Radiation Measurements最新文献

The hybrid K-edge/X-ray fluorescence densitometer (HKED) is a combination of K-edge absorption technology (KED) and characteristic X-ray fluorescence (XRF), which has the advantages of direct, fast and non-destructive determination, and is an ideal non-destructive measurement technology for uranium and plutonium concentrations. In this paper, a new HKED was developed, primarily utilizing an X-ray tube from COMET, alongside high-purity germanium (HPGe) and cadmium telluride (CdTe) detectors from AMETEK ORTEC. This manuscript delves into several variables that influence measurement outcomes under predefined experimental conditions and operational prerequisites to pinpoint critical parameters. It was discerned that the adoption of a 160 kV high voltage setting markedly diminishes experimental interferences, while the beam current, optimally set at 2 mA, not only ensures a linear correlation with the count rate but also maximizes the effective count detected. The incorporation of a 2 cm fixed-length iron rod along the trajectory between the sample and the detector, complemented by an additional 3 mm external absorber before the KED detector, effectively mitigates direct X-ray exposure, thereby enhancing transmittance values to attainable extents. Subsequent to the determination of these pivotal parameters, validation of the HKED system's efficacy was conducted via performance evaluation tests on a laboratory-scale HKED setup. Measurements undertaken for both KED and XRF across an interval ranging from 300 to 3000 s fell within the 2σ boundary, affirming the system's stability. Repeated measurements of 50 g/L and 150 g/L uranium solutions yielded KED precision rates of 0.56% and 0.19%, respectively. Moreover, linear regression analyses linking transmittance, characteristic X-ray fluorescence, and uranium concentrations across a spectrum of 0–150 g/L underscored the laboratory HKED instrument's robust analytical capabilities. Notably, the relative discrepancy between theoretical predictions and empirical findings for the 150 g/L uranium sample was minimized to a commendable 0.58%.

Radiation damages to genes and cells occur at the DNA level, and therefore they are directly related to the spatial distribution of events caused by radiation at nanometer scale. Nanodosimetry introduces new quantities to correlate the initial features of radiation interactions and the likelihood of late radiobiological effects by means of Monte Carlo codes and, experimentally, with gas-detectors operating at low pressure.

Within this context, the aim of this work is to develop a numerical approach based on the implementation of different simulation tools to accurately describe the low energy electron transport processes within nanodosimetric devices. This approach was directly applied to perform a proof-of-concept study of the response of the electron collector of the STARTRACK nanodosimeter. Garfield++ was used to simulate the primary track structure of 5.8 MeV He-4 particles, while COMSOL Multiphysics was used to model the geometry and the electrostatic field of the electron collector. Available experimental data, measured with the STARTRACK nanodosimeter, were used to validate Garfield++ nanodosimetric spectrum before proceeding with the simulation of the electron transport stage in the drift volume, again performed with Garfield++. In order to verify the performance and reliability of the implemented codes, the nanodosimetric distributions were studied with the threefold objective of characterizing the time, space, and energy distributions of particles collected at the end of the drift volume. These results can offer a valuable insight into the overall working principle of nanodosimeters: this understanding can be pivotal in optimizing and refining the design of such devices, ultimately extending their effectiveness in particle track characterization during radiation therapy.

In this work, a novel sensitive composition of Fricke radio-chromic gel dosimeter based on polyvinyl alcohol (PVA), xylenol orange (XO), and physical cross-linking agent gellan gum (GG) is presented and evaluated with two optically detection methods. The Fricke dosimeter was irradiated up to 30Gy using medical linear accelerator and analyzed optically using ultraviolet visible (UV–Vis) spectrophotometry technique at wavelengths of 585 nm (i.e., within the visible range) and two-dimensional optical imaging system of charge-coupled-device (CCD) camera with a uniform red light-emitting-diode (LED) array source. The Fricke dosimeter demonstrated important properties including independence of beam energy and dose rate over the range studied. In addition, these dosimeters have high sensitivity in the range of 0–10Gy, and significant low diffusion coefficient of 0.070 mm² h⁻¹. In addition, the composition shows a lower diffusion coefficient with respect to those reported so far for a Fricke dosimeter. The total uncertainty of the estimated doses for the Fricke dosimeter was 3.96% at 95% confidence level.

In the MARE experiment onboard the NASA Artemis 1 mission of the ORION spacecraft to lunar orbit, two anthropomorphic female phantoms, equipped with a large number of active and passive radiation detectors were flown. Among the detectors were both LiF:Mg,Ti and LiF:Mg,Cu,P TL detectors as well as Al₂O₃:C OSL detectors. In order to correctly interpret the measured doses, the effective relative TL/OSL efficiency for cosmic radiation of these detectors was calculated by combining simulated radiation spectra for the cis-lunar space conditions with the efficiency functions based on experimental data for different ions and on a microdosimetric model.

The obtained results show that for the ORION shielding conditions, the relative efficiency of LiF:Mg,Ti is close to unity (0.95), while the remaining detectors show somewhat smaller efficiency: 0.90 for Al₂O₃:C and (0.81–0.86) for LiF:Mg,Cu,P. The analysis of the influence of the shielding thickness on the relative TL/OSL efficiency revealed, that for low shielding conditions, the relative efficiency may be more significantly decreased, reaching values between 0.71 (LiF:Mg,Cu,P) and 0.85 (LiF:Mg,Ti) for 1 g/cm².

Luminescence-based thermometry and dating often requires determination of the saturation level for specific signals and the corresponding dose. However, previous studies found non-monotonic dose responses for some monochromatic thermoluminescence (TL) and optically stimulated luminescence (OSL) signals from quartz as well as spectral overlap of emission bands, substantially complicating data interpretation. Therefore, the present study examines (1) the variability in the TL emission spectrum of quartz and feldspar from bedrock and sediment of different provenances and, (2) the saturation characteristics of the blue emission band for both quartz and feldspar in the dose range from 0.25 kGy to 50 kGy. The experimental results confirm differences in the spectra which appear to be characteristic of their geological origin and chemical composition. Spectral analysis shows that in the temperature range 175–220 °C the blue emission band at ∼2.5 eV dominates over other bands for all quartz samples studied. A broad UV-blue TL signal peaking at ∼2.5−3.0 eV and composed of probably three overlapping, individual bands is characteristic for K-feldspar, while one Na-feldspar exhibits an additional band at ∼2.2 eV.

In the studied dose range, the emissions at ∼2.5 eV and ∼2.6 eV increase as a function of dose up to 6 kGy for both quartz and feldspar. A difference in dose response was observed for high doses (>6 kGy) where feldspar samples reached a stable saturation level while for quartz the blue emission band intensity decays until 50 kGy after having attained a maximum. Our results suggest the suitability of feldspar TL for palaeothermometry and thermochronometry from the perspective of signal saturation characteristics. However, the spectral overlap of several bands in the UV-blue emission requires careful optical filter selection to isolate the signal of interest. The non-monotonic dose response of the ∼2.5 eV emission of quartz around 200 °C glow curve temperature probably precludes its use for temperature sensing based on relative trap saturation levels.

X-rays generated by high-energy pulsed electron sources can be utilized in tumor treatment. The time spectrum measurement of pulsed electron sources enables precise treatment and provides feedback to the design and construction of accelerators. In this paper, silica aerogel samples of different densities and thicknesses were prepared as Cherenkov radiator. The transmittance and refractive index of these samples were measured, then the absorption and scattering lengths were calculated on the basis of the obtained transmittance. The obtained results were input into Geant4 software to get the intrinsic luminescence time of the silica aerogel of different densities and thicknesses. Finally, a measurement system was constructed with the silica aerogel samples, and the rise time of this system and the silica aerogel were measured by using a picosecond electron accelerator. The results demonstrate that the rise time of the measurement system is below 180 ps and that of the silica aerogel is less than 54.32 ps. It is also proved that the silica aerogel can be used as the Cherenkov radiator for the measurement of the time spectrum of high-energy pulsed electron sources.

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.