Development of Ce³⁺ and Li⁺ co-doped magnesium borate glass ceramics for optically stimulated luminescence dosimetry

Magnesium tetraborate, MgB₄O₇, is an attractive host material for dosimetry due to the two characteristics: its low effective atomic number (Zeff = 8.4) and high neutron capture cross-section of the ¹⁰B isotope. Particularly, Ce³⁺ and Li⁺ ions co-doped MgB₄O₇ has shown optically stimulated luminescence (OSL) signal comparable to that of Al₂O₃:C, which is a well-known OSL dosimetry material. In this work, for further improvement of the dosimetric properties, a new synthesis route for MgB₄O₇:Ce³⁺-Li⁺ is described: glass-ceramic (GC) MgB₄O₇: Ce³⁺- Li⁺ samples were prepared by heat treatment of the magnesium borate glass with the composition, 25MgO–72B₂O₃–3Li₂O-0.3Ce³⁺. The prepared GC samples show UV-blue radioluminescence assigned to the Ce³⁺ 5d → 4f transition under X-ray irradiation and two thermoluminescence (TL) glow peaks related to the shallow and deep electron traps. Although fading of the TL and OSL signal was observed due to electron release from the shallow traps, the electrons captured by deep traps were stable at room temperature. Particularly, GC samples annealed at 750 °C and 800 °C, named GC750 and GC800, showed stable OSL up to 10 h following β-ray irradiation, after an initial fading mainly due to the presence of shallow traps in the material. From the viewpoint of this fading ratio, GC750 and GC800 showed potential as a practical OSL dosimeter

Increased dose efficiency of breast CT with grating interferometry

Refraction-based x-ray imaging can overcome the fundamental contrast limit of computed tomography (CT), particularly in soft tissue, but so far has been constrained to high-dose ex vivo applications or required highly coherent x-ray sources, such as synchrotrons. Here we demonstrate that grating interferometry (GI) is more dose efficient than conventional CT in imaging of human breast under close-to-clinical conditions. Our system, based on a conventional source and commercial gratings, outperformed conventional CT for spatial resolutions better than 263 µm and absorbed dose of 16 mGy. The sensitivity of GI is constrained by grating fabrication, and further progress will lead to significant improvements of clinical CT

Optically Stimulated Luminescence: Fundamentals and Applications

The book discusses advanced modern applications of optically stimulated luminescence including the appropriate fundamentals of the process. It features major chapters on the use of OSL in space radiation dosimetry, medical physics, personnel dosimetry, security, solid-state physics and other related applications. In each case, the underlying theory is discussed on an as-needed basis for a complete understanding of the phenomena, but with an emphasis of the practical applications of the technique. After an introductory chapter, Chapters 2 to 6 cover basic theory and practical aspects, persona

Experimental and Simulated Spectral Gamma-Ray Response of a NaI(Tl) Scintillation Detector used in Airborne Gamma-Ray Spectrometry

The objective of this work is to simulate the spectral gamma-ray response of NaI(Tl) scintillation detectors for airborne gamma-ray spectrometry (AGRS) using the state-of-the-art multi-purpose Monte Carlo code FLUKA. The study is based on a commercial airborne gamma-ray spectrometry detector system with four individual NaI(Tl) scintillation crystals and a total volume of 16.8 L. To validate the developed model, radiation measurements were conducted using 57Co, 60Co, 88Y, 109Cd, 133Ba, 137Cs and 152Eu calibration point sources with known activities and source-detector geometries under laboratory conditions. In addition, empirical calibration and resolution functions were derived from these measurements combined with additional radiation measurements adopting natural uranium, thorium and potassium volume sources. The simulation results show superior accuracy and precision compared to previous AGRS simulation models with a median relative spectral error < 10 % for most of the radiation sources. Moreover, the implementation of a lower level discriminator model and detailed modelling of the laboratory result in a significant improvement in model accuracy for spectral energies < 100 keV compared to previous studies. Yet thorough statistical analysis incorporating statistical and systematic uncertainty estimates revealed statistically significant deviations between the simulated and measured spectra in the spectral region around the Compton edge, which could be attributed to the scintillator non-proportionality. These findings imply that the linear energy deposition model applied in this and previously developed AGRS simulation models should be revised and considered to be replaced by more accurate non-proportional models.ISSN:1680-7340ISSN:1680-735

Investigation of TL and OSL detectors in ultra-high dose rate electron beams

Objective.This work aims at investigating the response of various thermally stimulated luminescence detectors (TLDs) and optically stimulated luminescence detectors (OSLDs) for dosimetry of ultra-high dose rate electron beams. The study was driven by the challenges of dosimetry at ultra-high dose rates and the importance of dosimetry for FLASH radiotherapy and radiobiology experiments.Approach.Three types of TLDs (LiF:Mg,Ti; LiF:Mg,Cu,P; CaF2:Tm) and one type of OSLD (Al2O3:C) were irradiated in a 15 MeV electron beam with instantaneous dose rates in the (1-324) kGy s-1range. Reference dosimetry was carried out with an integrating current transformer, which was calibrated in absorbed dose to water against a reference ionization chamber. Additionally, dose rate independent BeO OSLDs were employed as a reference. Beam non-uniformity was addressed using a matrix of TLDs/OSLDs.Main results.The investigated TLDs were shown to be dose rate independent within the experimental uncertainties, which take into account the uncertainty of the dosimetry protocol and the irradiation uncertainty. The relative deviation between the TLDs and the reference dose was lower than 4 % for all dose rates. A decreasing response with the dose rate was observed for Al2O3:C OSLDs, but still within 10 % from the reference dose.Significance.The precision of the investigated luminescence detectors make them suitable for dosimetry of ultra-high dose rate electron beams. Specifically, the dose rate independence of the TLDs can support the investigation of the beam uniformity as a function of the dose rate, which is one of the challenges of the employed beam. Al2O3:C OSLDs provided high precision measurements, but the decreasing response with the dose rate needs to be confirmed by additional experiments.ISSN:1361-6560ISSN:0031-915

The EURADOS CR-39 Quality task for the optimisation and harmonisation of personal neutron dosimetry with CR-39 (PADC)

CR-39 (PADC) nuclear track detectors are among the most widespread devices used for personal neutron dosimetry; however, some issues related to the variable material quality of the CR-39 polymer hinder the performance of CR-39-based dosemeters. For this reason, the Working Group 2 (WG2) of the European Radiation Dosimetry Group (EURADOS) has recently launched the CR-39 Quality task, a project aimed at improving and harmonising personal neutron dosimetry with CR-39 in Europe. Whitin this task, a close collaboration among researchers, individual monitoring services and dosemeter grade CR-39 manufacturers is achieved, thus facilitating the direct dialog between producer and consumer to reach an optimised material for personal neutron dosimetry applications

Editorial for the Radiation Measurements/Physics Open Virtual Special Issue Radiation dosimetry: current challenges and future directions

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.RST/Fundamental Aspects of Materials and Energ

The quest for new thermoluminescence and optically stimulated luminescence materials: Needs, strategies and pitfalls

The quest for new materials for thermoluminescence (TL) and optically stimulated luminescence (OSL) dosimetry continues to be a central line of research in luminescence dosimetry, occupying many groups and investigators, and is the topic of many publications. Nevertheless, it has also been a research area with many pitfalls, slow advances in our understanding of the luminescence processes, and rare improvements over existing materials. Therefore, this paper reviews the status of the field with the goal of addressing some fundamental questions: Is there a need for new luminescence materials for TL/OSL dosimetry? Can these materials be designed and, if so, are there strategies or rules that can be followed? What are the common pitfalls and how can they be avoided? By discussing these questions, we hope to contribute to a more guided approach to the development of new luminescent materials for dosimetry applications.RST/Fundamental Aspects of Materials and Energ

Characterization of LiF:Mg,Ti thermoluminescence detectors in low-LET proton beams at ultra-high dose rates

Objective. This work aims at characterizing LiF:Mg,Ti thermoluminescence detectors (TLDs) for dosimetry of a 250 MeV proton beam delivered at ultra-high dose rates (UHDR). Possible dose rate effects in LiF:Mg,Ti, as well as its usability for dosimetry of narrow proton beams are investigated. Approach. LiF:Mg,Ti (TLD-100TM Microcubes, 1 mm × 1 mm × 1 mm) was packaged in matrices of 5 × 5 detectors. The center of each matrix was irradiated with single-spot low-LET (energy >244 MeV) proton beam in the (1–4500) Gy s−1 average dose rates range. A beam reconstruction procedure was applied to the detectors irradiated at the highest dose rate (Gaussian beam sigma <2 mm) to correct for volumetric averaging effects. Reference dosimetry was carried out with a diamond detector and radiochromic films. The delivered number of protons was measured by a Faraday cup, which was employed to normalize the detector responses. Main results. The lateral beam spread obtained from the beam reconstruction agreed with the one derived from the radiochromic film measurements. No dose rates effects were observed in LiF:Mg,Ti for the investigated dose rates within 3% (k = 1). On average, the dose response of the TLDs agreed with the reference detectors within their uncertainties. The largest deviation (−5%) was measured at 4500 Gy s−1. Significance. The dose rate independence of LiF:Mg,Ti TLDs makes them suitable for dosimetry of UHDR proton beams. Additionally, the combination of a matrix of TLDs and the beam reconstruction can be applied to determine the beam profile of narrow proton beams.ISSN:1361-6560ISSN:0031-915