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Activity of 225Ac was measured by the digital anti-coincidence spectroscopy technique using a 4πα–γ detector configuration, composed of a sandwich type 4π plastic scintillator and Ge detectors. Ultrathin plastic scintillators were used for selective detection of α-particles emitted from 225Ac and its progenies, and the α-counting efficiencies of a 4π plastic scintillation detector for individual nuclides in the decay chain were determined as well. A list-mode multichannel analyzer was employed to record coincidence/anti-coincidence events for off-line analyses. The time difference distribution spectra revealed α-particle emission following 213Po decay without β-particle interference from 213Bi. • Selective α-particle detection using ultrathin plastic scintillators for 225Ac. • Individual α-efficiencies determined by 4πα(PS)–γ(Ge) anti-coincidence spectroscopy. • α-particles from short-lived 213Po(T 1/2 = 3.7 μs) detected without interference. • Effect of β-particle from 213Bi confirmed from γ–α/β time difference distribution. • Results were consistent with those obtained using the CN method with LSC. [ABSTRACT FROM AUTHOR]

A network of specialist laboratories support the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) with re-measurements of radionuclide samples, including xenon gas. The measurement of four xenon fission product radionuclides ( 133 Xe, 135 Xe, 131m Xe and 133m Xe) can be used to detect an underground nuclear explosion. Laboratories use a range of techniques to measure the radionuclides, including beta-gamma (β − γ) coincidence spectrometry. These highly-sensitive measurements are capable of detecting concentrations of down to 500 atoms of 133 Xe in a few cm 3 of xenon. In some detector systems, detection of the metastable isomers ( 131m Xe and 133m Xe) can be more challenging due to interferences between the signatures of different radionuclides. Recent work has shown that using high-purity Germanium (HPGe) high-resolution gamma detectors, these interferences can be reduced, lowering the dependence of the detection limits on radionuclide sample isotopic composition. One downside of these detectors is the reduction in detection efficiency, which impacts the overall detection sensitivity; so assessing different detector systems is a priority for radionuclide laboratories. This work presents a coincidence detector system comprising of a plastic scintillator gas cell and a large-crystal high-purity germanium detector. The energy resolution, coincidence detection efficiency, MDA and interference factors are determined from measurements of synthetic radioxenon gas samples. • A plastic scintillator and HPGe β − γ coincidence system has been configured for the measurement of isotopes of radioxenon • Calculations show that this type of setup can improve the detection limits compared to other systems. • High-resolution γ -detectors can separate Xe and Cs X-rays, decreasing interference. [ABSTRACT FROM AUTHOR]

X-ray transmission imaging (XRT) is widely used for sorting materials. However, conventional single-energy and dual-energy X-ray systems have poor ability to discriminate between materials with similar atomic number (Z), and the count rate of available multi-energy XRT detectors could not support high-speed industrial applications. This paper presents the design of a detector that can potentiality achieve high-speed multi-energy X-ray imaging using Geant4 simulations. This detector consisted of five detection layers (with three scintillator materials: CsI, GOS and CdWO 4), two metal filters, which allows X-ray imaging at five energies. Validation simulation showed that the 15% more accurate than a dual-layers detector in the classification of Mg and Al alloys. • A five-layer structure scintillator imaging detector was designed using Geant4 simulations. • The energy response in each layer of this detector is clearly differentiated, permitting multi-energy X-ray imaging. • The readout equipment employed in dual-layer detectors can be used in a five-layers detector with the same imaging speed. • Stimulations showed that this imaging system can be used to differentiate between materials with similar atomic numbers, such as Mg and Al alloys. [ABSTRACT FROM AUTHOR]

Dose-rate monitoring instruments measure the ambient dose equivalent and hence are crucial for protecting workers from radiation exposure. Although plastic scintillation detectors (PSDs) are ideal equipment for dosimetry, they are rarely used owing to the lower detection efficiency than other scintillation detectors. In this study, we acquired ten types of G(E) functions to utilize a PSD in spectroscopic dosimetry using the least-square and first-order methods. The energy response of PSD was much improved in terms of dose evaluation. • Measurement of ambient dose equivalent using a plastic scintillation detector. • Detector with an EJ-276G plastic scintillator coupled to a silicon photomultiplier. • G(E) function obtained using the least-square and first-order methods. • Ensemble G(E) function showed the most stable and superior performance. [ABSTRACT FROM AUTHOR]

The dosimetry of small fields has become tremendously important with the advent of intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery, where small field segments or very small fields are used to treat tumors. With high dose gradients in the stereotactic radiosurgery or radiotherapy treatment, small field dosimetry becomes challenging due to the lack of lateral electronic equilibrium in the field, x-ray source occlusion, and detector volume averaging. Small volume and tissue-equivalent detectors are recommended to overcome the challenges. With the lack of a perfect radiation detector, studies on available detectors are ongoing with reasonable disagreement and uncertainties. The joint IAEA and AAPM international code of practice (CoP) for small field dosimetry, TRS 483 (Alfonso et al., 2017) provides guidelines and recommendations for the dosimetry of small static fields in external beam radiotherapy. The CoP provides a methodology for field output factor (FOF) measurements and use of field output correction factors for a series of small field detectors and strongly recommends additional measurements, data collection and verification for CyberKnife (CK) robotic stereotactic radiotherapy/radiosurgery system using the listed detectors and more new detectors so that the FOFs can be implemented clinically. The present investigation is focused on using 3D gel along with some other commercially available detectors for the measurement and verification of field output factors (FOFs) for the small fields available in the CK system. The FOF verification was performed through a comparison with published data and Monte Carlo simulation. The results of this study have proved the suitability of an in-house developed 3D polymer gel dosimeter, several commercially available detectors, and Gafchromic films as a part of small field dosimetric measurements for the CK system. • Different commercial small field detectors are used to measure the field output factors for robotic CyberKnife system. • Tissue equivalent radiochromic EBT3 films were calibrated, and measurements of field output factor are performed. • Locally fabricated and patented 3D polymer is also used to measure the field output factors for CK. • The measured data were compared with Monte Carlo simulated data using BEAMnrc and DOSRZnrc codes. • The measured field output factors with all the detectors and techniques are found suitable for CK. [ABSTRACT FROM AUTHOR]

Combination of two or three dissimilar scintillator materials as a radiation detector has found major role in environmental radiation monitoring. In this paper, a three-layer Phoswich detector including BC-400, YAG, and CsI was designed to efficiently discriminate gamma-ray in the beta events up to 3.2 MeV using a simple rise-time discrimination method. MCNPX Monte Carlo code was used to obtain interaction probability of beta and gamma-rays as well as optimum thicknesses of the layers in the designing process. The optical transport of the system was simulated by GEANT4. In this regard, the pulses from simultaneous beta-gamma emitter sources were detected and discriminated based on pulse's rise-time so that the minimum number of gamma-ray contaminating events was observed in the beta spectrum. The results showed that using the proposed configuration and the method, output pulses with a rise-time shorter than 9 ns have been successfully detected as a beta particle while those with rising time longer than 15 ns have been identified as gamma-ray events. Overall results revealed that using the proposed system, an individual spectrum of beta particles or gamma-rays can be recorded from a simultaneous beta-gamma emitter source that minimizes contribution of the other radiation. • A Phoswich detector was designed for simultaneous beta-gamma radiation. • Scintillator materials used in the detector structure should have different decay time constant. • GEANT4 simulation was used for scintillation lights transport. • A pulse discrimination method based on the pulse rise time has been proposed for pulse processing. • Beta-rays were successfully discriminated against gamma-rays by the proposed detector and associated pulse processing method. [ABSTRACT FROM AUTHOR]

Neutron gamma density measurement using dual gamma detectors (NGD-GD) is a popular density measurement method. Compared with other NGD methods, the NGD-GD method has many advantages in tool optimization, cost control, and density precision; however, it is easily affected by the salinity of formation water. To improve the NGD-GD method, the influence mechanism of formation water salinity was discussed, and a feasible improvement scheme using characteristic gamma information was proposed. A special boron sleeve gamma detector was designed to record the capture gamma rays from the boron-10 element. By analyzing the gamma spectrum, pure boron-10 gamma information was extracted from the total capture gamma spectrum for density calculation. Finally, a new NGD method with boron sleeve gamma detectors (NGD-BD) was developed. Results depict that although the NGD-BD method has a slight decrease in density accuracy and precision compared with the NGD-GD method, its performance is significantly improved in high-brine formations, and oil and gas formations. In addition, the NGD-BD method exhibits better performance in terms of density accuracy, density precision, and environmental impact than another NGD method that uses hydrogen capture gamma information. Moreover, the NGD-BD method is easily implemented with low cost and has little impact on existing NGD tools, and hence, it can coexist with other NGD methods to improve logging quality. Overall, the NGD-BD method is a very promising alternative to the NGD-GD method. [ABSTRACT FROM AUTHOR]