Radiation Measurements最新文献

This work aimed to investigate and compare the luminescence properties of CaSO₄:Tb, CaSO₄:Mn, and CaSO₄:Mn,Tb synthesized by slow evaporation route. The crystalline structure, morphology, and optical properties of the phosphors were characterized by X-ray diffraction analysis (XRD), photoluminescence (PL), radioluminescence (RL), and scanning electron microscopy (SEM). In addition, thermoluminescence (TL) and optically stimulated luminescence (OSL) were used to comprehensively investigate the dosimetric properties of the phosphors, such as the TL glow curve and continuous wave OSL (CW-OSL) curves, dose-response and its reproducibility, fading, and sensitivity. For dosimetric analyses, the samples were irradiated with beta radiation. PL and RL emission spectra confirmed the presence of Tb³⁺ and Mn²⁺ ions in crystalline matrices. The samples showed a typical exponential OSL decay curve, indicating that the charge traps have a high photoionization cross-section for blue LEDs. The synthesized pellets exhibited good luminescent and dosimetric properties, with linear luminescent response over a wide dose range (169 mGy–100 Gy) and reproducibility of both OSL and TL signals. Furthermore, the incorporation of terbium as a co-dopant in the CaSO₄:Mn matrix reduced its fading from 75% to only 17%. The phosphors had high TL and OSL sensitivities in comparison to some commercially available dosimeters.

One of the basic parameters in the use of thermoluminescent detectors is the angular characteristics, i.e. receiving different signals depending on the angle of radiation exposure. The TLD detector is typically installed in a slide/badge and here the angular characteristics may have an influence, adding non-uniform coverage of the detectors with filters for the correct determination of the dose as a function of energy, because the energy characteristics are usually not flat.

As part of the work, special MCP-N (LiF:Mg, Cu, P) detectors of various shapes were prepared to improve the angular characteristics. The detectors were round pellets with the same circular shape with a diameter of 4.5 mm, and a modified form inside (large and small drilled holes) or a modified surface (cavity or hemisphere). For comparison, standard MCP-N type detectors were used. Detectors in special boxes were exposed to X-rays with an energy of 80 keV. The radiation beam was formed by a medical X-ray apparatus adapted for experiments at the Warsaw University of Technology in Warsaw. Exposures were made for angles of 0, 30, 45, 50, and 90° for a dose of 1.5 mGy.

Results show that it is possible to improve the angular characteristics for detectors with modified shapes. Better angular characteristics will allow for more accurate measurements, in particular in comparison tests, for accreditation and other calibrations. Especially improved angular dependence detectors could be useful for H*(10) environmental measurements.

To address the issue of decreased measurement accuracy in radon measurement devices due to the effects of temperature and humidity, a method has been proposed for correcting radon measurement readings based on a FASTLOF (Fast Local Outlier Factor) and NPSO-BP (Normalized Particle Swarm Optimization-Back Propagation) neural network model. The study employed the RAD7 portable radon detector and utilized the FASTLOF, NPSO, and BP neural network algorithms to perform data detection and correlation analysis on the environmental temperature, humidity and instrument readings. A correction model for the measurement data was established and trained to enhance the validity of the instrument's readings. Validation and analysis were conducted using data sets, stable radon concentration measurements in HD-6 multifunctional self-controlled radon chamber, and indoor radon measurement experiments. The experimental results indicate that the model can effectively correct radon concentrations, improve the accuracy and stability of the measurement data, with the maximum relative error not exceeding 8.6%, thus meeting monitoring requirements.

The use of luminescence signals from single mineral grains for optical dating has become a valuable and frequently utilised tool in Quaternary Geochronology. Single grain luminescence dating is particularly beneficial in complex depositional settings, however the ability to measure single grain signals also offers the opportunity to assess intrinsic luminescence properties of individual mineral grains. The use of spatially resolved luminescence technologies such as an electron multiplier charge coupled device is of benefit when making luminescence measurements at single grain scales because they allow stimulation with light emitting diodes, and this offers a number of key benefits related to stimulation power when it comes to the assessment of characteristics such as optically stimulated luminescence (OSL) decay rate and the calculation of parameters such as the fast ratio and photo ionisation cross-sections. In this paper, the intra- and inter-sample variability of sensitised single grain thermoluminescence (TL) and OSL signals is considered. A comparison between TL and OSL signals is undertaken, as well as calculation of the fast ratio, OSL component photo ionisation cross-sections, thermal stability, and characteristic dose for a suite of quartz samples from a range of geographic locations and depositional settings. For these heated signals, key findings include the lack of relationship between OSL signal intensity and dominance of the fast component, the fitting of two components (a fast and slow component) is the most common fit for single grain OSL signals, characteristic doses from fast dominated signals suggesting saturation at c. 150 Gy, and the identification of the ultrafast OSL component. Intra-sample variability across all measured parameters is observed, suggesting that for this suite of samples, variability is the norm rather than the exception, and that the intrinsic luminescence characteristics of quartz are variable and diverse.

This paper presents a versatile and cost-effective system for the monitoring of X-ray exposure during dental cone beam computed tomography procedures based on silicon PIN photodiode detectors. The system, developed and implemented at the University of Pisa's School of Engineering, underwent characterization under a range of operational conditions focusing on full field-of-view 3D protocols used in adult patient examinations. This study was facilitated by the Azienda Ospedaliero Universitaria Pisana, which provided access to a Planmeca ProMax 3D Classic scanner for the research. During the investigation, photodiodes were placed both on the surface and inside an Alderson RANDO phantom head to assess the dose delivered to regions near radiation-sensitive areas such as the salivary glands, thyroid, eye lens, and laryngopharynx. The evaluation process spanned a spectrum of tube voltages, ranging from 60 to 90 kVp, and tube currents, extending up to 16 mA, to ensure a broad and thorough analysis. Furthermore, to reinforce the effectiveness of the silicon photodiodes' measurement capabilities, calibrated GR-200 A-type thermoluminescent dosimeters were positioned within the phantom head inserts to serve as a reference point. Complementing this setup, PCXMC Rotation 2.0 simulations were conducted to further the efficacy of the monitoring system, particularly tailored to the specific dental CBCT protocols being investigated. In conclusion, while the research revealed a generally consistent correlation across PCXMC simulations, photodiode readings, and thermoluminescent dosimeter measurements, it is important to note that a direct comparison was not exactly possible due to limitations in the size and positioning of the systems. Variations up to 20–35% were observed, primarily due to the different positioning of the dosimeters and the unique physical and operational traits of the different measurement methods employed. Nevertheless, the development of an affordable, easily deployable, and scalable dosimetry monitoring system may provide a substantial contribution to enhancing patient safety in dental radiology and aid in the optimization of diagnostic X-ray protocols.

This review explores current experimental methods for determining the radiation quality in ion beams. In this context, radiation quality is commonly evaluated using the averaged linear energy transfer (LET), a metric employed to assess the response of both biological and physical systems. Dose and averaged LET can be experimentally determined with passive detectors through various techniques that have seen recent improvements. Another metric related to the LET is the mean lineal energy, which is measurable using microdosimetric detectors. This review focuses on the available possibilities for evaluating the radiation quality using three microdosimeters (mini-TEPC, Silicon Telescope, and SOI Microplus), three passive luminescence detectors (based on optical, thermo-, and radiophoto-luminescence), three track-based detectors (track-etched detector, Timepix, fluorescent nuclear track detector), and a chemical detector based on alanine. A comparison of detector properties is provided along with an overview of the underlying mechanisms enabling LET assessment or measurements of the mean lineal energy with each detector type. Finally, this review summarizes the current possibilities of LET determination with respect to the needs for quality assurance in particle therapy. Areas for future research and development are suggested.

Accurate real-time monitoring of neutron beams and distinguishing between thermal, epithermal and fast neutron components in the presence of a photon background is crucial for the effectiveness of accelerator-based boron neutron capture therapy (AB-BNCT). In this work, we propose an innovative quadruple metal–oxide–semiconductor field-effect transistor (MOSFET) device for real-time, cost-effective beam quality control; one detector is kept uncovered while the other three are covered with either a B${}_4$C, cadmium and B${}_4$C or polyethylene converter.

Individual MOSFET converter configurations were optimised via Monte Carlo simulations to maximise signal selectivity across neutron energy spectra. Results demonstrate the quad-MOSFET device’s efficacy in quantifying changes in neutron flux, underscoring its potential as a useful instrument in the AB-BNCT quality control process.

The challenge of saturation at the high dose rate employed in FLASH radiotherapy and the lack of real-time 2D and 3D dosimeters create an opportunity for the use of plastic scintillators. This study presents the development of an online dosimetric system designed for electron FLASH radiotherapy applications: an array of dosimeters, made by plastic scintillating fibers, each one coupled to an optical fiber, was evaluated as a proof-of-concept using a LINAC providing 9 MeV electrons, at the Centro Pisano Flash Radiotherapy. Signal linearity was established up to 10 Gy/pulse, with a pulse duration of $4\mu s$. We also measured the signal variation across the beam profile using different applicators (30 mm, 50 mm and 100 mm in diameters) and we developed a geometrical model that accounts for the different amount of dose absorbed by the plastic scintillating fibers and the optical fibers. By fitting this model to the data, we estimated both the inter-calibration factors of the dosimeters, as well as the intrinsic ratio (i.e. for equal irradiated volumes) of spurious light in the optical fiber respect to the scintillation, which is equal to (4.7$\pm 0.1_{stat.}\pm 1.0_{syst.}$) %.

A high-performance oxygen terminated synthetic single crystal diamond (SCD) detector (4.5 × 4.5 × 0.5 mm³) is presented. The SCD detector exhibits an extremely low leakage current value of 0.29 pA/mm² with an electric field of 0.3 V/μm. The charge collection spectrum measured with a²³⁸Pu source (5.48 MeV α-particles) irradiation shows that the electron and hole charge collection efficiency (CCE) reach as high as 99.1% and 98.9%, with an energy resolution as low as 2.87% and 2.53%, respectively, compared to Si detector. The SCD detector shows excellent radiation hardness and stability under ⁶⁰Co γ-ray irradiation with a dose rate of 12.737 kGy/h at 150 V bias and is able to withstand a cumulative dose of up to at least 9.3 kGy. The detector output in current mode is linearly related to the dynamic dose rate (0.409 Gy/h-12.737 kGy/h). Similarly, the counting rate of the detector in counting mode exhibits a strong linear variation within the range of 2.6 mGy/h-1269.36 Gy/h. Our results fully indicate that our fabricated SCD detector can be potentially applied to harsh γ irradiation scenarios, which is of guiding significance on real-time dose monitoring.

The paper presents results of on-ground (pre-flight) calibrations and flight tests (cross-calibration and in situ measurements) of the new, Modified PILLE-ISS Dosimeters with reduced shielding, developed for the radiation monitoring of astronauts during their extravehicular activity (EVA) on board the International Space Station (ISS). The smaller dimensions and weight of the modified thermoluminescent dosimeter allows ergonomic and safe use during EVA, when the dosimeter kit is worn in the outer pocket of a spacesuit. The special design of the detector housing makes it possible to estimate the dose to the astronaut's skin during EVA more accurately. Both pre-flight calibration with high-energy protons and on-board cross-calibration at ISS showed that the variability of the relative sensitivities does not exceed (5–10)% for any of the Modified PILLE-ISS Dosimeters. The additional dose received by astronauts during ISS EVAs in 2023 was in the range (0.37–0.75) mGy (in water) based on the measurements. The corresponding dose rate outside ISS is consistent with the previous readings of other dosimetric equipment installed on the outer surface of space station.