luminescence signal so that the 110 °C TL peak is filled, making this measurement comparable with regeneration measurements where this peak is also populated. All three methods are promising when applied to quartz that has been physically separated from samples using standard laboratory procedures. The next step in this work will be to explore whether such methods can be applied to mixed mineral assemblages as would be encountered in the field.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 7 July 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Minqiang Bu, Andrew Sean Murray, Myungho Kook, Louise Maria Helsted, Jan-Pieter Buylaert, Kristina Jørkov Thomsen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A recent inter-comparison (Murray et al., 2015) has helped to highlight variability in the measurement of dose rate between luminescence laboratories. Part of this variability probably reflects the difficulties of homogenising and dissolving samples so that the 〈500 mg used in e.g. ICP-MS and NAA is representative. High resolution gamma spectrometry is the obvious alternative because it can measure samples 100–1000 times larger, but the instrumentation is low-throughput, high capital and running cost, and requires skilled personnel to maintain operation over many years. Here we investigate the potential of traditional low-cost, low maintenance alternatives based on a 3” × 3” NaI(Tl) scintillation crystal. The temperature stability is investigated, and a linear (with intercept) correction for spectra drift based on the 1.46 MeV peak from 〈sup〉40〈/sup〉K and the ∼100 keV composite X-ray peak from uranium and thorium is shown to minimise this problem. Using a calibration based on wax impregnated standards, the minimum detection limits (MDL) are 25 Bq/kg (〈sup〉40〈/sup〉K), 4.8 Bq/kg (〈sup〉238〈/sup〉U), 2.5 Bq/kg (〈sup〉232〈/sup〉Th) for 250–300 g of sample; systematic deviations around the expected values are also shown to be acceptable as the MDL is approached. Finally, we compare the activity concentrations and resulting dry dose rates derived from our NaI-based system with those from routine high resolution gamma spectrometry, and conclude that the new analytical facility is very suitable for accurate and precise dose rate determination.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Lovisa Waldner, Christian Bernhardsson〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉In this paper, NaCl pellets are produced in-house from ordinary household salt using simple and accessible methods, for the purpose of suggesting a cost-effective and available tool for various optically stimulated luminescence dosimetry applications. First, the pellets are investigated in terms of optimal configuration by varying combinations of grain sizes and compression forces. Then, the pellets with the optimal configuration are further investigated in terms of dosimetric properties such as signal-dose response, dose estimation, reproducibility, radiation induced sensitisation, detection limits and signal stability over time. The radiation induced OSL signals are read at room temperature and dose estimations are performed using one calibration dose.〈/p〉 〈p〉The optimal pellet configuration, for the three salts investigated, was achieved with 100–400 μm sized salt grains and a compression force of 3.0 ± 0.5 tons. With the proposed NaCl pellets, readout and calibration procedure, it is possible to achieve a linear dose response in the dose range from 0 to 300 mGy. When using a calibration dose for signal normalisation the reproducibility of the radiation induced OSL signal is within 1.5% and when using the most optimal calibration dose for each salt the estimated dose is within 3% of the given dose. The detection limits for the salts investigated are, in terms of minimum detectable dose, between 5 and 21 μGy. Considering these findings and the overall cost of manufacturing NaCl pellets i.e. the worldwide availability, the proposed method opens for radiation protection measurements that have so far been too expensive or impossible.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 May 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): J. Carter, A.J. Cresswell, T.C. Kinnaird, L.A. Carmichael, S. Murphy, D.C.W. Sanderson〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Previous studies have suggested that excess variations from single-photon counting systems used in luminescence dating may result in underestimation of errors and profoundly influence age models. In this study ten different photon counting systems have been investigated to explore this effect with a greater number of photomultiplier types and instrumental architectures. It is shown that radiation induced phosphorescence from F1 feldspar produces a controllable low-level light source whose local variance approximates Poisson expectations. However excess variation in dark counts was observed to varying extents from all systems. The excess variance is slightly anti-correlated with the age of the system, with older devices conforming more closely to Poisson behaviour. This observation does not seem to fit the hypothesis that enhanced levels of helium diffused into older tubes increase non-Poisson components. It was noted that a significant part of the non-Poisson behaviour was associated with multi-event pulse streams within time series. Work was also undertaken to develop mitigation methods for data analysis and to examine the implications for dating uncertainties in a test case. A Poisson-filtering algorithm was developed to identify and remove improbable multi-event streams. Application to data from signal-limited single grains of sediments from a Neolithic chambered tomb in Corsica has shown that, for this case, removing non-Poisson components improves the robustness of retained data, but has less influence on overall dating precision or accuracy. In signal limited applications use of this algorithm to remove one source of excess variation is beneficial. The algorithm and test data are appended to facilitate this.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 18 August 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): E.F. Rades, R. Sohbati, C. Lüthgens, M. Jain, A.S. Murray〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉In this study, we investigate the potential of rock surfaces to provide luminescence burial ages for boulders from moraine deposits. We sampled four boulders from a terminal moraine at the Malta Valley, Austria, all deposited ∼2 m below the present ground surface, and measured the IRSL signal as a function of depth into the boulder surfaces. It is clear from these profiles that all four boulders were exposed to at least some daylight prior to final deposition, and in one boulder, there is evidence for multiple exposure/burial events. The profiles show that the luminescence signal at the surface of two boulders must have been completely zeroed before burial. The burial doses derived from these two well-reset surfaces can thus be safely used to calculate burial ages, which may be the same as the depositional age of the terminal moraine. The IRSL signals from both boulders seem to suffer from anomalous fading with g-values of up to 15% decade〈sup〉−1〈/sup〉. The younger fading-corrected age of ∼14 ka is in agreement with the deposition of the terminal moraine and coincides with the assumed Gschnitz stadial, while the older age of ∼39 ka most likely represents an earlier event during which this boulder was exposed to light.〈/p〉 〈p〉Our results suggest that there is a high probability of sampling light-exposed and even well-bleached boulders from moraine deposits. We thus conclude that rock surface luminescence dating offers the possibility of obtaining reliable ages for moraine deposition. Even boulders which are partially bleached and thus not suitable for dating can provide insight into transportation pathways as well as depositional processes in glacial environments leading to a better understanding of the dynamics of glaciers.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Eren Şahiner, M. Korhan Erturaç, Georgios S. Polymeris, Niyazi Meriç〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, two different equivalent dose protocols using Infrared stimulated luminescence (IRSL), namely post IR (pIRIR) and Multi-Elevated temperature post IRSL (MET-pIRIR) were applied to geological samples collected from terrace staircases formed along the Sakarya River, western Anatolia, Eastern Marmara Region, Turkey. Methodological aspects were studied, as the IRSL signal, which is measured at elevated temperatures, yields unusual shape, consisting of an initial increasing part which is followed by the well-known decaying shape. Therefore, according to signal shape, instead of de-convolving the IRSL signals, equivalent dose estimations were performed using different time integration intervals of the emission. The results constitute of two groups, yielding equivalent dose values, in the range between 55 and 110 Gy for selected samples. Since de-convolution of the IRSL signals is both time consuming as well as difficult, mostly due to the presence of tunneling localized transitions, the selection of the appropriate/optimum time integration interval was discussed. The outcomes of this study indicate that IR stimulations at higher temperatures ranging from 200 to 250 °C are useful for feldspar dating, providing that initial increasing part will be eliminated. The thermal activation energy of that unusual part of the signal was calculated around 0.035 ± 0.005 eV using Arrhenius plot, indicating that it may arise from phonon lattice interactions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): G. Gambarini, D. Bettega, A. Gebbia, M. Felisi, E. Artuso, D. Giove, V. Klupak, L. Viererbl, M. Vins〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The various dose components generated by epithermal neutron beams in tissue-equivalent materials have different spatial distributions that also depend on the size and volume of the irradiated volume. NCT dosimetry requires the separate determination of dose components having different LET, because of their different RBE. Monte Carlo simulations have been developed concerning the absorbed doses and thermal neutron fluences, to investigate the extent of the differences that may occur by changing the shape and size of the irradiated volumes. Moreover, the doses and fluences that occur if specific isotopes (〈sup〉10〈/sup〉B, 〈sup〉14〈/sup〉N, 〈sup〉157〈/sup〉Gd) are added to water have been evaluated.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): Shingo Kobayashi, Takayuki Shinomiya, Yukio Uchihori, Hisashi Kitamura, Shinya Iwamoto, Kentaro Kojima, Yuichi Goto, Shinobu Kobayashi, Kazuo Tanimoto, Yasuo Terakado, Yasunari Nakajima, Hiroko Yoshida, Akio Yamanishi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An X-ray detector which we call the characteristic X-ray detector (CXRD) with a large sensitive area of 199 cm〈sup〉2〈/sup〉 was studied as a candidate imaging device with high sensitivity, light weight and low-cost features to visualize environmental 〈sup〉137〈/sup〉Cs deposited after the Fukushima Dai-ichi Nuclear Power Station accident. The CXRD has a directionality for its sensitivity and it is able to visualize a spatial distribution of 〈sup〉137〈/sup〉Cs by scanning the flux of 32 keV characteristic X-rays due to disintegration of 〈sup〉137〈/sup〉Cs instead of imaging the 662 keV gamma-rays from 〈sup〉137〈/sup〉Cs. Our experimental results showed that the counting efficiency of the CXRD was 105 counts per second for a 1 MBq 〈sup〉137〈/sup〉Cs source at a distance of 1 m and the CXRD had a very high counting efficiency for a certain direction. We estimated the potential sensitivity of the CXRD when it was used in the scanning mode to image an area of 2π sr. The CXRD was tested in a contaminated forest in Fukushima Prefecture and images of the spatial distribution of 〈sup〉137〈/sup〉Cs in the forest were successfully obtained. We found that most of the 〈sup〉137〈/sup〉Cs was present in the forest floor and no 〈sup〉137〈/sup〉Cs was detected in the atmosphere and the tree canopy. The CXRD is useful because of its low cost, light weight and high sensitivity as a 〈sup〉137〈/sup〉Cs imaging device for monitoring post devices in forests and as a portable imaging device to confirm the effectiveness of decontamination work.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): George S. Polymeris, Eren Şahiner, Engin Aşlar, George Kitis, Niyazi Meriç〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermally assisted optıcally stimulated luminescence (TA – OSL) stands as an experimental technique which encompasses the simultaneous use of optical and thermal stimulation. The technique can effectively stimulate electrons from traps with delocalization temperatures beyond 500 °C, also known as very deep traps (VDTs). For the case of quartz, TA – OSL is usually measured isothermally, at constant elevated temperature, yielding a decaying shape similar to that reported for the cases of conventional OSL. This feature is prevalent for all quartz samples. In the framework of the present study, a deconvolution analysis was attempted on the corresponding isothermal TA – OSL decay curves of 5 different quartz samples collected from the Aegean Anatolia region, Turkey. Deconvolution was performed on isothermal TA – OSL signals measured at a wide range of stimulation temperatures. Combinations of three different, well established, contemporary luminescence models were applied, two involving delocalized recombination via the conduction band, namely general order kinetics and photo-transfer models, along with one involving both tunneling recombination and delocalized recombination pathways. The use of the model of general order kinetics alone gives physically meaningless results, as the photo-ionization cross section of a specific component indicates a behavior which contradicts the luminescence models, yielding inverse Arrhenius law behavior. A combination of the general order kinetics and the photo-transfer models yields results without major physical inconsistencies. However, the thermal quenching parameters obtained according to the deconvolution procedure do not agree with the corresponding prevalent or even representative values for quartz. This latter feature, in conjunction to (a) the shapes of the residual thermoluminescence signal after TA – OSL, (b) the shapes of the TA – OSL with linear heating and (c) the shapes of the isothermal TA – OSL curves normalized over the initial intensity, suggest that the major part of the TA – OSL signal recombines via tunneling. The use of a combination of tunneling plus general order kinetic models has also been applied for the deconvolution analysis. The physically meaningful corresponding results indicate that in the absence of any other specific luminescence model for the isothermal TA – OSL decay curves, the latter combination of these two models provides the optimum case, not only for deconvolving the isothermal TA – OSL in quartz, but also for providing further insight to the physics of the phenomenon.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 30 April 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Madhav Krishna Murari, Sebastian Kreutzer, Markus Fuchs〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We discuss the dose recovery behaviour of IR-RF from K-rich feldspar extracts from modern-analogue sediment samples. The zero-dose of these samples was confirmed from previous quartz OSL and feldspar IRSL measurements. In our experiments, the IR-RF curve (RF〈sub〉nat〈/sub〉) from the naturally bleached sample was taken as a regenerated curve within dose recovery experiment. We report that the obtained dose varies by 15% to 23% from the given dose, when recovered from naturally bleached IR-RF curves. However, it matches with the IR-RF regenerated (RF〈sub〉reg〈/sub〉) curve bleached with a solar simulator. We discuss the potential reasons for the observed differences and present two correction methods: background subtraction and vertical curve sliding. We conclude that a given dose can be successfully recovered up to 3,600 Gy if the vertical sliding method is applied. Our results further indicate that an applied signal correction by vertical sliding improves the overall accuracy of IR-RF dose estimations. The incorrect dose recovery of naturally bleached samples without signal correction implies that the estimated palaeodoses from natural samples may not be reliably reconstructed if no correction is applied.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 14 April 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): A.S. Murray, L.M. Helsted, M. Autzen, M. Jain, J.P. Buylaert〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Murray et al. (2015) described an international inter-comparison of dose rate measurements undertaken using a homogenised beach ridge sand from Jutland, Denmark. The measured concentrations for 〈sup〉226〈/sup〉Ra, 〈sup〉232〈/sup〉Th and 〈sup〉40〈/sup〉K from different laboratories varied considerably, with relative standard deviations of 26% (n = 8), 59% (n = 23) and 15% (n = 23), respectively. In contrast, the relative standard deviations observed internally within our laboratory were 9%, 11% and 7%, respectively (n = 20), and in addition our mean values were consistent with the global 〈sup〉40〈/sup〉K mean, but significantly different from the 〈sup〉232〈/sup〉Th mean. These problems in both accuracy and precision have led us to examine both the long term performance of our analytical facility, and its calibration. Our approach to the preparation of new absolute 〈sup〉238〈/sup〉U, 〈sup〉232〈/sup〉Th and 〈sup〉40〈/sup〉K standards is outlined and tested against international standards. We also report analyses of the Volkegem (De Corte et al., 2007) and Nussi (Preusser and Kasper, 2001) loess samples, for further comparison with other laboratories.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 19 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Jintang Qin, Jie Chen, Yuetian Li, Liping Zhou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The poor dose recovery ratios reported for the infrared (IR) stimulated luminescence and post-IR IR stimulated luminescence (pIRIR) measurements of potassium feldspar (K-feldspar) have been attributed to the initial sensitivity changes. The change in electron trapping probability was inferred as a possible cause of the initial sensitivity change. However, there is still a lack of experimental evidence. In this study, the electron trapping probability changes were traced by recording the radiofluorescence (RF) emitted in the IR band (IR-RF) during the irradiation steps of the “single regenerative point” dose-recovery-like experiments. The IR-RF data shows that both high temperature heating and the preceding received dose during the laboratory measurements lead to a decrease in electron trapping probability for the sample employed in this study. For the pIRIR〈sub〉290〈/sub〉 signal, a 20% sharp decrease in the trapping probability is induced by the high temperature preheat, irrespective of the dose administered. For the pIRIR〈sub〉225〈/sub〉 and pIRIR〈sub〉170〈/sub〉 signals, the trapping probability decreases more gradually during the measurements for small doses and a 20% sharp decrease is only observed after the aliquot was irradiated with a large dose. The decrease of trapping probability does not always lead to initial sensitivity change. We infer that the heating and dosing may induce an increase in recombination probability, which serves as a compensation mechanism to balance out the trapping probability decrease. The amplitude of recombination probability increase may decrease with the increase of dose, and therefore, the occurrence of initial sensitivity change shows dependence on the type of pIRIR signal and the size of given and test doses.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 18 May 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): M. Lamothe, L. Forget Brisson, F. Hardy〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In an attempt to test feldspar dating techniques that would use both IR〈sub〉50〈/sub〉 and pIRIR〈sub〉225〈/sub〉 equivalent doses, we investigated the impact of various thermal treatments on the recovery of a laboratory dose. It is observed that the most reliable protocols for delivering acceptable recovery ratios may be sample dependant. Appropriate thermal treatments, including a potentially efficient pre-test dose thermal wash (PTD TW) could yield dose recovery ratios in a range of ±5% around unity for both IR〈sub〉50〈/sub〉 and pIRIR〈sub〉225〈/sub〉 signals. These experiments are strong indications that rigorous dose recovery tests should be carried out before the measurement of the equivalent dose of feldspar in double SAR protocols.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Owen M. Williams, Nigel A. Spooner, Barnaby W. Smith, Jillian E. Moffatt〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As part of an investigation into the mechanisms underlying optically stimulated luminescence (OSL) in quartz, we have shone a number of South Australian natural quartzes over a six day measurement period. During this time the OSL signal was recorded over ten decades in time and fell six to seven decades in luminescent intensity. In particular, we observe the presence of a number of steps that appear when the luminescence is displayed in log/log form. In exploring the underlying mechanism, we review both the standard energy band gap model for quartz OSL and the alternative defect pair model and find that the latter can be applied to explain the steps in terms of a nearest neighbour extension.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 April 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): P.G. Hunter, N.A. Spooner, B.W. Smith〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study we investigate the creation of high dose markers in the TL of quartz when irradiated with doses up to and exceeding 8 kGy, with a view to using the characteristics as a potential tool for retrospective dosimetry. Supralinear growth of the 210 °C and 350 °C 480 nm TL peaks was confirmed at high doses, as observed by others. Both peaks decrease abruptly at doses over 16 kGy, which we tentatively attribute to depletion of the 480 nm luminescence centres. Test doses applied after measurement of the high-dose TL showed that the 350 °C TL peak retained the sensitisation to dose, whereas the 210 °C TL peak did not. The 350 °C TL peak retains a significant marker of prior radiation exposure even after a 1-h annealing at 400 °C. Kinetic analysis on a quartz sample has shown that at high doses the 210 °C and 350 °C TL peaks have fundamentally the same E and s values as found for low-dose samples. The 12 ka lifetime of the 210 °C peak makes it suitable for retrospective dosimetry.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): Konrad Tudyka, Sebastian Miłosz, Grzegorz Adamiec, Andrzej Bluszcz, Grzegorz Poręba, Łukasz Paszkowski, Aleksander Kolarczyk〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉〈em〉μ〈/em〉Dose is a novel compact analytical instrument for assessing low level 〈sup〉238〈/sup〉U, 〈sup〉235〈/sup〉U, 〈sup〉232〈/sup〉Th decay chains and 〈sup〉40〈/sup〉K radioactivity. The system is equipped with a dual 〈em〉α〈/em〉/〈em〉β〈/em〉 scintillator allowing discrimination between 〈em〉α〈/em〉 and 〈em〉β〈/em〉 particles. The unique built-in pulse analyzer measures the amplitude of each individual pulse, its shape and the time interval between subsequent pulses. This allows the detection of pulse pairs arising from subsequent decays of 〈sup〉214〈/sup〉Bi/〈sup〉214〈/sup〉Po, 〈sup〉220〈/sup〉Rn/〈sup〉216〈/sup〉Po, 〈sup〉212〈/sup〉Bi/〈sup〉212〈/sup〉Po and 〈sup〉219〈/sup〉Rn/〈sup〉215〈/sup〉Po. The obtained 〈em〉α〈/em〉 and 〈em〉β〈/em〉 counts and four separate decay pair counts are used to calculate 〈sup〉238〈/sup〉U, 〈sup〉235〈/sup〉U, 〈sup〉232〈/sup〉Th and 〈sup〉40〈/sup〉K specific activities in measured samples through the use of radioactivity standards. The 〈em〉μ〈/em〉Dose system may be equipped with various photomultipliers and counting containers to assess radionuclide concentrations of samples of masses ranging between 0.4 g and 4 g. As a result, the user can customize the system to their needs and maximize the instrument's performance. The system is controlled by dedicated software with a graphical user interface and modules for system calibration, data visualization, specific radioactivity calculations and dose rate determination using the infinite matrix assumption.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 August 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Lily Bossin, Ian K. Bailiff, Ian Terry〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Alumina substrates, such as those found as surface-mount resistors in mobile phones, are currently the strongest candidate as a surrogate dosimeter material in emergency radiological scenarios using luminescence techniques. However, the rate of fading of the luminescence signal (TL or OSL) imposes a limitation on their longer term use, and also increases the uncertainty in dose assessment. The potential of phototransferred thermoluminescence (PTTL) techniques to access deep traps in alumina substrate samples is reported here. A measurement procedure employing blue (470 nm) illumination was found to produce a PTTL signal with a detection limit of ca 100 mGy, but with a supralinear dose response below 10 Gy. By using a UV source with emission between 307 and 575 nm a linear dose response was obtained within this dose range, although the detection limit was higher (ca 200 mGy), partly arising from the presence of a non-radiation-induced photostimulated TL signal. Pulse annealing experiments indicate that deep traps providing a reservoir of charge are thermally accessible above 500 °C and require annealing to ca 700 °C to thermally clean them. Significantly, using blue illumination, storage experiments performed under dark conditions at room temperature indicate that the loss of charge in the deep traps accessed by the PTTL measurement procedure was less than 30% for storage periods of up to 224 days. Although the physical mechanisms associated with the transfer of charge from the deep traps probed by the PTTL measurements require further clarification, the possibility of significantly reducing the fading observed in conventional TL or OSL measurements introduces a potentially valuable tool in the use of this material for both short and long term dosimetry.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Prasanna Kumar Mondal, Rupa Sarkar, Manas Datta, Barun Kumar Chatterjee〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The 〈sup〉241〈/sup〉Am gamma-ray source has a number of medical and industrial applications. In addition to the gamma-rays the source also could yield neutrons due to the (〈em〉α,xn〈/em〉) reactions with other materials such as oxygen, aluminium etc. While using this source one needs to be aware of the possible unwanted exposure to neutrons and also of wrong results. We have investigated the neutron yield from a 1.85 × 10〈sup〉10〈/sup〉 Bq 〈sup〉241〈/sup〉Am source and found that the source has a neutron yield of 3350 ± 79 neutrons/s. The variation of neutron dose rate and neutron flux with distance from the source is also obtained using superheated droplet detectors. The neutron dose is found to be about two orders of magnitude lower than the gamma-ray dose.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Galina Faershtein, Benny Guralnik, Renske Lambert, Ari Matmon, Naomi Porat〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermally-Transferred Optically Stimulated Luminescence (TT-OSL) from quartz is an extended-range luminescence dating technique, with an assumed potential to date sediments as old as early Pleistocene (0.8–2.6 Ma). However, one of the main drawbacks of the TT-OSL signal is its relatively low thermal stability. The few and scattered estimates in the literature of the relatively low thermal stability highlight the possibility that some reported TT-OSL ages are thermal artefacts (i.e. minimum ages only). In this study, we rigorously investigate the thermal stability of the main TT-OSL source trap, using a combination of laboratory and analytical techniques (varying heating rates, isothermal decay, alongside several models) on multiple aliquots of a modern sand sample from the eastern Mediterranean coastal plain. The varying heating rates method constrains the Arrhenius parameters of the TT-OSL main trap to 〈em〉E〈/em〉 = 1.50 ± 0.06 eV and 〈em〉s〈/em〉 = 10〈sup〉12.8±0.6〈/sup〉 s〈sup〉−1〈/sup〉; these values translate into a trap lifetime of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mn〉3〈/mn〉〈mo〉.〈/mo〉〈msubsup〉〈mn〉2〈/mn〉〈mrow〉〈mo〉−〈/mo〉〈mn〉1.9〈/mn〉〈/mrow〉〈mrow〉〈mo〉+〈/mo〉〈mn〉4.8〈/mn〉〈/mrow〉〈/msubsup〉〈/math〉 Ma at 10 °C. Isothermal decay data further exhibits significant departures from first-order kinetic behavior, which can be well captured by either the general order kinetics model, or a Gaussian distribution of first-order systems. However, extrapolations of these models to geological timescales are at odds with a large volume of observations, thus suggesting that the deviation from first-order kinetics may be a laboratory artefact. Overall, our study reinforces the concern, that thermal loss progressively affects the TT-OSL signal in the Ma-scale age range, and that some previously reported results may be “minimum ages” only.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Seiichi Yamamoto, Hideo Nitta〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We previously developed a radiation detector using a ceramic scintillator made for X-ray computed tomography (CT), Gd〈sub〉3〈/sub〉(GaAl)〈sub〉5〈/sub〉O〈sub〉12〈/sub〉:Ce (GGAG), combined with a position-sensitive photomultiplier tube (PSPMT) for the imaging of radiation. However, GGAG's scintillation wavelength is more suitable for silicon-based photodetectors than PSPMT, and so better performance is expected by combining it with a silicon-based photodetector. Therefore, here we combined a GGAG plate with silicon photomultiplier (Si-PM) arrays to develop a radiation-imaging detector. Our proposed Si-PM-based GGAG radiation-imaging detector consists of a 0.5-mm-thick GGAG plate, a light guide, and an 8 x 8 Si-PM array. The spatial resolutions of this imaging detector surpassed 0.31-mm FWHM for 5.5-MeV alpha particles. The spatial resolution of the Sr-Y-90 beta particles (maximum energy: 2.28 MeV) was ∼0.8 mm FWHM and 0.6-mm FWHM for Ca-45 (maximum energy: 0.24 MeV). The spatial resolutions for Co-57 (122 keV), Am-241 gamma photons (60 keV), and Cs-137 X-rays (∼35 keV) were 0.6-, 0.8-, and 1.0-mm FWHM, respectively. Since GGAG's scintillation decay curves for alpha particles are different from gamma photons or beta particles, we can use pulse-shape discrimination to separate the Am-241 alpha particles from the Cs-137 gamma photons as well as from the Sr-Y-90 beta particles.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Yan Li, Sumiko Tsukamoto, Hao Long, Jingran Zhang, Linhai Yang, Zhong He, Manfred Frechen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The reliability of the fading correction methods for feldspar infrared stimulated luminescence (IRSL) dating in the non-linear part of the dose response curve proposed by Wallinga et al. (2007) (modified after Lamothe et al., 2003) and Kars et al. (2008) was evaluated using samples from the Chinese loess-palaeosol sequence in Luochuan with the reference ages. Two protocols, the post-infrared (IR) IRSL at 225 °C (pIRIR〈sub〉225〈/sub〉) and the pulsed IR at 50 °C, were applied in this study. The natural dose response curve (DRC) for the IR〈sub〉50〈/sub〉 (pre-pIRIR〈sub〉225〈/sub〉), pIRIR〈sub〉225〈/sub〉 and pulsed IR〈sub〉50〈/sub〉 was first constructed. The simulated-natural DRC and the fading corrected ages were then determined. The characteristic saturation dose (〈em〉D〈/em〉〈sub〉0〈/sub〉) of the simulated-natural DRC was found to be larger than that of the natural DRC for the IR〈sub〉50〈/sub〉 (pre-pIRIR〈sub〉225〈/sub〉) and pIRIR〈sub〉225〈/sub〉 signals, whilst the two 〈em〉D〈/em〉〈sub〉0〈/sub〉 values agreed with each other for the pulsed IR〈sub〉50〈/sub〉. The saturation ratio (〈em〉n/N〈/em〉) of the simulated-natural DRC agreed with the natural one within 10% uncertainty for all three signals. The fading corrected ages using these two methods agreed with the reference ages, confirming the reliability of the two fading correction methods. However, our numerical simulation on the fading correction showed that the method of Wallinga et al. (2007) significantly overcorrect ages when the fading rates are larger than 〈em〉ca.〈/em〉 4–5%/decade.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): Michael A. Hupman, Ian G. Hill, Alasdair Syme〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Organic thin film transistors (OTFT) were investigated as a novel radiation detector. The OTFTs were fabricated on a flexible PET substrate with a PMMA dielectric layer and a pentacene semiconductor. OTFTs were irradiated up to 400 Gy using kilovoltage (100 and 180 kVp) and megavoltage (6 and 18 MV) photon beams. One OTFT was irradiated to 1000 Gy using 6 MV to observe the longevity of the device. Irradiating the devices caused a positive threshold voltage shift in each device. The magnitude of the threshold voltage shift per unit dose decreased with accumulated dose until it stabilized after approximately 200 Gy. The sensitivity ranged from 2 to 10 mV/Gy at low accumulated dose and decreased to 0.5–1.5 mV/Gy after 200 Gy of accumulated dose across the various OTFTs. After 400 Gy all of the devices were still functional with a loss in mobility of about 15, 14, 12 and 9% for beam qualities of 100 kV, 180 kV, 6 MV, and 18 MV, respectively. After 1000 Gy using 6 MV the OTFT was still functional with a sensitivity of 0.8 ± 0.1 mV/Gy after 300 Gy. This study showed that an OTFT on a flexible substrate shows a measureable response to photon irradiation of various qualities.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): E.C. Karsu Asal, G.S. Polymeris, G. Kitis〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Themoluminescence (TL) response of CaF〈sub〉2〈/sub〉:Dy (TLD-200) as a function of irradiation temperature was studied in the present work. The irradiation of a TL material at elevated temperatures has a twofold scope: (a) To provide knowledge and insight regarding the possibilities of radiation dosimetry at high temperature environments; (b) The fact that during irradiation at elevated temperatures trap filling and trap emptying take place simultaneously, makes this pre-conditioning the most promising for the reflection in the net glow-curve of competition effects between traps and centres. The irradiation temperature (T〈sub〉irr〈/sub〉) region was between room temperature (RT) and 270 °C in steps of 10 °C. Using the same conditions as far as dose and temperature are concerned, post irradiation annealing (PIA) measurements were also performed, which give only the results of trap emptying. Both experiments were performed using (a) one sample for all measurements (single-aliquot procedure) and (b) two samples for each temperature (multi-aliquot procedure). Deconvolution was also applied in all cases towards investigating the impact of the two protocols on the kinetic parameters of all peaks for this specific material. The results showed that there is not any dependence of the TL response in the case of multi-aliquot procedure. However, in the case of single-aliquot procedure, a very interesting dependence of the TL response on T〈sub〉irr〈/sub〉 is observed only for the last TL peak of TLD-200. These results, although weaker, were also observed in the case of PIA procedure. Activation energies of the high-temperature, more stable peaks yield a dependence on both irradiation and PIA temperatures. The results are discussed in the framework of the trap competition models.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Georgina E. King, Christoph Burow, Helen M. Roberts, Nicholas J.G. Pearce〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The recent introduction of post-IR IRSL measurement protocols has prompted a resurgence in luminescence applications using feldspar, some of which are affected by anomalous fading related signal loss. Many fading-corrected feldspar ages are reported in the literature, however few of those ages have been corrected using the model of Huntley (2006) 〈em〉[Huntley, D.J., 2006. An explanation of the power-law decay of luminescence. Journal of Physics: Condensed Matter 18(4), 1359–1365]〈/em〉. Here we present a new 〈strong〉R〈/strong〉 function that calculates fading-corrected ages using the model of Huntley (2006), implemented with either a single-saturating exponential (1EXP) or general-order kinetic (GOK) fit. We evaluate the performance of the model through (i) contrasting measured and modelled field saturation values for a suite of 41 published saturated samples, and (ii) through using the model to fading-correct feldspar ages of samples with independent age control. Our results indicate that when implemented with 1EXP this model has an accuracy of 10% for predicting sample saturation, but that independent ages may be overestimated when the model is used to fading-correct samples across a range of timescales. In contrast, providing that the dose response curve has been characterised beyond 600 Gy, implementing the Huntley (2006) model with a GOK fit yields accurate age estimations. Modelled age overestimation for 1EXP is associated with dose response curve deviation from a single-saturating exponential. Finally we contrast the laboratory measured light levels of a suite of 50 saturated samples with their corresponding fading rates. We show that these saturated samples may yield 〈em〉D〈/em〉〈sub〉〈em〉e〈/em〉〈/sub〉 values below 〈em〉2D〈/em〉〈sub〉〈em〉0〈/em〉〈/sub〉, and thus that 〈em〉2D〈/em〉〈sub〉〈em〉0〈/em〉〈/sub〉 is not an effective screening criterion for sample saturation where no anomalous fading correction is made.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Shinji Tokonami, Masahiro Hosoda〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present paper summarizes the scientific activities of the authors which have been focused on environmental monitoring and estimating thyroid dose for evacuees of the Fukushima Nuclear Power Plant accident. The radionuclide components of the absorbed dose rates in air obtained by a gamma-ray spectrometer depend on the radioactive plume behavior. Furthermore, continuous measurements by a car-borne survey are important to know the radioactive plume behavior. A few thyroid dose estimations have been obtained by different techniques. Direct measurements by the authors were in agreement with these published estimations. However, the dose from 〈sup〉132〈/sup〉I was not taken into account in the previously published thyroid dose estimation due to the lack of information. After a nuclear accident, prompt thyroid measurements are required, and a standard technique for the measurement of activity in thyroid should be established.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 17 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Sumiko Tsukamoto, Hao Long, Marcus Richter, Yan Li, Georgina E. King, Zhong He, Linhai Yang, Jingran Zhang, Renske Lambert〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The natural electron spin resonance (ESR) dose response curve (DRC) of the Al and Ti centres was constructed for the first time using sand-sized quartz samples from Luochuan, Chinese Loess Plateau. The natural DRC of both centres showed an unexpected early saturation, with characteristic saturation dose (〈em〉D〈/em〉〈sub〉0〈/sub〉) values of ∼760 Gy for the Al centre and ∼650 Gy for the Ti centre, when fitted with a single saturating exponential function. This corresponds to an upper age limit of ∼500 ka (Al centre) and ∼400 ka (Ti centre), using the mean dose rate of 3 Gy/ka. The laboratory DRC of both centres showed much higher saturation dose, but both intensity and 〈em〉D〈/em〉〈sub〉0〈/sub〉 value of the regenerated ESR signals decreased significantly with increasing preheat temperatures. The natural DRC had a better match with the laboratory DRC following higher temperature preheats, ∼210–240 °C for 4 min, suggesting the need for preheating after laboratory irradiation for quartz ESR dating. The results of isothermal heating tests revealed that the thermal lifetime at 10 °C at the studied site was ∼1.5 × 10〈sup〉9〈/sup〉 and ∼1.7 × 10〈sup〉6〈/sup〉 years for the Al and Ti centres. Although the thermal lifetime of these impurity centres could be sample dependent, the relatively short lifetime of the Ti centre contributed to the early saturation of the natural DRC of the Chinese loess. This highlights the importance of investigating the thermal lifetime of signals for dating older samples using ESR.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 1 August 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Ming Luo, Jie Chen, Jinfeng Liu, Jintang Qin, Lewis A. Owen, Fei Han, Huili Yang, Haoran Wang, Boxuan Zhang, Jinhui Yin, Yuehua Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Four gneiss boulders on Holocene glaciofluvial fans offset by the Kongur normal fault in the Chinese Pamir Plateau were sampled to test the reliability and applicability of rock surface luminescence dating. The 〈sup〉10〈/sup〉Be ages of the boulders ranged from 2.1 to 7.5 ka. Depth profiles of luminescence intensity were measured using a modified multi-elevated-temperature post-infrared infrared stimulated luminescence (MET-pIRIR) protocol, in which two consecutive stimulations with different power, 15 and 131 mW/cm〈sup〉2〈/sup〉, were performed for each temperature. The decay rate of the trapped charge at the surface 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mover accent="true"〉〈mrow〉〈mi〉σ〈/mi〉〈msub〉〈mi〉φ〈/mi〉〈mn〉0〈/mn〉〈/msub〉〈/mrow〉〈mo stretchy="true"〉¯〈/mo〉〈/mover〉〈/mrow〉〈/math〉 were calibrated using the 〈sup〉10〈/sup〉Be age for each boulder sample. The resulting values for the parameter 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mover accent="true"〉〈mrow〉〈mi〉σ〈/mi〉〈msub〉〈mi〉φ〈/mi〉〈mn〉0〈/mn〉〈/msub〉〈/mrow〉〈mo stretchy="true"〉¯〈/mo〉〈/mover〉〈/mrow〉〈/math〉 were utilized to estimate the exposure time of other samples. The shielding effect of rock varnish was examined in relation to the attenuation coefficient μ and the wavelength of the sunlight that penetrates a rock surface. Uncertainties in μ derived from fitting each MET-pIRIR signal depth profile, corresponding the parameter 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.gif" overflow="scroll"〉〈mrow〉〈mover accent="true"〉〈mrow〉〈mi〉σ〈/mi〉〈msub〉〈mi〉φ〈/mi〉〈mn〉0〈/mn〉〈/msub〉〈mi〉t〈/mi〉〈/mrow〉〈mo stretchy="true"〉¯〈/mo〉〈/mover〉〈/mrow〉〈/math〉, and calculated ages were too large to allow precise comparisons to be made between vanished and unvarnished rock surfaces. The μ was assumed to be the same for all MET-pIRIR signals, and so was fitted simultaneously to all profiles derived from a single sample; this significantly reduces the fitting uncertainties in the parameters μ and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.gif" overflow="scroll"〉〈mrow〉〈mover accent="true"〉〈mrow〉〈mi〉σ〈/mi〉〈msub〉〈mi〉φ〈/mi〉〈mn〉0〈/mn〉〈/msub〉〈mi〉t〈/mi〉〈/mrow〉〈mo stretchy="true"〉¯〈/mo〉〈/mover〉〈/mrow〉〈/math〉. The long-term relative bleaching rate of the IR〈sub〉50〈/sub〉, MET-pIRIR〈sub〉110〈/sub〉, MET-pIRIR〈sub〉170〈/sub〉 and MET-pIRIR〈sub〉225〈/sub〉 signals were evaluated by comparing the ratios of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.gif" overflow="scroll"〉〈mrow〉〈mover accent="true"〉〈mrow〉〈mi〉σ〈/mi〉〈msub〉〈mi〉φ〈/mi〉〈mn〉0〈/mn〉〈/msub〉〈mi〉t〈/mi〉〈/mrow〉〈mo stretchy="true"〉¯〈/mo〉〈/mover〉〈/mrow〉〈/math〉 derived from fitting of luminescence-depth profile. The IR〈sub〉50〈/sub〉 signal, MET-pIRIR〈sub〉110〈/sub〉 and MET-pIRIR〈sub〉170〈/sub〉 bleached tens, ∼5, and 2 times faster than the MET-pIRIR〈sub〉225〈/sub〉 signals, respectively. These results highlight the potential and challenges in using rock surface luminescence methods as a viable dating tool for exposure ages.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 17 April 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): D.E. Folley, M.L. Chithambo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The influence of annealing on the main thermoluminescence glow-peak of natural quartz is reported. For comparison, results from un-annealed quartz are included. The glow-curve measured at 1 °Cs〈sup〉−1〈/sup〉 after beta irradiation to 50 Gy revealed six peaks each for quartz annealed at 800 °C for 1 h and the un-annealed sample. The main peak in both quartzes was observed at 72 °C. This report focusses on kinetic analysis of the main peak. The analysis was carried out using various methods consisting of the initial rise, whole glow-peak, peak shape, variable heating rate and phosphorescence-based methods. The activation energy obtained using the various methods ranges between 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mn〉0.91〈/mn〉〈mo〉±〈/mo〉〈mn〉0.01〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mtext〉eV〈/mtext〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.gif" overflow="scroll"〉〈mrow〉〈mn〉1.19〈/mn〉〈mo〉±〈/mo〉〈mn〉0.03〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mtext〉eV〈/mtext〉〈/mrow〉〈/math〉 for the annealed sample and between 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.gif" overflow="scroll"〉〈mrow〉〈mn〉0.93〈/mn〉〈mo〉±〈/mo〉〈mn〉0.01〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mtext〉eV〈/mtext〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.gif" overflow="scroll"〉〈mrow〉〈mn〉1.26〈/mn〉〈mo〉±〈/mo〉〈mn〉0.12〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mtext〉eV〈/mtext〉〈/mrow〉〈/math〉 for the un-annealed sample. The result suggests that annealing has little effect on the activation energy. The luminescence intensity decreased with heating rate in the un-annealed sample in a manner suggestive of thermal quenching. In contrast, the dependence of intensity on heating rate in the annealed sample is influenced by the dose the sample is irradiated to. Whereas thermal quenching was noted for a dose of 50 Gy in the un-annealed sample, the annealed sample showed evidence of thermal quenching at a low dose of 3 Gy with the opposite effect when irradiated to 50 Gy. The activation energies of thermal quenching were found as 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.gif" overflow="scroll"〉〈mrow〉〈mn〉0.89〈/mn〉〈mo〉±〈/mo〉〈mn〉0.06〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mtext〉eV〈/mtext〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si6.gif" overflow="scroll"〉〈mrow〉〈mn〉0.99〈/mn〉〈mo〉±〈/mo〉〈mn〉0.02〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mtext〉eV〈/mtext〉〈/mrow〉〈/math〉 for the un-annealed and annealed samples respectively. We ascribe the apparent dependence of thermal quenching on dose in the annealed sample to competition between radiative and non-radiative transitions at the recombination centre.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 29 May 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Vicki Hansen, Andrew Murray, Kristina Thomsen, Mayank Jain, Martin Autzen, Jan-Pieter Buylaert〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The ability to deliver accurate and precise calibration doses is a central part of all trapped charge dating methods. Usually, the radiation source (α, β, X-ray) used to deliver these doses is, in turn, calibrated against an absolutely known reference source (usually a γ source) and many laboratories make use of Risø calibration quartz for this purpose. We have previously described this material in detail (Hansen et al., 2015) and discussed the over-dispersion (OD) of 3.2 ± 0.3% in calibrated dose rate observed over 16 years. This dispersion highlights the danger of relying on individual calibrations, and is clearly undesirable. Here we continue our investigation into providing reliable calibration materials for trapped electron dating. A comparison of the apparent quartz β source dose rates shows that there is no significant dependence on the geological source of the quartz. However the β dose rate decreases by 25% with increasing grain size from about 100 μm to 1 mm, and backscatter leads to a dose rate increase of ∼1% per unit atomic number of the substrate. It is concluded that, for the multi-grain aliquots used in this study, the contributions to dose rate variability from grain size and substrate variations are likely to be negligible. Nevertheless there may be a practical advantage in using a high Z substrate because of the higher dose rate. Finally we test the measured to given dose (dose recovery) ratio for five heated feldspar samples and use the pIRIR〈sub〉290〈/sub〉 signal for β source calibration; surprisingly this gives an apparent β dose rate 15% lower than that to quartz despite their almost identical stopping power and mass absorption characteristics. Our results are discussed in terms of their significance for reproducibility and accuracy of β dose-rate estimates.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Svenja Riedesel, Georgina E. King, Amit Kumar Prasad, Raju Kumar, Adrian A. Finch, Mayank Jain〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We constrain parameters that determine thermal stability of the infrared stimulated luminescence (IRSL) signal in a suite of 13 compositionally different feldspar samples by optical probing. We focus specifically on the excited and ground state of the principal trap and the width of the sub-conduction band-tail states. Excitation spectra measured at room temperature result in approximate trap depth of about 2.04 eV and the excited state energy at 1.44 ± 0.02 eV, irrespective of feldspar composition for the sample's measured here. Fitting the non-resonant rising continuum of the excitation spectra suggests that the width of the band-tail states accessible from the ground state of the trap (ΔE) ranges from 0.21 to 0.47 eV at room temperature between the different samples. Photoluminescence measurements are used to constrain the full sub-conduction band-tail width (Urbach width, E〈sub〉u〈/sub〉) using the excitation-energy-dependent emission (EDE), resulting in values ranging from 0.26 to 0.81 eV. While the depth of the principal trap and its main excited state seem to be independent of feldspar composition, the difference between ΔE and E〈sub〉u〈/sub〉 seems to be related to sample K-content.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Pierre Gillet, Mélodie Munier, Nicolas Arbor, Fanny Carbillet, Ziad El Bitar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Purpose〈/h6〉 〈p〉The aim of this work is to compare the energy response of a scintillating fiber to that of standard detectors used for dose monitoring in Computed Tomography (CT) and confirm the validity of Plastic Scintillating Detectors in CT dosimetry. We also seek to model the scintillating fiber response in realistic irradiation conditions for future applications on a complete dose measurement system. For this, we have modeled an X-ray generator emission and validated the model using its measured X-rays spectrum.〈/p〉 〈/div〉 〈div〉 〈h6〉Materials and methods〈/h6〉 〈p〉Irradiations were performed in an X-ray generator at voltage varying from 80 to 140 kV. The Plastic Scintillating Detector (PSD) was compared with a pencil ion chamber and Thermo-Luminescent Detectors (TLD).〈/p〉 〈p〉Monte Carlo simulations of each detector response were compared to measurements in order to validate the simulation in a simple case.〈/p〉 〈/div〉 〈div〉 〈h6〉Results〈/h6〉 〈p〉The Monte Carlo simulations reproduced accurately the response of each detector with less than 3% and 5% of difference for the ion chamber and the TLDs respectively. When comparing the PSD with the two standard detectors, we observed that while the plastic scintillator detector and the ion chamber responses presented less than 5% discrepancy, they both were very different than TLDs response on the whole investigated energy range. The Monte Carlo simulation of the PSD reproduced accurately the response of the plastic scintillating detector with less than 3% of difference.〈/p〉 〈/div〉 〈div〉 〈h6〉Conclusion〈/h6〉 〈p〉The X-ray spectrum has been accurately measured which allowed to successfully reproduce the energy response of the PSD using Monte Carlo simulations. Although this study proved that the scintillating fibers energy response is appropriate for CT dose measurement, further experiments must be performed in clinical conditions.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 2 May 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Sebastian Kreutzer, Loïc Martin, Stéphan Dubernet, Norbert Mercier〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Infrared radiofluorescence (IR-RF) of K-feldspar is an alternative luminescence dating approach to infrared luminescence (IRSL). The application of IR-RF on coarse grain K-feldspar untreated with HF requires knowledge of the IR-RF α-efficiency. We present IR-RF α-efficiency measurements performed on four natural fine grain (4–11 μm) K-feldspar samples and test whether the α-efficiency is similar to that reported for IRSL on polymineral fine grain. The samples originate from Late and Middle Pleistocene aeolian sediment records in France and Germany. The fine grain fraction was obtained by crushing grains of diameter 90–200 μm. The natural signal was reset by optical bleaching at 70 °C using a solar simulator. The α-irradiation was carried out on a home-made α-irradiator, equipped with a 〈sup〉241〈/sup〉Am source. For our irradiation setup, energy spectra were simulated using 〈em〉Geant4〈/em〉 to estimate the particle energy of the incident and exiting α-particles after passing a K-feldspar target. The α-flux induced IR-RF signals show a (super) linear dose-response up to 9.5 × 10〈sup〉9〈/sup〉 (integrated α-flux on the sample). The results indicate no significant difference between the IR-RF α-efficiency of the four samples. An averaged central 〈em〉S〈/em〉〈sub〉〈em〉α〈/em〉〈/sub〉 -value of 9.26 ± 1.62 μGy/(10〈sup〉3〈/sup〉α cm〈sup〉−2〈/sup〉) (corresponding 〈em〉a〈/em〉-value: 0.067 ± 0.012) was obtained from 84 measurements of all four samples. Our results are similar to 〈em〉a〈/em〉-values reported for IRSL on polymineral fine grain. We finally discuss how the central 〈em〉S〈/em〉〈sub〉〈em〉α〈/em〉〈/sub〉-value can be applied to calculate the β-equivalent α-dose rate of coarse grain mineral extracts.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): K.J. Thomsen, M. Kook, A.S. Murray, M. Jain〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉It is desirable to be able to establish the relationship between the spatial distribution of luminescence and chemical composition/mineralogy. This is especially true in complex, heterogeneous samples such as solid coarse-grained rock slices and separated feldspar grains, where the internal dose rate is very dependent on the effective size of luminescent regions of the sample. The addition of spectral information would then help to give further insights into luminescence production mechanisms.〈/p〉 〈p〉A high sensitivity imaging attachment to the Risø TL/OSL Reader for investigating the spatial distribution of OSL and TL from natural and artificial phosphors has recently been developed (Kook et al., 2015). When combined with a Bruker μ-XRF facility and a high sensitivity spectrometer attachment, it is possible to investigate the relationship between the spatial distribution of luminescence, the distribution of chemical composition/mineralogy and the associated excitation and emission spectra.〈/p〉 〈p〉Here laboratory measurements undertaken using solid rock samples are presented and the observed relationships and their dosimetric implications are discussed.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): A. Timar-Gabor〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Different optically stimulated luminescence (OSL) single aliquot regenerative (SAR) saturation characteristics have been previously reported for quartz of diverse grain sizes. This preliminary electron spin resonance (ESR) study documents on paramagnetic signals in natural sedimentary quartz extracts of different grain sizes (4–11 μm, 63–90 μm, 90–125 μm, 125–180 μm, 180–250 μm) extracted from loess and sand samples that are amendable to OSL and ESR dating. Spectra recorded at room temperature and low power (〈1 mW) are dominated by the E〈sub〉1〈/sub〉’ centre, whose intensity in natural samples was found to decreases with increasing grain size. The signature of titanium centre could not be detected in fine (4–11 μm) quartz. For coarse fractions (〉63 μm) titanium-lithium [TiO〈sub〉4〈/sub〉/Li〈sup〉+〈/sup〉]〈sup〉0〈/sup〉 signals increase with increasing grain size. Aluminium-hole ([AlO〈sub〉4〈/sub〉]〈sup〉0〈/sup〉) signals are observed in all natural and laboratory irradiated investigated samples when spectra are recorded at low temperature (90 K). The intensity of these signals appears to decrease with increasing grain size, however, room temperature measurements show that these signals are highly interfered by a variety of signals tentatively attributed to peroxy (g ≈ 2.007 and g ≈ 2.004) with significantly higher intensities in fine grains (4–11 μm). A decrease of their intensity is reported when grain size increases and partial evidence that these defects are preferentially located in damaged regions of the grains is presented. A dose dependent paramagnetic signal at g ≈ 2.011 was detected only in 4–11 μm quartz. The stronger signature of the [TiO〈sub〉4〈/sub〉/Li〈sup〉+〈/sup〉]〈sup〉0〈/sup〉 signals in larger grains coupled with the weaker signals of peroxy signals interfering with [AlO〈sub〉4〈/sub〉]〈sup〉0〈/sup〉 signal measurement is suggesting that coarser fractions should be preferred for conventional ESR dating using aluminium-hole and titanium signals. The understanding of the implication of these defects in OSL dating alongside with their concentration dependency on grain size requires further investigations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): Jhonny Rojas, Daniel Palacios, Patrizia Pereyra, Bertin Pérez, Laszlo Sajo Bohus, María Elena López〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉One way to estimate the calibration factor (CF) of an LR-115 detector within a diffusion chamber by Monte Carlo (MC) simulation requires as input parameters the energy window (Δ〈em〉E〈/em〉), the dependence of critical angle with energy [〈em〉θ〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉 = 〈em〉f〈/em〉(〈em〉E〈/em〉)] or mean critical angle (〈〈em〉θ〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉〉), and the air fraction of 〈sup〉218〈/sup〉Po atoms (〈em〉f〈/em〉〈sub〉〈em〉1〈/em〉〈/sub〉). Using simulated tracks and MC techniques, it was demonstrated that 〈〈em〉θ〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉〉 can replace 〈em〉θ〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉 = 〈em〉f〈/em〉(〈em〉E〈/em〉) relatively accurate. Results of numerical examples validate the correct performance of developed MC code. A semi-empirical approach to estimating the parameters 〈em〉E〈/em〉〈sub〉min〈/sub〉, 〈em〉E〈/em〉〈sub〉max〈/sub〉, 〈〈em〉θ〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉〉, and 〈em〉f〈/em〉〈sub〉〈em〉1〈/em〉〈/sub〉 is presented. The method is based on the calculation of the CFs by means of MC simulations (〈em〉S〈/em〉〈sub〉〈em〉sim〈/em〉〈/sub〉) for the range of expected input parameters values and their comparison with the experimental CF (〈em〉S〈/em〉〈sub〉〈em〉exp〈/em〉〈/sub〉). Parameters that minimized the deviations between 〈em〉S〈/em〉〈sub〉〈em〉exp〈/em〉〈/sub〉 and 〈em〉S〈/em〉〈sub〉〈em〉sim〈/em〉〈/sub〉 were obtained through successive iterations. 〈〈em〉θ〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉〉 was the parameter with the most marked and differentiated tendency to converge. The energy window and mean critical angle for our etching conditions, track counting method, and environmental conditions during exposure of LR-115 detectors were [1.5 ± 0.3, 4.0 ± 0.2]MeV and (56.1 ± 6.6)°, respectively. The air fraction 〈em〉f〈/em〉〈sub〉〈em〉1〈/em〉〈/sub〉 was found to be 0.1 for most of the used diffusion chambers. The comparison of radon concentrations obtained with the reference and test monitors, using in the latters the CFs simulated with the mean values of found parameters, demonstrate that the proposed method is applicable if uncertainties around 20% are accepted.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): Sandipan Dawn, Rupali Pal, A.K. Bakshi, R.A. Kinhikar, Kishore Joshi, S.V. Jamema, Abdul Haneefa, T. Palani Selvam, D.D. Deshpande, D. Datta〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A comprehensive study on the evaluation of in-field photo-neutron and electro-neutron dose equivalent (H〈sup〉∗〈/sup〉(10)), neutron fluence and energy spectra was carried out using passive detectors such as PADC and TLDs and supplemented with Monte Carlo simulation. The studies were carried out for VARIAN LINAC models NovalisTx and TrueBeam. Measurements on the influence of beam parameters such as field size, wedge angle, depth in phantom, photon and electron energies and variation of neutron dose equivalent with distance from isocentre were studied. Further, influence of beam flattening filter for 10 MV photon beam in TrueBeam was included. Simulation using FLUKA Monte Carlo code for the generation of neutron lethargy spectra and spectra weighted H*(10) at different depths of phantom was performed. Influence of different components of LINAC head on neutron spectra was also simulated for 15 MV photon beam with and without flattening filter.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): A. Vedda, M. Fasoli〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉This review paper provides a description of direct recombination processes between carriers from traps to luminescent centers, involving the occurrence of a tunneling mechanism between their space-correlated localized electronic levels.〈/p〉 〈p〉The experimental evidences that allow to recognize tunneling recombination in phosphorescence time decay and thermoluminescence experiments are first outlined, and compared with those characteristic of recombination processes involving the transfer of carriers in the delocalized bands prior to their recombination. Simple explanations are also proposed for the phenomenological observations in both athermal and thermally assisted tunneling processes.〈/p〉 〈p〉The importance of such recombinations in three material classes – scintillators, persistent phosphors, and dosimeters, is then outlined and discussed in relation to the material requirements in their distinct application fields. For each application, numerous literature examples are reported. Finally, the paper is complemented by a brief illustration of literature investigations describing experimental evidences of direct trap-center recombination different from tunneling, mostly based on the inspection of emission spectra and thermoluminescence glow curve shapes.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): V. Chopra, S.J. Dhoble, Karan K. Gupta, A. Singh, A. Pandey〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermoluminescence (TL) properties of Li〈sub〉2〈/sub〉B〈sub〉4〈/sub〉O〈sub〉7〈/sub〉:Cu material prepared by combustion method and irradiated with 3 MeV of proton beam have been studied. It is found that the nanophosphor shows a linear TL response over a wide range of absorbed dose (1 kGy–10〈sup〉3〈/sup〉 kGy) for 3 MeV proton beam. Activation energy (E) and Order of kinetics (b), are determined using GCCD (glow-curve convolution deconvolution) functions by generating the theoretical curve that is in good match with the experimental glow curve. Further Ion beam parameters are analyzed using Monte-Carlo simulation-based SRIM-2013 code. It is analyzed that the simple glow curve structure, wider linear TL response of Li〈sub〉2〈/sub〉B〈sub〉4〈/sub〉O〈sub〉7〈/sub〉:Cu and its low fading makes it a good candidate to be used as an effective proton beam TL dosimeter for the treatment of cancer.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Pengfei Wang, Xue Wang, Yun Ling, Mao Wang, Siyuan Ding, Wenhao Shen, Zhong Wang, Yugang Wang, Feng Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉12-μm-thick 〈em〉polyethylene terephthalate〈/em〉 (PET) track membranes with sub-nanometer pores fabricated with the newly developed track-UV technique without chemical etching showed ultrahigh selective ionic transport yet low permeability. We discovered that the permeability of these track membranes were irreversibly improved by two to three orders of magnitude via heat treatment. Meanwhile, these heat-treated track membranes maintained the high selectivity of ions. Our experimental results suggest heat treatment on the track membranes with sub-nanometer pores could provide a reliable and controllable way to enlarge nanopore size, and bring the track membrane to promising applications on ion separations, water purification, diaphragm material and so on.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 13 March 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): M.C. Meyer, L.A. Gliganic, M. Jain, R. Sohbati, D. Schmidmair〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Luminescence surface exposure dating is a newly developed geochronological technique that allows the age of geological or archaeological rock surfaces to be accurately constrained. This dating method requires measuring and calibrating the depth-dependent luminescence signal below an exposed surface and relies on the assumption that neither the shape of the daylight spectrum nor the light attenuation change significantly with depth into the rock. However, lithologies with mm-scale heterogeneity in their mineral distribution or those lacking high sensitivity quartz present a challenge, partly because light attenuation with depth is not necessarily constant in such samples. Addressing these challenges is important for further development of the luminescence surface exposure dating technique.〈/p〉 〈p〉Here we investigate the shape of luminescence-depth profiles in lithologies revealing complex fabrics such as coarse-grained granitic gneisses or gneisses with distinct planar metamorphic layering. We also present luminescence-depth profiles from quartzite, a lithology that appears – at first glance – highly homogenous. We find that the spatial distribution of opaque mineral phases in the metamorphic samples and precipitation of iron hydroxides in the quartzite strongly influence the 3-dimensional transparency and, consequently, the light attenuation with depth, and are the main cause for the observed scatter in the OSL- and IRSL-depth profiles in our samples. The data suggest that for rocks of heterogeneous lithology (i) close petrographic analysis of luminescence-depth profiles are required to ensure that the cores used for calibration have similar mineralogical composition (and thus light attenuation with depth) to those used to calculate a luminescence rock surface exposure age, and that (ii) RGB depth profiles appear to provide a useful semi-quantitative tool for such analysis.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 8 May 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): N. Meriç, E. Aşlar, E. Şahiner, Y.K. Kadioğlu, G.S. Polymeris〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Durango apatite is a material that exhibits very strong athermal fading (AF) of luminescence signal. In this study, the EPR signals of natural Durango apatite in various different grain dimensions (ball milled for various durations up to 48 h and microscale grain size) were studied. The obtained EPR signal at room temperature yielded three different components with 〈em〉g〈/em〉 values 2.0534 (hole center), 2.0398 (hole center) and 1.9920 (electron center). These components were observed for the reference grain size fraction of 100–180 μm; however, prolonged ball milling erases the two hole centers. The behaviour of all obtained components was investigated by step annealing processes (a) between room temperature and 400 °C in steps of 25 °C for 5 min and (b) between 400 °C and 1100 °C, in steps of 100 °C for 1 h. The EPR component with g value 1.9918 was almost totally removed until 1100 °C, while those with g values 2.0534, 2.0398 were erased after annealing at 500 °C and 400 °C respectively. The fading of EPR components was investigated for each ball milling (BM) and microscale grain size independently, at different storage times between 0 and 1000 min. Based on the results of fading and step annealing studies, the EPR component with 〈em〉g〈/em〉 value 2.0398 could be directly correlated to the main dosimetric TL trap, while the component with 〈em〉g〈/em〉 value 1.9920 appears to be responsible for TA – OSL signal for microscale grain size apatite, corresponding thus to a very deep trap. The behaviour of remnant EPR signal versus storage time could be successfully described by equations based on quantum mechanical tunnelling mechanism.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): Wagner Massayuki Nakasuga, Carlos Alberto Tello Saenz, Eduardo Augusto Campos Curvo, Julio Cesar Hadler Neto, Sandro Guedes, Rosana Silveira Resende〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Along the years, etching for fission tracks was a major issue in the development of the epidote fission track dating. It was not a consensus in the scientific community. As an attempt to mitigate it, we present a novel etching protocol (HF 40% at 15 °C for 80 min) and test it in ten different natural samples etched with HF 40% at 15 °C for 80 min (nine epidotes and one clinozoisite). The samples had their chemical compositions determined, forming a database for epidote chemical compositions. Fission tracks were observed in five samples. The uranium content in the remaining four samples was too low and hence tracks could not be observed. Further analyses, Raman and uranium concentration, confirm this observation. Fission tracks were not observed in clinozoisite sample. The proposed etching protocol showed to be less hazardous and efficient to etching fission tracks in epidote.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Jessica M. Fagerstrom, Larry A. DeWerd, Benjamin Palmer, Wesley S. Culberson〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This work sought create a set of prototype modulated orthovoltage stereotactic radiosurgery (SRS) cones, and to perform a dosimetric characterization of the prototypes. Four radiosurgical cone collimators (with cone diameters of 5 mm, 6 mm, 8 mm, and 10 mm) were built for use with an orthovoltage unit, along with epoxy-infiltrated bonded tungsten filters designed to shape the resulting dose distributions. Dosimetry measurements were performed using radiochromic film in a water phantom for both filtered and unfiltered cones at depths of 2.5 cm, 5.0 cm, and 7.5 cm. Films were scanned using a flatbed scanner and the beam profiles were analyzed. Extracted beam profiles validated the ability to optimize dosimetric results based on desired dose distributions, where for this work the goal distributions were rectangular functions. Radiochromic film measurements of dose distributions in water confirmed that the prototypes were able to achieve distributions approaching rectangular functions at depth, as determined by penumbra and flatness statistics. A prototype set of novel, modulated orthovoltage SRS filtered cones was successfully constructed, and a full dosimetric characterization was completed in water. In all configurations, filtered, optimized cones were able to achieve distributions more closely approaching the goal distributions compared to open cones.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): Chun-Hui Hsing, I-Chun Cho, Tsi-Chian Chao, Ji-Hong Hong, Chuan-Jong Tung〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The potential radiosensitizing effects of gold nanoparticles (GNPs) in radiation therapy have been extensively studied. GNPs loaded in the tumor produce a large number of low-energy secondary electrons which contribute to the local dose enhancement and elevate the relative biological effectiveness (RBE). Thus GNP enhanced responses in 〈sup〉192〈/sup〉Ir, a widely used brachytherapy source, are the subject of interest. These radiosensitizing effects can be examined through comparisons between microdosimetric spectra of secondary electrons resulting from the 〈sup〉192〈/sup〉Ir in the presence and absence of GNPs in cells. Measurements of single-event lineal energy spectra give indications of a relative therapeutic advantage. In the present work, a mini tissue equivalent proportional counter (TEPC) was constructed to measure the microdosimetric spectra in cells containing and without GNPs for 〈sup〉192〈/sup〉Ir source. A plug, either contained a 50 nm-thick gold foil coated on its inner surface or without the foil, was inserted into the TEPC wall during measurements. Analyses of the measured un-normalized and normalized dose lineal energy spectra provided information on the enhancements in absorbed dose and RBE. The dose enhancement was 1.27 and 1.37 for 1 and 0.5 μm-diameter sites, respectively. The increase in dose enhancement with decreasing site diameter revealed the sharp fall-off in the local dose enhancement. Applying the biological weighting function method, the RBE enhancement was 1.32 based on the lineal energy spectra of 1 μm site.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): V. Anechitei-Deacu, A. Timar-Gabor, K.J. Thomsen, J.-P. Buylaert, M. Jain, M. Bailey, A.S. Murray〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉There is evidence that optically stimulated luminescence (OSL) dating of quartz using the single-aliquot regenerative-dose (SAR) protocol underestimates the equivalent dose (D〈sub〉e〈/sub〉) for paleodoses above 100–200 Gy. Additionally, ‘infinitely’ old samples found not to be in laboratory saturation were reported. We present single and multi-grain SAR-OSL investigations for a coarse-grained (180–250 μm) quartz sample extracted from loess collected below the Brunhes/Matuyama transition at the Roksolany site (Ukraine). The sample was dated to more than 1000 ka by electron spin resonance using a multi center approach (Al and Ti signals), confirming that the D〈sub〉e〈/sub〉 (∼2000 Gy) falls beyond the limit of standard OSL D〈sub〉e〈/sub〉 measurement techniques. However, the natural signal measured using multi-grain aliquots of quartz was found to be below the laboratory saturation level. A comparison was made between synthetic dose response curves (DRCs) generated from single-grain and multi-grain aliquot data, respectively; the natural signal was found to be closer to the latoratory saturation level (92%) in the case of the single-grain synthetic DRC than for the multi-grain synthetic DRC where the signal was 86% of the saturation level. This difference could not be attributed to stimulation with different wavelengths, i.e. blue and green light stimulation for multi and single-grain measurements, respectively. By analysing synthetic data obtained by grouping grains according to their brightness, it was observed that brighter grains give a natural signal closer to the laboratory saturation level. This trend was confirmed for multi-grain aliquot data. Based on these findings we infer that variability in the contribution from populations of grains with different levels of brightness may represent a controlling factor in the closeness of the natural signal to laboratory saturation level for infinitely old samples.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): Molham M. Eyadeh, Khalid A. Rabaeh, Tariq F. Hailat, Mohammad Y. Al-Shorman, Feras M. Aldweri, Haitham M. Kanan, Samer I. Awad〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel radiosensitive composition of radiochromic gel dosimeter based on Fricke polyvinyl alcohol (PVA), Methylthymol blue dye (MTB), and chemical cross-linking agent glutaraldehyde (GTA) is presented and studied. Due to the MTB-PVA-GTA dosimeter having a transparent solid cross-linked formulation, this new composition can be used with 2D and 3D optical detection instruments. It can be scanned at higher wavelengths compared to conventional Xylenol orange (XO) containing gel (620–625 nm 〈em〉vs.〈/em〉 585–587 nm). The transparent chemically cross-linked dosimeter was evaluated using optical detection methods; spectrophotometry and 2D optical imaging system of charge-coupled-device (CCD) camera with a uniform red light-emitting-diode (LED) array source. Additionally, the dosimeter showed a promising high dosimetric sensitivity of 0.077 a.u Gy〈sup〉−1〈/sup〉, a low auto-oxidation rate of 0.017% per hour, and a low diffusion coefficient of 0.150 mm〈sup〉2〈/sup〉 h〈sup〉−1〈/sup〉. The measured sensitivity was higher than the previously reported values of other PVA-gel based radiochromic dosimeters (MTB-PVA, XO-PVA, XO-PVA-GTA), and similar to Fricke-MTB-gelatin system. The diffusion coefficient of the presented dosimeter is significantly lower than that of the natural polymer-containing gels.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): Hyoungtaek Kim, Min Chae Kim, Jungil Lee, Insu Chang, Seung Kyu Lee, Jang-Lyul Kim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Phototransferred thermoluminescence (PTTL) characteristics of LiF:Mg,Cu,Si, developed by the Korea Atomic Energy Research Institute, are presented as part of a simple and reliable method for dose re-evaluation that is compatible with routine personal dosimetry services. A 4.5 mm diameter 0.8 mm thick pellet-type thermoluminescence dosimeter (TLD) was used after dual-step thermal annealing at 300 °C for 10 min, and then at 260 °C for 10 min, in order to obtain thermal stability. For optimal UV illumination, samples were placed under a 254 nm ultraviolet (UV) lamp for 90 min. The PTTL signal was only lower than 2% that of the TL because of low residual signals in high-temperature deep traps. The difference of the PTTL signals between samples appeared up to two times, indicating high variation in the charge density of the deep traps between samples. Various thermal treatments were performed after each PTTL measurement to remove the residual PTTL signal. UV exposure at 250 °C for 20 min fully reset the residual PTTL signals to the same level as that after dual-step annealing. No degradation of the TL peak from repeated thermal treatments was observed until after the eighth treatment when a decrease was noticeable. The measured dose response of PTTL in the range of 1.14–51.3 mGy showed good linearity. The zero dose and minimal detectable dose of the PTTL were 1.36 ± 0.51 mGy and 1.53 mGy, respectively. The attenuation of the PTTL signal resulting from successive TL measurements was recorded to provide a correction factor for quarterly recorded TL measurements applicable to the dose re-evaluation of TLDs in routine personal dosimetry services.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 25 May 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): A. Chruścińska, A. Szramowski〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The methods of optically stimulated luminescence (OSL) measurements used until recently applied optical stimulation at a constant temperature, with a constant stimulation energy and a constant or linearly increased flux of stimulation photons. During such stimulation the optical cross-section of traps is invariable and it is hard to separate the signals of different origins. It was shown recently that the selective optical emptying of traps is much easier when the optical cross-section is changed during the stimulation. Due to the dependence of the optical cross-section on temperature advantageous changes in this trap parameter can be induced by increasing the sample temperature during optical stimulation. Such a method can be called thermally modulated OSL (TM-OSL). When the experimental conditions are properly selected the TM-OSL curve has the form of a peak. The shape and position of this peak are uniquely determined by the trap parameters and, therefore, curve analysis can be used to estimate the optical depth of the trap (photoionization threshold) and the strength of electron-lattice coupling. These parameters define traps unambiguously and allow a direct correlation of the traps active in the OSL and TL processes to be made. The position of the TM-OSL peak on the temperature axis depends greatly on the stimulation energy, the heating rate and the photon flux used for optical stimulation, so these experimental factors can be used to separate the individual OSL components. This work focuses on the selective detection of the fast component of the quartz OSL signal. The traps responsible for the fast OSL component can be depopulated by light with the wavelength of 620 nm, which is far longer the usual 470 or 530 nm used in OSL measurements of quartz. The results of such experiments, when supported by computer simulations of the thermally modulated OSL process, allow the value of 3 eV to be estimated for the optical depth of traps responsible for the fast OSL component in quartz.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): Tamon Kusumoto, Ziad EL Bitar, Shogo Okada, Pierre Gillet, Nicolas Arbor, Masato Kanasaki, Yutaka Mori, Keiji Oda, Abdel-Mjid Nourreddine, Hisaya Kurashige, Michel Fromm, Pierre Cloutier, Andrew D. Bass, Léon Sanche, Satoshi Kodaira, Rémi Barillon, Tomoya Yamauchi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The detection threshold of poly(allyl dyglycol carbonate), PADC, for C ions is determined as 55 eV/nm in stopping power, which is significantly higher than that for proton and He ions. The stopping power is not a universal parameter for expressing the detection threshold of PADC. A new physical parameter of Radial Electron Fluence around Ion Tracks, 〈em〉REFIT〈/em〉, is proposed to describe the detection threshold of PADC. It is defined as the number density of electrons passing through the surface of a cylinder of a certain radius that is co-axial with the trajectory. Furthermore, preliminary calculations are presently being performed using the Monte Carlo simulation code of Geant4-DNA. The values of the 〈em〉REFIT〈/em〉 at the detection thresholds for each ion are of the same order. Several issues affecting implementation of the 〈em〉REFIT〈/em〉 paramter are discussed. These include the effects of impact parameter relating to the initial locations of secondary electrons, the effects of electron attachment below the cut off energy of 7.4 eV and the necessity of a more physically realistic medium than water for Monte Carlo simultaions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 July 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): A.N. Nyirenda, M.L. Chithambo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The spectral emission study of the radioluminescence (RL) measured from carbon-doped aluminium oxide (〈em〉α〈/em〉-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉:C) at various temperatures between 30 and 300〈sup〉∘〈/sup〉C is reported. The energy-resolved RL emission spectra measured at room temperature show seven gaussian emission bands centred at 1.75, 1.79, 1.85, 2.22, 2.96, 3.72 and 4.44 eV. The 2.96-eV emission, associated with F-centres, is the primary RL emission whereas the narrow (R-line) emission centred at 1.79 eV, associated with Cr〈sup〉3+〈/sup〉 impurity ions, is the most intense secondary emission. However, the intensity of 1.79-eV emission decreases with repeated RL measurements. The central emission energy for F-centres is constant throughout the temperature range of investigation. The full width at half maximum (FWHM) for the F-centre emission band increases with temperature whereas the F-centre peak intensity exhibits thermal quenching behaviour at temperatures above 160〈sup〉∘〈/sup〉C. On the other hand, the emission energy for the R-line emission of Cr〈sup〉3+〈/sup〉 is constant for temperatures between 30 and 160〈sup〉∘〈/sup〉C, whereas its peak intensity generally decreases with temperature. F-centres experience strong-coupling in their crystallographic sites with estimated electron-lattice coupling parameters of S = 5.0 ± 0.9, 〈em〉E〈/em〉〈sub〉〈em〉p〈/em〉〈/sub〉 = 0.079 ± 0.008 eV and 〈em〉ν〈/em〉 = 1.91 × 10〈sup〉13〈/sup〉 Hz where S, 〈em〉E〈/em〉〈sub〉〈em〉p〈/em〉〈/sub〉 and 〈em〉ν〈/em〉 are the Huang-Rhys factor, the phonon energy and the phonon frequency, respectively. The RL spectra recorded while ramping the temperature of a sample at a constant rate have been compared against conventional TL spectra.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 April 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): G.S. Polymeris, E. Şahiner, Y.K. Kadioğlu, N. Meriç〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A rapidly decaying curve shape, similar to the conventional optically stimulated luminescence (OSL) curve, is observed when thermally assisted (TA –) OSL signal from quartz is measured at a steady elevated temperature. In some cases, a peculiar shape consisting of one flat signal is yielded. The effects of thermal assistance and dose applied on the features of this peculiar type of curve were studied using quartz samples collected from Anatolia, Turkey. The results indicated the absence of the initial rapidly decaying part of the conventional OSL for this peculiar curve of TA-OSL for all stimulation temperature and dose ranges attributed within this work. The intensity of the flat decay curve signal was observed to be dependent on both stimulation temperatures and doses. It was demonstrated that for this specific signal, thermally assisting activation energy of almost 1 eV stands as a prevalent feature, indicating that this TA – OSL signal with flat shape originates from very deep traps with activation energy under the conduction band of the order of 3 eV. This suggests that such a trap could provide signal with adequate stability for dating back to a million years, or even more. The dose response linearity for high attributed doses strongly supports the application of Single Aliquot Regenerative TA – OSL for equivalent dose estimations. However, the high recuperation values, of the order of 30%, indicating possible underestimation of the equivalent doses, along with recycling ratio values of around 1.25, stand as drawbacks that limit the use of such TA – OSL signal in single aliquot regenerative protocols for equivalent dose estimations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 12 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Michael Discher, Barbara Mauz, Loïc Martin, Julie A. Durcan, Georgina E. King, Evangelos Tsakalos, John Christodoulakis, Andreas Lang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Accurate determination of the environmental radiation dose-rate is crucial for dosimetric dating methods. Two approaches for dose-rate estimation are currently employed: (1) calculating and summing up individual dose-rate components, including propagation of uncertainties and (2) simulating the radiation field and calculating the absorbed dose using a Monte Carlo approach. Here we compare dose-rate estimation using the two aforementioned approaches, applied to six sedimentary quartz samples with differing radionuclide concentrations, chemical composition, grain-size distribution and water content and to one heterogeneous archaeological sample. For approach (1) two web-based, freely accessible calculators, “Dose-Rate calculator” (DRc), “Dose Rate and Age Calculator” (DRAC) and a bespoke spreadsheet were used. For approach (2) DosiVox, a Geant4 Monte Carlo simulation toolkit was employed which allows the definition of material properties such as chemical composition, density and porosity in addition to radionuclide concentrations and water content in a three dimensional geometry. The sensitivity of dose rate to material properties, usually assumed to be constant over the burial time scale, was also tested.〈/p〉 〈p〉The results obtained using the three dose-rate calculators for sedimentary quartz samples are consistent within uncertainties, mainly because the conversion and correction factors are all taken from the same references. Comparing these results with those obtained from DosiVox simulations show grain-size dependent dose-rate differences, caused by the charge build-up and attenuation of the irradiated grain-size fraction. Moreover, it reveals that the effect of porosity and moisture on dose rate is grain-size dependent. For the heterogeneous archaeological sample the total dose rate determined by a calculator is inaccurate for the alpha- and too precise for the beta dose-rate. We conclude that the standard approach to dose-rate estimation is robust and that DosiVox is an important diagnostic tool for samples originating from complex environments.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 March 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Johannes Friedrich, Sebastian Kreutzer, Christoph Schmidt〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Thermal quenching is a well-known phenomenon in quartz, which describes the decrease in luminescence efficiency (light output) with sample temperature. In the present work, the UV radiofluorescence (RF) signals of three different quartz samples during cooling from 500 °C to room temperature were monitored and analysed. Resulting thermal quenching parameters 〈em〉W〈/em〉 (activation energy) and 〈em〉K〈/em〉 (constant) agree with published values, except for one sample. Another quenching process in quartz is the reduction of luminescence sensitivity following irradiation (dose quenching), mainly known for TL and OSL of old samples with large palaeodoses. Here, the intensity of the 110 °C TL peak and the OSL signal were used to monitor the dose quenching effect. UV-OSL and UV-TL signals are analysed and found to be very similar. The UV-RF recorded during irradiation in between repeated cycles of TL and OSL measurements differs at high doses from a continuously recorded reference signal.〈/p〉 〈p〉Furthermore, numerical simulations are presented to decipher the charge transport processes in quartz. In summary, thermal quenching simulations are capable of mimicking experimental findings and confirm that UV-RF is a valuable tool to determine thermal quenching parameters. Dose quenching simulations differ from experimental results in the high dose range but help to understand the basic principle of dose quenching: charge competition of different centres.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Sunil Thomas, M.L. Chithambo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report the thermoluminescence of Sm〈sup〉3+〈/sup〉-doped P〈sub〉2〈/sub〉O〈sub〉5〈/sub〉-K〈sub〉2〈/sub〉O-MgO-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-ZnF〈sub〉2〈/sub〉 glass. A glow-curve measured at 1 °C/s after beta irradiation to 10 Gy shows two peaks; a broad high intensity one at 214.0 ± 0.4 °C and a weaker intensity peak at 75.2 ± 0.8 °C. The dependence of peak position on partial heating as well as on irradiation suggest that the main peak at 214 °C is a combination of several overlapping peaks. The activation energy of the different components of the main peak, calculated using the initial-rise method, differ showing that the components are distinct. The reproducibility, fading and dose response were examined by considering the dominant component of the main peak. The intensity of the peak changes with heating rate in a manner consistent with thermal quenching.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Peter Rubovič, Daniela Ekendahl, Zdeněk Vykydal, Jiří Hůlka, Benedikt Bergmann, Stanislav Pospíšil, Ivan Štekl〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We used the hybrid semiconductor pixel detector Timepix as an area dosimeter in mixed neutron-gamma fields. The surface of the detector was covered with several converters based on 〈sup〉6〈/sup〉Li, polyethylene, Th and enriched U. We used three different neutron sources for calibration of the device – thermal neutrons from graphite pile, 〈sup〉241〈/sup〉Am-Be and 〈sup〉252〈/sup〉Cf. The desired neutron component of dosimetry and operational quantities can be determined by counting events under the converters. The segmentation of the Timepix detector and its capability to measure energy deposition of each interacting quantum of ionizing radiation allows a separation of neutron events from X-ray/gamma or electron interaction. Thus, the device can also be used for simultaneous X-ray and gamma dosimetry, where it is in some aspects superior to most of the commercial devices, given its detection threshold of 3–5 keV.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 August 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): M. Autzen, A.S. Murray, G. Guérin, L. Baly, C. Ankjærgaard, M. Bailey, M. Jain, J.-P. Buylaert〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We use both modelling and high dose experiments to investigate the effects of charge imbalance on luminescence. Charge entering and leaving irradiated 50 μm grains is modelled using Geant4 to predict the degree of charge imbalance a grain will experience when exposed to i) the 〈sup〉90〈/sup〉Sr/〈sup〉90〈/sup〉Y beta source of a Risø TL/OSL reader, ii) a 200 keV electron beam, and iii) the ‘infinite-matrix’ 〈sup〉40〈/sup〉K β spectrum. All simulations predict that between 1.4% and 2.9% more electrons enter a grain than leave, resulting in a net negative charge in the grain. The possible effects of this charge imbalance on luminescence production are discussed and experiments designed to test the resulting hypotheses; these involve giving very high doses (hundreds of kGy) to silt-sized quartz grains using low energy electrons (200 keV). Up to 700 kGy, we observe an increase in both luminescence output resulting from these high doses, and in sensitivity; above 700 kGy, both decrease. These observations, together with a slower luminescence decay during stimulation following higher doses, are consistent with the hypothesis of a decrease in hole population as a result of net accumulation of electrons during irradiation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 16 May 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): E.G. Yukihara, A.C. Coleman, R.H. Biswas, R. Lambert, F. Herman, G.E. King〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermoluminescence (TL) has traditionally been used to estimate the depth of trapping centers in luminescence materials and explain the isothermal decay in the case of synthetic dosimeters and natural materials used in luminescence dating. Nevertheless, new fields of application of TL and optically stimulated luminescence (OSL) materials, namely particle temperature sensing and thermochronometry, motivate a need for accurate models for the luminescence processes and estimation of the trapping parameters, in particular activation energy and frequency factor. Although calibration of the TL materials may be possible and recommended in some applications, using for example, microheaters, laser heating or pyroprobes, the procedures can be complicated and time consuming. With TL, however, appropriate models with parameters obtained in laboratory conditions can in principle be used to predict the temperature and time dependence of the stimulation processes in the microsecond to the second timescales (in the case of particle temperature sensing), and in the tens of thousands years (in the case of thermochronometry). In this paper we present the fundamentals of temperature sensing using TL, tracing parallels between the applications in thermochronometry and in particle temperature sensing, and review the main challenges, both fundamental and practical, for the advancement of the technique. Fundamental challenges are the very wide timescales involved in these applications, the need for better TL models, and the inherent time-temperature ambiguity in the Arrhenius equation, in addition to other practical problems. Possible solutions to these challenges and future research directions are discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 9 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): I.K. Bailiff, G. Adamiec, R. Chen, M. Chithambo, A. Chruścińska, G.A.T. Duller, M. Jain〈/p〉

Description: 〈p〉Publication date: Available online 4 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): J.-P. Buylaert, G. Újvári, A.S. Murray, R.K. Smedley, M. Kook〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Previous work has been unable to establish a relationship between K concentration and D〈sub〉e〈/sub〉 in single-grains of feldspar. Here we use four well-bleached sediments with low external dose rate (typically ≤1.5 Gy ka〈sup〉−1〈/sup〉) to investigate this relationship. Single and multi-grain pIRIR measurements and μ-XRF analyses are made on Na- and K-rich extracts; μ-XRF is directly applied to grains sitting in single-grain discs to minimise uncertainty in grain identification. Micro-XRF is shown to be sufficiently precise and accurate and luminescence instrument reproducibility is confirmed using dose recovery measurements on heated feldspar. We are again unable to establish any correlation between single-grain D〈sub〉e〈/sub〉 and K concentration, even in feldspar grains for which the internal dose rate should dominate. We also measure highly variable Rb concentrations in these grains and are unable to detect, at the single-grain level, the correlation between K and Rb previously observed in multi-grain investigations. Nevertheless, these results are unable to explain the lack of D〈sub〉e〈/sub〉 correlation with K. Finally, we investigate the dependence of D〈sub〉e〈/sub〉 on grain size (isochrons). Linear correlations are observed but slopes are inconsistent with model prediction. We conclude that this surprising absence of the expected relationships between dose and K concentration and grain size does not arise from analytical precision, incomplete bleaching, sediment mixing or fading. It appears that we cannot measure feldspar doses in these samples as accurately as we thought.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): R.R. Dawam, M.L. Chithambo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The thermoluminescence of synthetic quartz annealed at various temperatures up to 900 °C is reported. Glow curves measured at 1 〈sup〉o〈/sup〉Cs〈sup〉−1〈/sup〉 following beta irradiation to 40 Gy from a sample annealed at 500 °C and from an unannealed one consist of a prominent peak at 70 °C and secondary peaks at 110, 180 and 310 °C. In comparison, the glow peak from the sample annealed at 900 °C consists of three peaks but with the main peak at 86 °C and other lower intensity peaks at 170 and 310 °C. Kinetic analysis was carried out on the main peak only in each case. The order of kinetics of this peak was determined to be first order using various methods. The activation energy was evaluated as an average of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mn〉0.90〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mo〉±〈/mo〉〈mn〉0.02〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈/mrow〉〈/math〉eV for the unannealed sample and the one annealed at 500 °C. However, when the synthetic quartz is annealed at 900 °C, the activation energy decreases to 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.gif" overflow="scroll"〉〈mrow〉〈mn〉0.65〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mo〉±〈/mo〉〈mspace width="0.25em"〉〈/mspace〉〈mn〉0.02〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈/mrow〉〈/math〉eV. The main point of interest however concerns thermal quenching. It was noted that for the sample annealed at 500 °C as well as the unannealed one, the maximum intensity of the main peak decreases with heating rate. This phenomenon is associated with thermal quenching. When the same experiment is carried out using quartz annealed at 900 °C and irradiated to the same dose, namely 40 Gy, the intensity increases with heating rate. This would imply that this sample is not affected by thermal quenching. Using the notion that the radiative and non-radiative recombination routes are competitive, we repeated the experiment using a low dose of 3 Gy. In this case, the intensity decreased with heating rate showing that the process can be tuned. The activation energy for thermal quenching for the samples annealed at 900 °C, 500 °C and unnannealed one was found as 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.gif" overflow="scroll"〉〈mrow〉〈mn〉0.65〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mspace width="0.25em"〉〈/mspace〉〈mo〉±〈/mo〉〈mspace width="0.25em"〉〈/mspace〉〈mn〉0.02〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈/mrow〉〈/math〉eV, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.gif" overflow="scroll"〉〈mrow〉〈mn〉0.82〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mo〉±〈/mo〉〈mspace width="0.25em"〉〈/mspace〉〈mn〉0.02〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈/mrow〉〈/math〉eV and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.gif" overflow="scroll"〉〈mrow〉〈mn〉0.95〈/mn〉〈mo〉±〈/mo〉〈mspace width="0.25em"〉〈/mspace〉〈mn〉0.06〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈/mrow〉〈/math〉eV. Evidently, annealing affects recombination processes in synthetic quartz.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 February 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): A.J. Cresswell, J. Carter, D.C.W. Sanderson〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The dating of materials using stored dose methods requires accurate determination of the environmental dose rate. The calculation of dose rates from radionuclide concentrations requires conversion parameters derived from nuclear data (half life, decay energies and intensities, and branching ratios). With the substantial body of primary data, it is convenient to use data from evaluated libraries. These libraries show variations reflecting both newer data unavailable to earlier evaluations and the relative importance given to different data sets by the evaluators. Commonly used conversion parameters derive from the Evaluated Nuclear Structure Data File (ENSDF), either directly or from secondary publications, with new tabulations produced in recent years following revisions to this library. Other international evaluations of nuclear data include the NEA/OECD supported JEF2.2 and JEFF3.11 evaluations, and the Decay Data Evaluation Project (DDEP). A technique comparing different evaluations to identify data that can not be confidently used has been developed. These differences have been investigated with an evaluation of underlying nuclear data. Particular radionuclides of interest are discussed; 〈sup〉214〈/sup〉Bi where recent evaluations depend on a single high precision data set, 〈sup〉228〈/sup〉Ac where the decay scheme is incomplete and further measurements are required, and 〈sup〉40〈/sup〉K where the mean beta energy has been calculated in the evaluations using an incorrect shape factor. Revised dose rate conversion factors have been produced, which are largely consistent with earlier values with the exception of the 〈sup〉40〈/sup〉K beta parameter which is 4% higher than recent values but consistent with earlier calculations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): P. Palczewski, A. Chruścińska〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recently it was shown that making use of the dependency of optical cross-section (OCS) of trap on the experimental parameters can help to enhance the ability to separate signals from different traps. When the light source applied for stimulation delivers the spectral band of a finite width, the physical quantity that governs the luminescence process is not the OCS value but rather a kind of weighted average of the OCS value over the range of the stimulation band. Changes of the shape of the stimulation band allow to regulate the shape of OSL curve. The band shape modulation can be easily attained using at least two sources of light. The shape of a band that is the sum of bands from two sources can be controlled by changing the emission intensity of each source. The presented results of simulations and experiments demonstrate what can be achieved by means of such a band shape modulation. The ability to separate the signal from different kinds of traps depends significantly on the selection of the experimental parameters such as the energy of the maxima of the component spectral bands, the difference of these maxima as well as the rate and the character of light intensity changes. When the experimental parameters are properly selected the OSL curve for a single trap has the form of a peak.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 23 February 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Debra Colarossi, Melissa S. Chapot, Geoff A.T. Duller, Helen M. Roberts〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Basic assumptions of the single aliquot regenerative dose (SAR) protocol are tested using the violet stimulated luminescence (VSL) signal from quartz. The VSL signal is shown to be reduced to a sufficiently low background level between SAR steps, and the SAR protocol appears to adequately correct for sensitivity changes during measurement. The VSL SAR protocol can recover a large (405 Gy) laboratory beta dose within uncertainties, however the mean value for the dose recovery ratio is commonly 0.8 or less. This poor behaviour is echoed in the measurements of equivalent dose (D〈sub〉e〈/sub〉) for a sample with an expected D〈sub〉e〈/sub〉 of ∼354 Gy, which underestimates D〈sub〉e〈/sub〉 by 50–70%. Further investigations are required to understand the mechanisms underlying these underestimations in VSL SAR D〈sub〉e〈/sub〉 values.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): V. Altunal, Z. Yegingil, T. Tuken, T. Depci, A. Ozdemir, V. Guckan, N. Nur, K. Kurt, E. Bulur〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Optically Stimulated Luminescence (OSL) properties of the sol-gel synthesized nano-powders of Beryllium Oxide (BeO) were investigated. Luminescence properties of BeO nanoparticles are dependent on the crystal structure, particle size, and morphology and therefore strongly dependent on the way of synthesis, thus the preparation was modified to enhance the OSL signal from the material. Structural, thermal and morphological properties of BeO in nanopowder and pellet forms were studied using X-Ray Diffraction (XRD), Fourier Transform Infrared Microscopy (FTIR), Simultaneous Thermal Analysis STA (Thermo Gravimetric Analysis (TGA)/Differential Scanning Calorimetry (DSC)) and Scanning Electronic Microscopy (SEM) techniques. XRD and STA analysis suggested an enhancement in crystallinity and thermal stability of the BeO with increasing sintering temperature.〈/p〉 〈p〉OSL dosimetric properties of the pellets prepared by pressing the synthesized powders were investigated in detail. Thermal stability of the signal as determined with a pulse heating experiment has shown that the OSL signal was stable up to depleted at around 300 °C, suggesting the suitability for dosimetric purposes. Dose response of OSL signals was observed to be linear in the dose range 0.1–100 Gy. The minimum detectable dose limit was estimated at around 100 μGy. Replicated measurements of the samples irradiated with the same dose indicated a good repeatability. Fading properties of the OSL signals were also studied up to 1 month. OSL signals of BeO pellets were decreased by approximately 11% at the end of 7 days and by about 17% at the end of 30 days when compared with the first readout.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): X.J. Ou, H.M. Roberts, G.A.T. Duller, M.D. Gunn, W.T. Perkins〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉There is growing interest in rock surface burial and exposure luminescence dating for use in Quaternary science and in archaeology. Such methods have enormous potential both in increasing the range of sedimentary contexts that can be dated, and improving the accuracy and the precision of dating within those contexts. Bleaching of the luminescence signal with depth into the rock surface is likely to vary with lithology. However, previous work on rock surface dating has not systematically studied the differences in light attenuation for rocks of different lithologies, or directly quantified the attenuation of light in different rock surfaces. This study investigates the attenuation of light in different rock types (greywacke, sandstone, two granites and quartzite) using two different approaches: 1) sunlight bleaching experiments, to assess the residual infrared stimulated luminescence signal measured at 50 °C (IRSL〈sub〉50〈/sub〉) and the post-IR IRSL signal measured at 225 °C (post-IR IRSL〈sub〉225〈/sub〉) at different depths within the rocks after different durations of exposure to daylight; and, 2) direct measurement of light attenuation in rock slices using a spectrometer. Data from the spectrometer shows that for all rocks, attenuation is greater for shorter wavelengths (∼400 nm) than longer ones. A consistent difference in attenuation coefficient is seen when comparing the IRSL〈sub〉50〈/sub〉 and the post-IR IRSL〈sub〉225〈/sub〉 signals; this is thought to reflect the different sensitivity of these two signals to infrared and visible light. Direct measurement using a spectrometer is much more rapid than undertaking a bleaching experiment, and also provides wavelength-resolved attenuation data. Comparison of the numerical values from the two approaches is complex, but they yield consistent results. For the samples analysed here, the rocks that appear lightest in colour show the least attenuation of light and the luminescence signals are bleached to the greatest depths, and are thus the most suitable for dating using luminescence.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 21 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): R. Kumar, M. Kook, A.S. Murray, M. Jain〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Prasad et al. (2017) recently developed a new method of measuring the dosimetric signal in feldspar, based on a Stokes-shifted photoluminescence emission (excitation energy 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mo〉∼〈/mo〉〈/math〉1.40eV (885 nm), emission energy〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mo〉∼〈/mo〉〈/math〉1.30eV (955 nm)). The new signal, termed as infrared photoluminescence (IRPL), was shown to arise from radiative relaxation of the excited state of the principle trap (dosimetric trap), and allows non-destructive probing of the dosimetric information. Thus, IRPL provides a unique tool to study physical characteristics of these metastable states in feldspar, e.g., number density and spatial distribution, trap depth, photo-ionisation and capture cross-section, excited state lifetime, and tunneling probabilities. The IRPL emission is apparently related to the infrared radioluminescence (IR-RL) in K-feldspar (Trautmann et al., 1998); in the latter, however, the electrons relax after being trapped as a result of exposure to ionising radiation, rather than as a result of excitation within the trap.〈/p〉 〈p〉In this study, we report the discovery of a second IRPL emission centred at 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mo〉∼〈/mo〉〈/math〉1.41eV (880 nm) in a K-feldspar which arises in response to excitation with 1.49eV photons. Based on the temperature- and dose-dependent behaviour of IRPL and IR-RL, we conclude that the same defect(s) participates in these two emissions. However, IRPL emission is governed by the characteristics of the principle trap (defect) alone, whereas IR-RL depends additionally on thermally assisted transport within the band-tail states. Since IRPL is a site selective technique, it does not, unlike IR-RL, suffer from contamination from higher energy emissions (e.g. from 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.gif" overflow="scroll"〉〈mrow〉〈msup〉〈mrow〉〈mtext〉Fe〈/mtext〉〈/mrow〉〈mrow〉〈mn〉3〈/mn〉〈mo〉+〈/mo〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉). This lack of contamination, and the possibility for thermal/optical pre-treatments and repeated measurements of the same trapped electrons, suggest that IRPL is a robust alternative to IR-RL.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Z.M. Hu, X.Y. Peng, Z.J. Chen, T.F. Du, L.J. Ge, X. Yuan, Z.Q. Cui, W.J. Zhu, Z.M. Wang, X. Zhu, J.X. Chen, X.Q. Li, G.H. Zhang, J. Chen, H. Zhang, G. Gorini, T.S. Fan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A De Pangher-type long counter was constructed at Peking University for neutron fluence measurement. The responses and effective centers of the long counter were calculated using the Monte Carlo method. The variations with neutron energy of the position of the effective center, calculated by the Monte Carlo code, was experimentally validated with a 〈sup〉241〈/sup〉AmBe neutron source and several mono-energetic neutron sources ranging from 100 keV to 6 MeV. Long counter calibration was performed using a radionuclide source from Peking University, and neutron fluence measured by the calibrated long counter was successfully compared to values determined with reference instruments (two recoil proton counters and a 〈sup〉238〈/sup〉U fission chamber). The relative deviations were lower than 6% along the whole energy range. The calibrated long counter was thus successfully applied in the calibration of a Bonner sphere spectrometer.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 14 April 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Weili Bi, Chaolu Yi, Haijun Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Establishing the quantitative relation between electron spin resonance (ESR) signal intensity and quartz mass can help both to improve ESR signal measurement and to allow a greater understanding of the characteristics of ESR color centers. However, this relation has not as yet been clearly defined. We measured the ESR signal intensities in the Ge and E′ centers in the pure quartz in our samples. We applied both standard and additional doses of irradiation by using two different types of spectrometers across different timeframes in an attempt to establish the quantitative relation between the ESR signal intensities in Ge and E’ centers and quartz mass. The linear correlation established between ESR signal intensity and quartz mass was significant for the samples treated with additional irradiation, but there was, overall, no close correlation between ESR signal intensity and quartz mass for samples which were not given additional irradiation doses. A significant correlation between ESR signal intensity and quartz masses of weight ≥0.35 g was established for Ge center, but this was not the case for quartz masses of weight ≤0.3 g. This would suggest that the apparent instability of Ge center is likely aroused by the application of weak signals. The quantitative relation between ESR signal intensity and quartz mass might therefore provide a possible solution for the correction of signal intensities in aliquots of unequal weight in laboratory measurements, particularly for non-irradiated aliquots on the dose growth curve. We would propose that larger quartz masses be used for the clear identification of Ge center signal, for enhancing ESR signal intensity, and for improving the quality of signal measurement.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 August 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): I.K. Bailiff〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Previous work has demonstrated the feasibility of performing spatially resolved luminescence measurements with sliced solid materials (e.g., rock and ceramic) to determine the cumulative absorbed dose to individual luminescent grains 〈em〉in situ〈/em〉. In the present study, aspects of the dosimetry of individual grains that are truncated during slicing were examined using radiation transport simulations employing simplified geometries. The results of the simulations were applied to model the effect of grain truncation on the dosimetry of grains, in particular the beta attenuation factor and the laboratory beta source dose rate for whole and partial volumes of individual spherical grains. Where a material contains a wide range of coarse grain sizes there is the potential for misinterpreting the size of the parent grain on the basis of an examination of the shape and size of the truncated grain section exposed in the slice surface. If the original grain size is underestimated, which is likely, the simulations predict an overestimation of both the beta attenuation factor and the laboratory source beta dose rate, the maximum extent of which depends on the range of grain sizes present in the material. The simulations also indicate that by limiting the depth from the surface within which the average absorbed dose is determined, approximating the effects of opacity of the mineral, the magnitude of these deviations is reduced. However, a consequence of particular interest deriving from these results is that, when evaluating the age equation, the changes in the two quantities compensate, acting to moderate the overall effect on the calculated age for an individual grain, depending on the geometry of the grain and the composition of the sample material.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Julie A. Durcan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Signal stability is a key consideration when using luminescence dating techniques. The stability, or lifetime, of a signal is one of the factors determining the upper age constraint for luminescence dating, and it has been suggested that the signal being used for dating should have a lifetime at least ten times the age being dated in order to limit age underestimation to an upper loss of 5%. Accurate derivations of signal stability and associated kinetic parameters, such as trap depth and frequency factor, are also important parameters for constraining rock cooling histories in thermochronometric techniques. This paper aims to assess the reproducibility of lifetime determinations derived using isothermal decay measurements. Variability arising from changing the isothermal decay protocol used is tested. Simulating Arrhenius plot from fixed trap depth and frequency values shows that whilst trap depth can be relatively well constrained, significant variability in the frequency factor, hence signal lifetime, should be expected. This paper also uses luminescence signals measured using different wavelengths to better understand the impact of signal from non-fast quartz OSL components in lifetime calculations. The presence of contributions from non-fast OSL components in the initial part of the OSL signal can result in the lifetime being calculated from charge contributions from multiple traps, not solely the 325 °C TL peak, as has been previously assumed. This effect can be reduced however by stimulating luminescence signals with longer wavelengths to better isolate signal from the fast component.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Elizabeth L. Chamberlain, Jakob Wallinga, Zhixiong Shen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Optically stimulated luminescence (OSL) dating of heterogeneously-bleached sediment by means of a minimum age model requires the input of a 'sigma_b' (〈em〉σ〈/em〉〈sub〉〈em〉b〈/em〉〈/sub〉) value describing the overdispersion of the single-aliquot 〈em〉D〈/em〉〈sub〉〈em〉e〈/em〉〈/sub〉 distribution expected for a well-bleached sample. We propose that 〈em〉σ〈/em〉〈sub〉〈em〉b〈/em〉〈/sub〉 and associated uncertainty can be accurately determined if a large dataset of 〈em〉D〈/em〉〈sub〉〈em〉e〈/em〉〈/sub〉 distributions is available and includes well-bleached samples. Our approach applies the bootstrapped Minimum Age Model (bootMAM) to a dataset of overdispersions in 〈em〉D〈/em〉〈sub〉〈em〉e〈/em〉〈/sub〉 distributions, to obtain quantitative estimates of 〈em〉σ〈/em〉〈sub〉〈em〉b〈/em〉〈/sub〉. Corrections are made for constant-diameter aliquots of different grain sizes, based on the published dependency of overdispersion on the number of grains per aliquot. These adapted 〈em〉σ〈/em〉〈sub〉〈em〉b〈/em〉〈/sub〉 values are then input to bootMAM to obtain robust paleodoses for the samples. We test the sensitivity of paleodose to 〈em〉σ〈/em〉〈sub〉〈em〉b〈/em〉〈/sub〉 and we demonstrate that with correct 〈em〉σ〈/em〉〈sub〉〈em〉b〈/em〉〈/sub〉, identical paleodoses are obtained using bootMAM and the Central Age Model on samples judged to be well-bleached. We conclude that for large datasets consisting of well- and heterogeneously-bleached samples, appropriate 〈em〉σ〈/em〉〈sub〉〈em〉b〈/em〉〈/sub〉 values can be obtained from the data, and that bootMAM can be applied to all samples within this dataset.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 14 April 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): Alastair C. Cunningham, Andrew S. Murray, Simon J. Armitage, Martin Autzen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The beta-particle emission from a sediment or rock sample can be measured very precisely using beta-counting instruments. The observed count rate is largely a function of the radionuclide concentration in the sample, so has the potential to provide a precise estimate of the natural radiation dose rate. However, the count rate is also sensitive to the attenuation of beta particles in the sample, and the relative proportions of the different radionuclide sources. Here we devise a correction for the self-attenuation effect using dilution analysis, and show that imprecise prior knowledge of radionuclide activity is sufficient for calculation of an accurate combined beta-plus-gamma dry dose rate. The method is tested on a selection of archive samples, and compared with results from high-resolution gamma-spectrometry. We show that with counting uncertainty ∼2%, and calibration uncertainty ∼2%, the total random uncertainty of the beta-plus-gamma dry dose rate is less than 3%. For most natural sediments, this level of precision equal to, or better than, that obtainable with other methods.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): Z. Kowalski, S.M. Kaczmarek, W. Drozdowski, M.E. Witkowski, M. Makowski, K. Brylew, M. Berkowski, M. Głowacki〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, radioluminescence, low temperature thermoluminescence, and light yield of ZnWO〈sub〉4〈/sub〉, ZnWO〈sub〉4〈/sub〉:Ca, and ZnWO〈sub〉4〈/sub〉:Ca, Eu single crystals is reported. It is shown that although the single doping with Ca improves, in a limited scope, the scintillation properties of the studied material, it is not the case with the double doping with Ca and Eu. The values of light yield and energy resolution of the investigated ZnWO〈sub〉4〈/sub〉:Ca, Eu samples are clearly worse compared to either ZnWO〈sub〉4〈/sub〉 or ZnWO〈sub〉4〈/sub〉:Ca. The X-ray excited spectra of all the crystals, dominated by the intrinsic luminescence, unveil a strong decrease of intensity from 10 to 350 K; the addition of Eu does not improve this property. Furthermore, the presence of Eu strongly influences the low temperature glow curves, i. a. by introducing a distinct peak close to 150 K.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 119〈/p〉 〈p〉Author(s): Daniela Ekendahl, Peter Rubovič, Ivan Hupka, Libor Judas, Pavel Žlebčík〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A historical radium (〈sup〉226〈/sup〉Ra) needle was found in a building in Prague. The needle was concealed in a wall under a window frame. Ambient dose equivalent rate measured in close proximity to the frame reached up to 2 mSv/h. The place was located between a corridor and a staircase where people normally did not stay; hence, any significant radiation exposure was not suspected. Because of a remarkable history of the building, our speculation was that the needle could have been concealed there during World War II. To verify this assumption, one adjacent brick nearest to the place of the find was removed. The brick was used for retrospective dosimetry based on optically stimulated luminescence (OSL) of quartz extracted from a chosen brick block. Dose rate values inside the brick block were determined by a laboratory reconstruction. The original exposure conditions were simulated using the needle and a brick wall containing thermoluminescence detectors (TLDs). We also performed a computational simulation with the Monte Carlo technique. The simulation provided us a more detailed dose rate distribution inside the brick block. Finally, we compared OSL quartz, TLD, and Monte Carlo results. A good agreement among the results supports the speculation that the radium needle was concealed during World War II.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements, Volume 118〈/p〉 〈p〉Author(s): Dobromir Pressyanov, Dimitar Dimitrov, Ivelina Dimitrova〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The recent European directive 59/2013 set reference levels for radon at working places. Since usually the personnel spend only part of the day (e. g. 8 h) at work, it is useful to have passive radon monitors that are sensitive only within a certain time window (e. g. the working hours). This work proposes a conceptual design of such a monitor and tests the feasibility of the approach. The design is based on a solid state nuclear track detector (SSNTD) that rotates over a radon absorber during the monitored period of the day. The SSNTD (Kodak Pathe LR-115 type II) has an energy window that makes it insensitive to 〈sup〉222〈/sup〉Rn and 〈sup〉220〈/sup〉Rn progeny plated-out on the surfaces. It only registers alpha particles of the absorbed 〈sup〉222〈/sup〉Rn and its short-lived progeny 〈sup〉218〈/sup〉Po, which is achieved by optimization of the absorber thickness. The absorber construction is further optimized to decrease the inertia of the signal. The modeling and the pilot experimental results show that with a composite absorber consisting of a stack of Makrofol N foils with thickness of less than 7 μm each, the inertia of the signal is less than 20 min. The estimated minimum detectable activity concentration (MDAC) for the proposed 〈sup〉222〈/sup〉Rn monitor is about 15 Bq m〈sup〉−3〈/sup〉 for year-long working time exposure (2000 h/year) or 60 Bq m〈sup〉−3〈/sup〉 for 3- month exposure period (500 h).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): M.L. Chithambo, J.M. Kalita〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report the dosimetric features of ultra-high molecular weight polyethylene (UHMWPE) using luminescence optically stimulated using 470 nm blue light. Samples irradiated to between 1 and 1000 Gy produces luminescence that increases with irradiation dose to produce a linear dose response between 1 and 1000 Gy. The sample was determined not to be affected by pre-dose in tests using a pre-dose of 4000 Gy. This characteristic precludes the need for elaborate background erasing routines typical of dosimetry experiments. The signal has good reproducibility. We used this property to test recovery of ‘unknown’ doses with encouraging results. It was observed that luminescence can also be stimulated using 870 nm infrared light. The dose response, fading, pre-dose effect and the ability to optically stimulate luminescence from the polymer is discussed in terms of curing involving free-radicals.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Radiation Measurements〈/p〉 〈p〉Author(s): M. Kook, R. Kumar, A.S. Murray, K.J. Thomsen, M. Jain〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A facility for the measurement of infrared photoluminescence (IRPL) has been developed for the Risø TL/OSL reader. The new IRPL measurement system uses an external laser light source at 1.49 eV (830 nm) and two photomultiplier tubes (PMT) for detecting emissions at ∼1.41 eV (880 nm) and ∼1.3 eV (955 nm) and an EMCCD. Pulsed IRPL measurement ensures a low background count rate by allowing the rejection of breakthrough from excitation light. We present the results of integrated IRPL measurements on both multiple- and single-grain aliquots, and finally demonstrate the potential of imaging natural K-feldspar samples and a granite rock slice.〈/p〉〈/div〉 〈/div〉