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High energy X-ray non-destructive testing technology can obtain the internal structure information of the inspected object without destroying it. The multi-rod-beam nature of nuclear fuel assemblies can lead to severe scattering ray effects，which can degrade image quality. In order to correct the interference of scattering ray，this study analyzed the limitations of various methods to solve the interference of scattered rays in the non-destructive testing of nuclear fuel assemblies. Geant4 is used to simulate the nondestructive testing process of nuclear fuel components，and ComptonFlag class is constructed to mark the scattered rays of Compton scattering and remove their interference. The simulation results show that the CNR of defective and intact components in the projection image is increased by 69.02% after the scattering ray interference is removed，which can effectively improve the image quality of non-destructive testing of nuclear fuel assemblies.

The conflict between the production capacity and demand for medical radioisotopes has become more prominent. In addition, for some new types of medical radioisotopes, neutron, and proton-induced reactions are not the best way to generate them with high specific activity. The research status of medical radioisotopes is introduced, then the gamma facility and potential new medical radioisotope candidates based on photonuclear reaction are widely surveyed. The production of medical radioisotope 186 g Re is simulated based on the Laser Compton Scattering (LCS) gamma source and bremsstrahlung gamma source. It is found that the next generation quasi-monochromatic, high-flux LCS gamma source can produce medical radioisotope 186 g Re with less than 0.05% 188Re impurity with around 400 mb cross section. Meanwhile, the bremsstrahlung gamma source can produce around 200 MBq/g specific activity medical radioisotope 186 g Re with realistic electron intensity 3.125 mA. This study and simulations show that photonuclear reaction can be regarded as an alternative route for producing medical radioisotopes. • Study on photonuclear method for high-specific-activity medical isotopes. • Provided a wide survey of potential gamma transmutation medical radioisotopes. • Explored strengths of quasi-monoenergetic and bremsstrahlung γ for 186gRe production. [ABSTRACT FROM AUTHOR]

This study aims to formulate semi-empirical processing applied to analyze simulated and experimental scattering spectra on pipeline samples for estimating the intensity of the single scattering component for the Compton scattering technique. Firstly, a procedure has been developed based on probability density functions of each scattering component, which are obtained by GEANT4. Secondly, sixteen targets are simulated with MCNP6 to validate the proposed procedure. It is shown that the relative deviation for all samples is under 3%. Thirdly, the nine calculated thickness of pipeline samples is determined with a maximum relative deviation lower than 5% in comparing to calibration thickness. [ABSTRACT FROM AUTHOR]

The production, application, and/or measurement of polarised X-/gamma rays are key to the fields of synchrotron science and X-/gamma-ray astronomy. The design, development and optimisation of experimental equipment utilised in these fields typically relies on the use of Monte Carlo radiation transport modelling toolkits such as Geant4. In this work the Geant4 "G4LowEPPhysics" electromagnetic physics constructor has been reconfigured to offer a best set of electromagnetic physics models for studies exploring the transport of low energy polarised X-/gamma rays. An overview of the physics models implemented in "G4LowEPPhysics", and it's experimental validation against Compton X-ray polarimetry measurements of the BL38B1 beamline at the SPring-8 synchrotron (Sayo, Japan) is reported. "G4LowEPPhysics" is shown to be able to reproduce the experimental results obtained at the BL38B1 beamline (SPring-8) to within a level of accuracy on the same order as Geant4's X-/gamma ray interaction cross-sectional data uncertainty (approximately ± 5 %). [ABSTRACT FROM AUTHOR]

Compton scatter imaging (CSI) is a promising, noninvasive imaging technique; however, it is limited by its poor utilization of X-rays and its bad image signal-to-noise ratio (SNR). In this work, a novel method combining push-broom CSI with coded-aperture imaging was devised to improve the utilization of backscattered X-rays and the image SNR. Firstly, the principles of coded-aperture push-broom CSI are illustrated, and its various applications are discussed. Then, simulations of a point source and a line source are performed to validate its feasibility. It was discovered that the inherent coding noise trends for the mask and the antimask were the opposite of each other. Therefore, these coding noises could be offset by averaging the two. Furthermore, a system prototype was built to scan objects, such as point phantoms, line phantoms, character phantoms of "IHEP", and other typical samples. Compared with traditional push-broom CSI, this novel system obtained a better backscatter image with lower X-ray power and at a farther distance. This feature is important for system miniaturization and radiation dose reduction. Although optimizations should be considered in the future, this approach demonstrates useful application potential. • We devise a novel method of coded-aperture push-broom Compton scatter imaging. • It improves the utilization of backscattered X-rays and the image SNR. • It shows a potential for system miniaturization and radiation dose reduction. • Noises could be offset mostly by averaging results of mask and antimask. • Simulations and experiments support the method well. [ABSTRACT FROM AUTHOR]

The total mass attenuation coefficients (μ/ρ) of oxide dispersion strengthened (ODS) steels have been investigated by using Geant4 simulation toolkit at energies ranging from 0.01 MeV to 100 GeV. Moreover, Geant4 is applied to further study on the partial mass attenuation coefficient of three main interactions including photoelectric effect, compton scattering, gamma conversion between incident photon and ODS steels. Then molecular cross-section (σ m) and mean free path (λ) are obtained by the total mass attenuation coefficients. The results obtained by Geant4 are compared with those obtained by experiments and XCOM program and these results agree with each other very well. It is concluded that Geant4 Monte Carlo toolkit is a powerful tool in studying interaction of photons in material and energies. The shielding parameters of ODS steels presented in this paper can be very useful for the potential nuclear application and other industries in future. • The μ/ρ of ODS steels have been studied by Geant4 at energies from 0.01 MeV to 100 GeV. • The results gained by Geant4 agree with those gained by experiments and XCOM well. • The partial μ/ρ of three main interactions between photon and ODS steels are studied. [ABSTRACT FROM AUTHOR]

Abstract Compton γ -ray sources have been in operation for over 30 years with new facilities being under construction or proposed. The gamma beam system under implementation at the Extreme Light Infrastructure - Nuclear Physics facility in Romania will deliver brilliant γ -ray beams with energies up to 19.5 MeV. Several instruments for measuring the parameters of the γ -ray beam are under development at ELI-NP. One of these instruments based on a High Purity Germanium detector is routinely used for beam energy measurements at other facilities. Here we investigate the use of a High Purity Germanium detector to continuously monitor the intensity of the ELI-NP gamma beam by measuring the inelastic scattering of photons. This method relies on both experimental and simulated data and it has been successfully tested during a recent experiment at the High Intensity γ -ray Source facility. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a novel Compton scattering tomography (CST) method using an annular detector for measuring density variations was proposed. The purpose of this study is to improve the collection efficiency of traditional CST and to significantly reduce the detection time down to minutes per voxel. The simulation setup was built in the GEANT4 software. Monte Carlo simulations were performed, revealing a depth positioning accuracy of ±0.5 mm for flaw and inclusion inspection and a tomographic resolution better than 2 mm. [ABSTRACT FROM AUTHOR]

This paper presents X-ray spectra of channeling radiation expected at the FAST (Fermi Accelerator Science and Technology) facility in Fermilab. Our purpose is to produce high brightness quasi-monochromatic X-rays in an energy range from 40 keV to 110 keV. We will use a diamond crystal and low emittance electrons with an energy of around 43 MeV. The quality of emitted X-rays depends on parameters of the electron beam at the crystal. We present simulations of the beam optics for high brightness and high yield operations for a range of bunch charges. We estimate the X-ray spectra including bremsstrahlung background. We discuss how the electron beam distributions after the diamond crystal are affected by channeling. We discuss an X-ray detector system to avoid pile-up effects during high charge operations. [ABSTRACT FROM AUTHOR]

In the field of nuclear medicine, nuclear security and astrophysics, Compton imaging is a promising technique for gamma-ray source imaging. We are developing a Compton imager using two layers of CdZnTe pixel array detectors. In this paper, the backward-scattering effect within such imagers is numerically studied using Geant4 Monte Carlo Package. From images reconstructed based on forward-scattering and backward-scattering imaging events, the imaging precision was investigated in a comparative analysis, in regard to energy resolution and position resolution. Furthermore, to establish a method to use backward-scattering imaging events properly so that the imaging efficiency can be significantly improved, the difference between reconstruction from forward-scattering and backward-scattering imaging events was analyzed to uncover a causal mechanism. [ABSTRACT FROM AUTHOR]

PoGOLite is a balloon-borne hard X-ray polarimeter dedicated to the study of point sources. Compton scattered events are registered using an array of plastic scintillator units to determine the polarisation of incident X-rays in the energy range 20–240 keV. In 2013, a near circumpolar balloon flight of 14 days duration was completed after launch from Esrange, Sweden, resulting in a measurement of the linear polarisation of the Crab emission. Building on the experience gained from this Pathfinder flight, the polarimeter is being modified to improve performance for a second flight in 2016. Such optimisations, based on Geant4 Monte Carlo simulations, take into account the source characteristics, the instrument response and the background environment which is dominated by atmospheric neutrons. This paper describes the optimisation of the polarimeter and details the associated increase in performance. The resulting design, PoGO+, is expected to improve the Minimum Detectable Polarisation (MDP) for the Crab from 19.8% to 11.1% for a 5 day flight. Assuming the same Crab polarisation fraction as measured during the 2013 flight, this improvement in MDP will allow a 5 σ constrained result. It will also allow the study of the nebula emission only (Crab off-pulse) and Cygnus X-1 if in the hard state. [ABSTRACT FROM AUTHOR]

In beam geometries where a directed γ -ray beam hits the surface of a coaxial high purity germanium detector (HPGe), the detector efficiency is sensitive to the position where γ -rays initially hit the detector surface because the structure of the detector is nonuniform. This may cause inaccuracy of the detector efficiency when measured using standard sources that are point-like sources emitting γ -rays isotropically. Obtaining a precise estimation of the full energy peak efficiency of the coaxial HPGe detector in the beam geometry for on-axis and off-axis measurements requires a Monte Carlo simulation. We performed Monte Carlo simulations that calculate the detector efficiency in the beam geometry. The effects of the off-axis distance and γ -ray beam size on the efficiency are quantitatively analyzed. We found that the intrinsic efficiency in the beam geometry is maximized when the beam hits the detector at specific off-axis distances. Our Monte Carlo calculations have been supported by nuclear resonance fluorescence experiments using laser Compton scattering γ -ray beams. • Calculating efficiency of coaxial HPGe detector for directed γ-ray beams by Geant4. • Revealing the sensitivity of efficiency to γ-ray beam size and off-axis distance. • Off-axis efficiency is higher than on-axis efficiency, depending on γ-ray energy. • Maximizing efficiency by selecting the optimum off-axis distance. • LCS γ-ray beams up to 3 MeV validate calculations experimentally. [ABSTRACT FROM AUTHOR]

This work compares two popular MC simulation frameworks ROSI (Roentgen Simulation) and GEANT4 (Geometry and Tracking in its fourth version) in the context of X-ray physics. The comparison will be performed with the help of a parameter study considering energy, material and length variations. While the total deposited energy as well as the contribution of Compton scattering show a good accordance between all simulated configurations, all other physical effects exhibit large deviations in a comparison of data-sets. These discrepancies between simulations are shown to originate from the different cross sectional databases used in the frameworks, whereas the overall simulation mechanics seem to not have an influence on the agreement of the simulations. A scan over energy, length and material shows that the two parameters energy and material have a significant influence on the agreement of the simulation results, while the length parameter shows no noticeable influence on the deviations between the data-sets. [ABSTRACT FROM AUTHOR]

In this work, we propose a semi-empirical method for determining the thickness of pipe-wall, of which the determination is performed by combining the experimental and Monte Carlo simulation data. The testing measurements show that this is an efficient method to measure the thickness of pipe-wall. In addition, this work also shows that it could use a NaI(Tl) scintillation detector and a low activity source to measure the thickness of pipe-wall, which is simple, quick and high accuracy method. [ABSTRACT FROM AUTHOR]

Abstract: A depth discrimination method is devised based on a multirow linear array detector for push-broom Compton scatter imaging. Two or more rows of detector modules are placed at different positions towards a sample. An improved parallel-hole collimator is fixed in front of the modules to restrict their fields of view. The depth information could be indicated by comparing the signal differences. In addition, an available detector and several related simulations using GEANT4 are given to support the method well. [Copyright &y& Elsevier]

The performance of a radiation shielding system for a hyper-pure germanium detector has been characterised for Terrestrial radiation sources, Cosmic muons, X-ray fluorescence and the Compton scattering of source photons. Several methods to reduce the background seen are quantified, including increasing the inner radius of the Pb cave, and increasing the thickness of the shielding. Substantial improvements in the reduction of fluorescence X-rays are found to be achievable by modifying the liner thicknesses used. Increasing the Sn liner from 1.5 to 2.5 mm will increase the shielding of Pb X-rays from 95 to 99.5 %. Reducing the Cu liner from 1.0 to 0.5 mm maintains a 99.5 % level of shielding for Sn/Cd X-rays, however it greatly reduces the amount of Compton scattering of source photons into the detector (a process that is shown to cause an order of magnitude more events in the background than X-ray fluorescence). Cosmic muons were found to increase the amount of background radiation seen, both through direct interaction and the production of secondary radiation. The Cosmic muon contribution, however, was found to produce a much smaller effect than that caused by Terrestrial radiation and Compton scattered photons/fluorescence from the source. The total level of background radiation entering the detector chamber was found to decrease up to the full 200 mm of Pb shielding simulated. [ABSTRACT FROM AUTHOR]

Abstract: In this work we present an active Compton scattering polarimeter as a focal plane instrument able to extend the X-ray polarimetry towards hard X-rays. Other authors have already studied various instrument design by means of Monte Carlo simulations, in this work we will show for the first time the experimental measurements of “tagging efficiency” aimed to evaluate the polarimeter sensitivity as a function of energy. We performed a characterization of different scattering materials by measuring the tagging efficiency that was used as an input to the Monte Carlo simulation. Then we calculated the sensitivity to polarization of a design based on the laboratory set-up. Despite the geometry tested is not optimized for a realistic focal plane instrument, we demonstrated the feasibility of polarimetry with a low energy threshold of 20keV. Moreover we evaluated a minimum detectable polarization of 10% for a 10mCrab source in 100ks between 20 and 80keV in the focal plane of one multilayer optics module of NuSTAR. The configuration used consisted of a doped p-terphenyl scatterer 3cm long and 0.7cm of diameter coupled with a 0.2cm thick LaBr3 absorber. [Copyright &y& Elsevier]

A Monte Carlo approach was used to study the effects of Doppler energy broadening on Compton camera performance. The GEANT4 simulation toolkit was used to model the radiation transport and interactions with matter in a simulated Compton camera. The low energy electromagnetic physics model of GEANT4 incorporating Doppler broadening developed by Longo et al. was used in the simulations. The camera had a 9 × 9 cm scatterer and a 10 × 10 cm absorber with a scatterer to-absorber separation of 5 cm. Modelling was done such that only the effects of Doppler broadening were taken into consideration and effects of scatterer and absorber thickness and pixelation were not taken into account, thus a 'perfect' Compton camera was assumed. Scatterer materials were either silicon or germanium and the absorber material was cadmium zinc telluride. Simulations were done for point sources 10 cm in front of the scatterer. The results of the simulations validated the use of the low energy model of GEANT4. As expected, Doppler broadening was found to degrade the Compton camera imaging resolution. For a 140.5 keV source the resulting full-width-at-half-maximum (FWHM) of the point source image without accounting for Doppler broadening and using a silicon scatterer was 0.58 mm. This degraded to 7.1 mm when Doppler broadening was introduced and degraded further to 12.3 mm when a germanium scatterer was used instead of silicon. But for a 511 keV source, the FWHM was better than for a 140 keV source. The FWHM improved to 2.4 mm for a silicon scatterer and 4.6 mm for a germanium scatterer. Our result for silicon at 140.5 keV is in very good agreement with that published by An et al. [ABSTRACT FROM AUTHOR]

The aim of this work is as using AIDA implementation in Geant4 to analyze some characteristics of Compton interaction of gamma ray in germanium for incident energy of photons of 1-2MeV. So we verify starting points of algorithms for tracking reconstruction, both back-tracking and forward-tracking algorithms. We have generated a set constructed with interaction points and we found that this set scale with Hurst exponent 0.48. [ABSTRACT FROM AUTHOR]

Abstract: A gamma-ray beam produced by Compton scattering of a laser beam with a relativistic electron beam has been used for nuclear physics research at the high intensity -ray source () facility at Duke University. The success of many experiments using the gamma-ray beam critically depends on the accurate knowledge of the gamma-ray beam energy distribution which is typically obtained by unfolding a measured energy spectrum. Conventionally, the detector response function used in the spectrum unfolding is simulated by a simple Monte Carlo code in which an isotropic gamma-ray event generator is used. However, for a Compton scattered gamma-ray beam, this simulation method could lead to an inaccurate detector response function, since it neglects the spatial and energy distributions of the gamma-ray beam. In this paper, we will present a novel end-to-end gamma-ray spectrum reconstruction method by completely modeling the process of the Compton gamma-ray beam production, collimation, transportation and detection. Using this method, we have successfully reconstructed the energy distribution of beams for nuclear physics research with a high degree of accuracy. [Copyright &y& Elsevier]