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Total, whole-atom, individual and integrated Compton scattering cross sections and Compton energy absorption scattering cross sections are evaluated for light elements, such as, H, C, N, O, P, and Ca, with relativistic impulse approximation methods. Most of the phantom materials composed of these elements, which are the basic constituents of biological soft-tissue and attenuation through them, provides potential source of information. Compton scattering cross-sections for few biological materials, such as, H 2 O, C 2 H 4 , C 8 H 8 , C 5 H 8 O 2 , C 6 H 11 NO, C 16 H 14 O 3 , C 55 H 102 O 6 , [Ca 3 (PO 4)] 3 Ca (OH) 2 of medical interest, have been evaluated with the use of double differential scattering cross-section based on impulse approximation. Utilized these values to evaluate the Compton energy absorption cross sections and Compton component of mass energy absorption coefficients (cm2/g) in the energy region from 0.005 to 10 MeV. The derived results are compared with the theoretical tabulations. • Evaluation of double differential scattering cross-section based on impulse approximation. • Total, whole-atom, individual and integrated Compton scattering cross sections. • Compton energy absorption scattering cross sections. • Compton scattering cross-sections for few biological materials. • Compton component of mass energy absorption coefficients. [ABSTRACT FROM AUTHOR]

Different kinds of nanoparticles have been widely studied for biomedical purposes, including applications like dose enhancement in radiotherapy treatments and contrast agent in radiological studies. Recent work suggests that gold nanoparticles can be used as contrast agents in K-edge imaging and X-ray Fluorescence Computed Tomography, mainly due to their high K-edge energy value and good biocompatibility. However, the gold X-ray fluorescence (XRF) signal obtained in these procedures is relatively week when compared with Compton or bremsstrahlung radiation emitted in the surrounding tissues, mainly because it is not possible to achieve large gold nanoparticles concentrations within biological tissues added to the XRF is attenuated by other tissues when leaving the patient body. This work presents a feasibility study on implementation of FLUKA, PENELOPE and MCNP6 Monte Carlo codes to model the detection of gold XRF emitted by a small volume containing different gold concentrations and located at different depths in a tissue-equivalent phantom. Results indicate that there is good agreement between PENELOPE and FLUKA for gold Kα and Kβ lines estimations when highly symmetric simulation scenario and kilovoltage X-ray beam were used, achieving differences lower than 2%; however, differences up to 6 times were observed between FLUKA and MCNP6 under the same conditions. In addition, remarkable differences were obtained when megavoltage X-ray beam was used, being up to 11 times between PENELOPE and FLUKA and up to 4 times between FLUKA and MCNP6 for gold Kα and Kβ lines estimations. In this regard, a suitable normalization method was proposed and implemented to perform cross-comparisons of XRF estimations obtained from the Monte Carlo codes. By means of the proposed method, FLUKA, PENELOPE and MCNP6 can be successfully implemented to assess which configuration (gold concentration and target volume depth) leads to a better detection of gold XRF, despite differences in XRF estimation between the codes. • FLUKA, PENELOPE and MCNP6 codes were used for gold XRF estimation. • Scenarios representing small tumor volumes marked with gold were studied. • X-ray beams for Radiology and Radiotherapy energy ranges were investigated. • FLUKA, PENELOPE and MCNP6 estimations of gold XRF do not agree with each other. • A normalization method was proposed for cross-comparison of Monte Carlo estimations. [ABSTRACT FROM AUTHOR]

A Compton suppression system (CSS), which plays an important role in γ-ray diagnostics, has been developed to acquire the γ-ray emission spectra generated in the HL-2A tokamak plasma. It takes advantages of the anti-coincidence method of two branches of γ-ray signals, one is from a high purity germanium (HPGe) detector, and the other from several bismuth germinate (BGO) detectors, to output the suppressed spectra. In the present paper, a Geant4 simulation, together with its subsequent data processing which took accidental coincidences into account, was performed to study the detection efficiencies of the CSS for γ-rays with energies between 0.2 and 13 MeV. Calculation results showed that there were small detection efficiency differences between the unsuppressed and suppressed spectra when HPGe count rates were smaller than 105 cps, and the area ratios of additional peaks to their corresponding full energy peaks were not associated with HPGe count rates. Based on the calculation results, the empirical formulas of detection efficiencies of the CSS were put forward. Finally, after the experimental verification of the empirical formulas, a suppressed γ-ray spectrum acquired by the CSS during 2018 HL-2A experiment campaign was unfolded using the detection efficiencies. This work makes it possible for the analyses of the γ-ray emission spectra generated from the HL-2A tokamak. • The detection efficiencies of the Compton suppression system at the HL-2A tokamak have been calculated using Geant4. • The detection efficiency calculations with Geant4 have taken accidental coincidences into account. • The empirical formulas of detection efficiencies of the Compton suppression system have been put forward. [ABSTRACT FROM AUTHOR]

Considered an important hydrological and geomorphological agent, fire can cause physical, chemical and biological changes in the soil. Besides wildfire, the study of fire effects is also related to traditional agriculture. This study presents the characterization and analysis of soil samples submitted to burn simulation with the objective to build a temperature prediction model in order to determine the maximum temperature reached by real soil burn samples. For this purpose, surface soil samples (0–2.5 cm) classified as Haplic Cambisol were collected from a native forest area close to the studied field. The temperature of the simulation samples ranged from 50 to 750 °C. Moreover, a real burn set of samples were measured for temperature prediction using the proposed model. The characterization and quantification of the chemical elements present in the soil were done by Energy Dispersive X-ray Fluorescence (EDXRF) measurements. Plots with Fe concentration and with the Rayleigh and Compton scattering data versus temperature were constructed. The Fe/Rh and Fe/RhC ratios resulted in relative deviations ranging from 14% to 22% using univariate analysis. Multivariate analysis was also applied through partial least squares regression (PLSR) method in four different spectrum regions. The best result was obtained for the model using the spectrum scattering region with r2 = 0.90 and relative deviation ranging from 8% to 25% for the predicted temperature. The use of local multivariate PLSR models improved the results when compared to the univariate regression results. • EDXRF data from soil measured after a prescribed fire was applied for maximum temperature prediction. • Modeling with Fe concentration and X-ray scattering conducted to reliable results. • Maximum temperature in prescribed real burn were estimated post-fire. [ABSTRACT FROM AUTHOR]

Abstract The NaI(Tl) detector has become the main way of research and application of in-situ radioactivity measurement in the marine environment due to many advantages on detection efficiency, power consumption, cost and applicability. But for the poor energy resolution and there is a high background in the low energy region of the spectrum measured mainly originating from the Compton scattering of natural radionuclides such as 40K with high concentrations in seawater, it is difficult and also an interesting topic for NaI(Tl) detector to identificate the radionuclides and calculate them in seawater by analyzing the spectra measured. In this paper, an in situ NaI(Tl) detector developed for the marine environment was energy, resolution and efficiency calibrated. The detection response matrix was calculated by taking all the responsible processes and interactions of gamma rays in water as well as in the detector into account using Monte Carlo simulation method. And then an improved Richardson-Lucy (R-L) deconvolution algorithm was proposed to reconstruct the gamma spectrum measured in the seawater to remove as efficiently as possible the background counts into the corresponding photopeaks. The original spectrum was transformed from poor energy resolution to the corresponding deconvolution spectrum of the high energy resolution with several isolated photopeaks. The experiments of synthetic spectrum and measured spectrum both showed promising results for the radionuclide qualitative and quantitative analysis. Highlights • The detector developed and its calibration is given. • Simulation method for marine radioactivity measurement is discussed. • Detection response matrix is established. • TImproved Richardson-Lucy deconvolution method is proposed for spectrum analysis. • Continue research method is discussed. [ABSTRACT FROM AUTHOR]

Gamma detector detection technology based on NaI(Tl) scintillation crystal has become a popular research topic and has been applied in the field of marine radioactive environment automatic monitoring because of its advantages of low power consumption, low cost and strong environmental adaptability. However, insufficient energy resolution of the NaI(Tl) detector and great Compton scattering in the low-energy region caused by the abundance of natural radionuclides in seawater hinder the automatic analysis of radionuclides in seawater. This study adopts the combination of theoretical derivation, simulation experiment, water tank test and seawater field test, establishing an effective and feasible spectrum reconstruction method. The measured spectrum in seawater is regarded as the output signal formed by the convolution of the incident spectrum and the detector response function. The acceleration factor p is introduced to construct the Boosted-WNNLS deconvolution algorithm, which is used to iteratively reconstruct the spectrum. The analysis results of the simulation test, water tank test and field test meet the radionuclide analysis speed and accuracy requirements for the in-situ automatic monitoring of seawater radioactivity. The spectrum reconstruction method in this study converts the physical problem of insufficient detection accuracy of spectrometer in the practical application into a mathematical problem of deconvolution solution, restores the original radiation information in seawater, and improves the resolution of the seawater gamma spectrum. • The detector structure diagram is given. • Spectrum analytical method for marine radioactivity measurement is studied. • The response matrix construction method is discussed. • The Boosted-WNNLS deconvolution algorithm is constructed for the radionuclide analysis. • The marine field experiment is carried out. [ABSTRACT FROM AUTHOR]

The accuracy of activity determination for activated nuclide 56Mn is the key to the manganese bath method applying to the characterization of radionuclide neutron source. As an alternative to the 4π(Č)-γ method, TDCR-Čerenkov method could also be applied to the measurement of 56Mn in the manganese bath device, if the existing calculation model is extended. There are two difficulties when the existing TDCR-Čerenkov method is applied to the activity determination of 56Mn. One is that the efficiency computation of gamma transitions, and the other is the interference contributed by Čerenkov photons emitted in the photomultiplier windows induced by Compton scattering. In this study, the above two difficulties are solved by extending the calculation model. For efficiency computation, the decay scheme of 56Mn is taken into account in the calculation of efficiency. Among them, the efficiency of gamma transition is calculated from the simulated secondary electronic spectra. In addition, Čerenkov photons emitted in photomultiplier windows are corrected by additional light proof experiment and improved calculation model. The results derived from this extended method are in good agreement with other standardization technique. • 56Mn is measured by means of TDCR counter. • The TDCR-Čerenkov method is extended for complex decay schemes. • The interference contributed by Čerenkov photons emitted in the PMT induced by Compton scattering is corrected. [ABSTRACT FROM AUTHOR]

Pulse shape discrimination is an important handle to improve sensitivity in low background experiments. A dedicated setup was built to investigate the response of high-purity germanium detectors to single Compton scattered events. Using properly collimated γ -ray sources, it is possible to select events with known interaction location. The aim is to correlate the position dependent signal shape with geometrical and electrical properties of the detector. We report on design and performance of the setup with a first look on data. [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]

The general sourceless efficiency calibration has two major methods, Monte Carlo simulation and numerical calculation. Monte Carlo simulation as an important method to address the efficiency calibration in complex measurement systems, despite it being highly accurate, but inefficient and time-consuming. And although the numerical calculation is computationally efficient, its accuracy is highly influenced by the multiple Compton scattering of rays in sensitive body, and it is difficult to deal with complex measurement systems. To solve the above problems, this paper proposes a discrete numerical calculation combined with the graphical Boolean operations method for sourceless efficiency calibration. The method starts with a Monte Carlo simulation to obtain the rays deposition process in an infinite sensitive body and record deposition locations as a matrix; then, for different measurement systems, discrete numerical calculations are used to rapidly obtain the transmission process of rays to the sensitive body of the detector; finally, the two are combined to obtain the detection efficiency of the rays by using graphical Boolean operations. For the given two test models, the error between the measured and calculated results of 241Am, 137Cs, 60Co at 60 positions is within -3.61∼9.71%, and the error between the measured and calculated results of the soil source is within -1.27 to 4.26%, indicating that the method has high reliability in sourceless efficiency calibration. And in comparison with Monte Carlo simulations, it is found that the method has a good agreement with Monte Carlo simulation in efficiency calibration and the computational speed has been greatly improved. • A novel gamma-ray sourceless efficiency calibration method. • Solved the problem of multiple Compton scattering in the sensitive body of the detector in the numerical method. • Computational speed was greatly improved compared to Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

This study proposes a technique based on Compton scattering to estimate trabecular bone mineral density (TBMD), which is important for understanding bone strength, and hence, is pivotal for estimating the condition of the bone. Bone phantoms (a mixture of paraffin wax and bone powder) with various concentrations of bone ash were prepared to simulate the trabecular bone. These samples were exposed to primary gamma photon flux from a137Cs (222 GBq) radioisotope source one after the other, and the scattered photon flux was detected using an NaI(Tl) detector. The presence of the cortical bone (using aluminum sheets) and fat (tertiary butyl alcohol) around the trabecular bone was also studied to determine whether the TBMD measurements had been affected. The correlation between bone ash contents and the intensity of Compton scattering was high with a coefficient of 0.97. The outcomes suggest that TBMD is independent of the presence of the cortical bone and overlying fat, with a statistical uncertainty of ±0.3% in the count rate. The intensity of Compton scattering increased by only 1.5% when the thickness of the aluminum sheet (simulating the cortical bone) becomes was increased by four times, and by less than 5% when the bone phantom was surrounded by tertiary butyl alcohol. • We Estimate the trabecular bone mineral density (TBMD). • The bone phantoms (a mixture of paraffin wax and bone powder) were used to simulate the trabecular bone. • The cortical bone (simulated using aluminium sheets) and fat (tertiary butyl alcohol) surround the trabecular bone. • The Compton scattering technique, using gamma photon flux from 137Cs (6 Ci) as radioisotope source, was applied. [ABSTRACT FROM AUTHOR]

In this study, seven alloys with a nominal composition of (CuO 2) 0.5 M 0.5 (M = Fe, Co, Ni, Cu, Zn, Y, and Nb wt%) were produced via the powder mixed method. Alloys and pure metals were excited with 59.54 keV photon energy emitted from Am-241 radioactive source at 25°, 35°, 45°, 55°, 65°, 75′ and 85° scattering angles. The spectra of the coherent/Compton peaks were obtained by Si(Li) detector. First of all, chemical shift, (ΔE) peak energies, (E) asymmetry index (A s) and full width half maximum (FWHM) values were found in the Compton/Coherent scattering spectra obtained depending on the scattering angle and the chemical environment of the transition metals. Then the ratios of the Coherent/Compton scattering differential cross-section (dσ coherent /dσ Compton) were obtained experimentally. The experimental dσ coherent /dσ Compton ratios of the selected 3d-4d transition metals were found to be compatible with the data in the literature. Asymmetry and chemical shifts were observed in almost all samples, especially in Compton peaks, with increasing scattering angles. The chemical shifts of Compton and Coherent peaks of the alloys were found in the range of 1–932 eV. The experimental dσ koherent /dσ Compton ratios for the alloys obtained by adding Fe, Co, Ni, Cu, Zn, Y, and Nb to Cu 2 O were found as 0.697, 0.689 0.678, 0.698, 0.736, 0.755, 0.798, 0.835 at 45° scattering angle, respectively. It has been determined that the experimental dσ coherent /dσ Compton ratio for each alloy increases with increasing atomic number, while it decreases with increasing scattering angle. • (CuO 2) 0.5 M 0.5 (M = Fe, Co, Ni, Cu, Zn, Y, and Nb wt%) alloys were prepared via the powder mixed method. • Compton/Coherent scattering spectra were investigated depending on the scattering angle and chemical environment. • As, FWHM, E and ΔE parameters of the Compton/Coherent peak changed depending on the scattering angle. • As the atomic number of the metal added to the alloys increased, the dσ coherent /dσ Compton ratio enhanced. • The dσ coherent /dσ Compton ratio decreased with increasing scattering angle. [ABSTRACT FROM AUTHOR]

This paper considers the effect of pair production on the precision of D-T controllable neutron source density logging. Firstly, the principle of the traditional density logging and pulsed neutron density logging are analyzed and then gamma ray cross sections as a function of energy for various minerals are compared. In addition, the advantageous areas of Compton scattering and pair production interactions on high-energy gamma ray pulse height spectrum and the errors of a controllable source density measurement are studied using a Monte Carlo simulation method. The results indicate that density logging mainly utilizes the Compton scattering of gamma rays, while the attenuation of neutron induced gamma rays and the precision of neutron gamma density measurements are affected by pair production interactions, particularly in the gamma rays with energy higher than 2 MeV. By selecting 0.2−2 MeV energy range and performing proper lithology correction, the effect of pair production can be eliminated effectively and the density measurement error can be rendered close to the precision of chemical source density logging. [ABSTRACT FROM AUTHOR]

This article focuses on the possible application of a 137 Cs low-radioactive source (5 mCi) and a NaI(Tl) detector for measuring the saturation thickness of solid cylindrical steel targets. In order to increase the reliability of the obtained experimental results and to verify the detector response function of Compton scattering spectrum, simulation using Monte Carlo N-particle (MCNP5) code is performed. The obtained results are in good agreement with the response functions of the simulation scattering and experimental scattering spectra. On the basis of such spectra, the saturation depth of a steel cylinder is determined by experiment and simulation at about 27 mm using gamma energy of 662 keV ( 137 Cs) at a scattering angle of 120°. This study aims at measuring the diameter of solid cylindrical objects by gamma-scattering technique. [ABSTRACT FROM AUTHOR]

Examination of physical interactions of photons in materials is a significant subject for buildup factor studies. In most of the buildup calculations, by default, coherent (Rayleigh) scattering is ignored and the Compton scattering is modeled by free-electron Klein–Nishina formula with “simple physics” treatment. In this work, photon buildup factors are calculated for many different cases including “detailed physics” by taking into account coherent and bound-electron Compton scatterings with the Monte Carlo code, MCNP5, and the results are compared with the literature values. They are computed for point isotropic photon sources up to depths of 20 mean free paths and at the three photon energies most widely used (0.06, 0.6 and 6 MeV). Calculations are made for both finite and infinite homogeneous ordinary water media. It is concluded that Coherent scattering is very dominant at low energies and for deep penetrations and assumed physical approximation (simple/detailed, finite/infinite) is the critical point for determining shielding material dimensions. After all, it can be stated that all parametric assumptions should be clearly given and indicated in the tabulation of photon buildup factors. [ABSTRACT FROM AUTHOR]

This paper presents a model to predict mass attenuation and mass energy absorption coefficients of the elements for photons of energy from 1 keV to 20 MeV. The Compton scattering component is modeled by the attenuation and energy absorption of hydrogen at photon energies above 10 keV. Photoelectric attenuation and absorption is modeled as a simple power law of photon energy, modified by a simple function of the difference between the photon energy and the K shell binding energy of the absorber atoms. Attenuation and absorption by pair production above 1.022 MeV is modeled as a quadratic function of the square root of the photon energy. The mass attenuation and mass energy absorption coefficients of compounds can be predicted by the mixture rule. The errors in the model are greatest at the lowest photon energies, in part due to a lack of experimental data for photon energies below 1 keV. Worked examples are presented for the attenuation of photons at various energies in several elements and also in water over the whole range of photon energies. [ABSTRACT FROM AUTHOR]

A method was proposed for determination mass absorption coefficient of gamma rays for compounds, alloys and mixtures. It is based on simulating interaction processes of gamma rays with target elements having atomic numbers from Z =1 to Z =92 using the MCSHAPE software. Intensities of Compton scattered gamma rays at saturation thicknesses and at a scattering angle of 90° were calculated for incident gamma rays of different energies. The obtained results showed that the intensity of Compton scattered gamma rays at saturations and mass absorption coefficients can be described by mathematical formulas. These were used to determine mass absorption coefficients for compound, alloys and mixtures with the knowledge of their Compton scattered intensities. The method was tested by calculating mass absorption coefficients for some compounds, alloys and mixtures. There is a good agreement between obtained results and calculated ones using WinXom software. The advantages and limitations of the method were discussed. [ABSTRACT FROM AUTHOR]

Abstract: Mechanical collimation with photon absorption and electronic collimation using Compton scattering are combined to form a cubic gamma camera with an active collimator. The collimator is made active by constructing it with a uniformly redundant array of patterned Bi4Ge3O12 (BGO) scintillators, which not only attenuates incident radiations but also detects scattered radiation, in a gamma-camera consisting of and five planar CsI(Na) scintillators. The entire module forms a cubic structure that generates images on the basis of radiation interactions from every direction. The coverage angle for detecting scattered radiation is 2π with a detection efficiency approximately 17 times higher than previous systems that comprised only one pair of detectors. [Copyright &y& Elsevier]

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]

Abstract: In this study, different aspects of the Compton scattering inside volume sources are illustrated using experimental approach and Monte Carlo simulation. For the low-energy range (below 100keV) scattered events represents around 30% of the whole spectrum. Influence of the source-detector geometry is discussed. The scattering effects induce strong differences in spectrum shape for different geometrical conditions. This should influence efficiency transfer factors. A new approach is proposed, including the scattered events, to avoid complex peak area determination. [Copyright &y& Elsevier]

Abstract: Nowadays the Compton scattering is widely applied in various fields. In the present paper, we explore the Compton scattering effects on the binary powder mixture scatterers. By using the Compton scattering theory, we obtain an approximate linear relationship between the scattered photon counts and the contents of the binary powder mixture scatterer. This relationship has been confirmed by conducting the Compton scattering experiments of the binary powder mixture series such as the Fe–C, Fe–Cu and Ni–Cu scatterers. Moreover, we make a discussion on the experimental errors. The Compton scattering method is helpful for measuring the contents of the binary powder mixtures. [Copyright &y& Elsevier]

Abstract: In this work we measured X-ray scatter spectra from normal and neoplastic breast tissues using photon energy of 17.44keV and a scattering angle of 90°, in order to study the shape (FWHM) of the Compton peaks. The obtained results for FWHM were discussed in terms of composition and histological characteristics of each tissue type. The statistical analysis shows that the distribution of FWHM of normal adipose breast tissue clearly differs from all other investigated tissues. Comparison between experimental values of FWHM and effective atomic number revealed a strong correlation between them, showing that the FWHM values can be used to provide information about elemental composition of the tissues. [Copyright &y& Elsevier]

Abstract: Electron densities of 33 samples of normal (adipose and fibroglangular) and neoplastic (benign and malignant) human breast tissues were determined through Compton scattering data using a monochromatic synchrotron radiation source and an energy dispersive detector. The area of Compton peaks was used to determine the electron densities of the samples. Adipose tissue exhibits the lowest values of electron density whereas malignant tissue the highest. The relationship with their histology was discussed. Comparison with previous results showed differences smaller than 4%. [Copyright &y& Elsevier]

Abstract: An inverse technique has been designed to unfold the x-ray tube spectrum from the measurement of the photons scattered by a target interposed in the path of the beam. A special strategy is necessary to circumvent the ill-conditioning of the forward transport algebraic problem. The proposed method is based on the calculation of both, the forward and adjoint analytical solutions of the Boltzmann transport equation. After testing the method with numerical simulations, a simple prototype built at the Operational Unit of Health Physics of the University of Bologna was used to test the method experimentally. The reconstructed spectrum was validated by comparison with a straightforward measurement of the X-ray beam. The influence of the detector was corrected in both cases using standard unfolding techniques. The method is capable to accurately characterize the intensity distribution of an X-ray tube spectrum, even at low energies where other methods fail. [Copyright &y& Elsevier]

Abstract: Isotropic Compton profile of NbB2 using 20 Ci 137Cs Compton spectrometer is compared with our theoretical profiles obtained from the density functional theory (DFT) within the first and the second order generalized gradient approximation (GGA) and the hybridization of Hartree–Fock and DFT. A good agreement between GGA based profiles and the experiment validates the applicability of second order GGA in momentum densities. Energy bands, density of states and real space analysis of the experimental profile show metallic character of NbB2. [Copyright &y& Elsevier]

Abstract: An X-ray scattering method is presented for determining the thickness of an organic film placed on a steel substrate. The strong peaks of characteristic X-rays are taken as an advantage to measure the intensity of backscattered photons. It is shown that the intensity of Compton scattering of characteristic X-rays is proportional to film thickness, up to the thickness of 250μm of acrylic adhesive layers. In addition, the measurement time was 300ms, providing a simple and convenient method for on-line for thickness monitoring. [Copyright &y& Elsevier]

Abstract: We present the experimental Compton profiles of TiC and TiN using 661.65keV γ-ray from 20Ci 137Cs source. To explain our experimental data on momentum densities, we have computed the theoretical profiles, energy bands and density of states using linear combination of atomic orbitals scheme within the framework of density functional theory. In addition the energy bands, density of states and Fermi surfaces using full potential linearised augmented plane wave method have also been computed. Energy bands and density of states obtained from both the theoretical models show metallic character of TiC and TiN. The anisotropies in Compton line shapes and the Fermi surface topology are discussed in term of energy bands. [Copyright &y& Elsevier]

Abstract: A scanner system, operating in a non-destructive and non-invasive way, is presented for pipeline to determine its location in land soil, wall thickness, type of liquid flowing and crack/blockage position. The present experiment simulates a real case where pipe corrosion (wall thinning) under insulation can be known from the study of incoherent scattering of 662keV gamma photons. The incoherent scattered intensity, obtained by unfolding (deconvolution) the experimental pulse-height distribution of NaI(Tl) scintillation detector with the help of inverse response matrix, provides the desired information. The method is quite sensitive for small change (∼1mm) in the thickness of pipe wall, locating a defect of 1mm width under insulation and a small change (∼0.1gmcm−3) in the density of liquid flowing through pipe. [Copyright &y& Elsevier]

Abstract: In this paper, we present the first-ever experimental Compton line shapes of HgBr2 and HgI2 using 137Cs Compton spectrometer. To compare our experimental momentum densities, we have computed the Compton profiles using Hartree–Fock and density functional theory within linear combination of atomic orbitals. We have also computed the energy bands and density of states using the linear combination of atomic orbitals and full potential linearized augmented plane wave method. On the basis of equal-valence-electron-density profiles, it is seen that HgI2 is more covalent than HgBr2 which is in agreement with the valence charge densities. The experimental isotropic profiles are found to be relatively in better agreement with the Hartree–Fock data. We have also discussed the photoluminescence and detection properties of both the halides. [Copyright &y& Elsevier]

Abstract: We present the electron momentum densities of PbCl2 and PbBr2 using 661.65keV γ-rays from 20 Ci 137Cs source. To supplement our experimental investigations, we also report energy bands, density of states, Mulliken''s population and Compton profiles of PbCl2 and PbBr2 using linear combination of atomic orbitals within Hartree–Fock and density functional theories. The energy bands are also computed employing full potential linearized augmented plane wave (FP-LAPW) method. Compton profiles are also analyzed in terms of equal-valence-electron-density scale. It shows that PbCl2 is more covalent than PbBr2, which is in agreement with the Mulliken''s population analysis. It is seen that the Hartree–Fock and density functional theory based Compton line shapes show similar type of deviations from the experimental data. The luminescence properties of these halides are explained on the basis of energy band and density of states. [Copyright &y& Elsevier]

Abstract: This paper reports results from a prototype Compton imager (PCI) which consists of three planes of silicon pixel detectors as a scattering detector followed by an array of CsI(Tl) crystals as an absorbing detector. The CsI(Tl) array is mounted directly behind the silicon detectors. Simple back-projection algorithms are not sufficient to resolve extended shapes, but iterative algorithms provide the necessary de-convolution. List-mode maximum likelihood expectation maximization (LM-MLEM) is an iterative algorithm that reconstructs the most probable source distribution for a given data set. LM-MLEM attempts to reconstruct an image by finding successive approximations to the true source data. Each data set imaged is different, but the number of iterations required for convergence is typically 10–30 for the PCI. In this paper, reconstructed images of point and extended sources using measured PCI data are presented. Data are corroborated using GEANT4 simulations. [Copyright &y& Elsevier]

Abstract: Compton imaging is used to predict the location of gamma-emitting radiation sources. The X and Y coordinates of the source can be obtained using a back-projected image and a two-dimensional peak-finding algorithm. The emphasis of this work is to estimate the source-to-detector distance (Z). The algorithm presented uses the solid angle subtended by the reconstructed image at various source-to-detector distances. This algorithm was validated using both measured data from the prototype Compton imager (PCI) constructed at the Los Alamos National Laboratory and simulated data of the same imager. Results show this method can be applied successfully to estimate Z, and it provides a way of determining Z without prior knowledge of the source location. This method is faster than the methods that employ maximum likelihood method because it is based on simple back projections of Compton scatter data. [Copyright &y& Elsevier]

Abstract: The photon-scattering effect was studied in the low-energy range 15–80keV with planar and coaxial germanium detectors. Different experimental tests have been conducted with a point source, progressively reducing the matter around the radioactive deposit, to investigate the origin and characteristics of the different spectrum components due to scattered photons (bumps). These tests were completed by Monte Carlo simulations. Finally, a peak-shape calibration was performed using several radionuclides (109Cd, 241Am, 133Ba, 137Cs and 152Eu). This allowed in identifying the main contributions to the bumps and improving the spectra processing. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to examine the potential of using scatter information to evaluate tissue density at selected sites. A method for non-invasively generating profiles of density distribution within an object using Compton scattered X-rays is presented. The Compton scatter method is modified to scan longitudinal sections of composite phantoms and samples of tissue substitute materials. Line scan data are used to describe how the detected count rate changes in response to localized density variations within an extended object. The physical limitations of quantification are discussed, including the effect of attenuation, multiple scatter, and limited spatial resolution. Further, the theory of the method, its performance and results of experimental phantom studies are described. The results presented indicate that the suggested method has the potential for measuring physical density distribution within an object with a spatial resolution of 2mm and an accuracy of approximately 4% under the circumstances in which attenuation correction is avoided. [Copyright &y& Elsevier]

Density is one of the indicators that can be utilized to distinguish an explosive material from an innocuous anomaly. Compton scattering of photons can be used to provide such density indication. Although X-rays have been employed for this purpose, isotopic gamma-rays offer some advantage for use in a portable device, because of their small size and self-powered nature. Radioisotopes were considered in the 1970''s by the US Army. This work re-examines the utility of these sources for the detection of shallowly buried anti-personnel landmines. Monte Carlo studies indicated that the most effective configuration for identifying and locating a buried landmine should employ a collimated 241Am source, along with a set of well-collimated detectors. Experimental measurements verified the feasibility of the proposed method and demonstrated the detectablility of mockups of landmines as small as 45 mm in diameter buried near the soil surface, or mockups larger than 80 mm in diameter buried at a depth of 80 mm, in light soil. In heavy soil, targets 80 mm in diameter were detectable at a depth of 30 mm. The use of the low-energy (60 keV) 241Am source makes it possible to design a light-weight hand-held device that can augment other methods of detecting plastic landmines. [Copyright &y& Elsevier]

A non-rotating method for non-intrusively determining the electron density at a point embedded within an object, without full imaging, is presented. Advantage was taken of the multienergetic nature of X-ray photons to devise a dual energy-group multiple-detector scattering scheme for density determination. A measurement model that relates the density of the object to the detector response was formulated, then inverted to determine the electron density at the monitored point. Normalization factors were calculated to compensate for the wide energy distribution of the X-ray photons, and account for other system parameters. In addition, the spread in the source and detectors fields-of-view was accommodated by calculating in advance the volume of the inspection voxel. The method was experimentally applied to a variety of geometries and materials, showing that the electron density can be calculated with a reasonable uncertainty. [Copyright &y& Elsevier]

In this study, we measured the effective atomic numbers of some boron compounds (H 4 BNa, H 3 BO 3 , Na 2 B 4 O 17 H 20 , B 4 C, BN, NaCaB 5 O 17 H 16 , B 2 O 3 , Ca 2 B 6 O 16 H 10 , Zn 2 B 6 O 14 H 6 , TiB 2 , Fe 2 B, Ni 3 B, ZrB 2 , and LaBO 3) by using 59.54 keV energy gamma rays emitted from an Am-241 radioactive source. Rayleigh and Compton scattering peaks were detected using a high purity germanium detector with a resolution of 182 eV at 5.9 keV. In addition, the effective atomic numbers of the boron compounds were theoretically calculated by using WinXCOM code. We concluded that the calibration curve obtained can be used for the qualitative analysis of compounds with effective atomic numbers in the range of 3.95 ≤ Z ≤ 54.15 because the experimental and theoretical effective atomic numbers were in very good agreement. [ABSTRACT FROM AUTHOR]

Airborne radionuclide monitoring is considered to be the most certain way to detect a clandestine nuclear weapon test. The activity concentration of radioxenon samples collected by the radionuclide stations of the International Monitoring System (IMS) for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) is generally performed at the low-level, hence it is necessary to improve the detection sensitivity of the radioactivity measuring apparatus for radionuclide monitoring. The Compton-suppressed spectrometer (CSS) has the advantage of reducing the background and improving the sensitivity in the environmental level measurement. Therefore, the measurement of the relevant radioxenon sample at the environmental level is feasible by using CSS. To assess the performance of CSS for radioxenon measurements, the Compton-suppressed and unsuppressed spectra of the 133Xe and 127Xe samples have been acquired, and subsequently, the information of the full energy peaks (FEP) in the spectra were compared. The assessment indicates that CSS can provide high sensitivity, simple operation, and straightforward activity determination, and it can be regarded as an appropriate apparatus in the radioxenon measurement. • 133Xe and 127Xe samples were measured using Compton-suppressed spectrometer. • Full energy peaks of radioxenon isotopes were more prominent in Compton-suppressed spectrum. • The sensitivity to the radioxenon measurement was assessed for Compton-suppressed spectrum. [ABSTRACT FROM AUTHOR]

Photon-induced nuclear excitation (i.e. photo-excitation) can be used for production of nuclear isomers, which have potential applications in astrophysics, energy storage, medical diagnosis and treatment. This paper presents a feasibility study on photo-excitation production of four nuclear isomers (103mRh, 113m,115mIn and 176mLu) with intense γ-ray source based on laser-electron Compton scattering (LCS). The decay properties of these isomers and their potential applications in medical diagnosis and treatment were reviewed. The cross-section curve, simulated yield and activity of product of each photo-excitation process were calculated. The cutoff energy of LCS γ-ray beam was optimized by adjusting electron beam energy in order to maximize the isomer activity. It is found that the specific activity of the above-mentioned isomers can exceed ~0.2 GBq/g for 6-h target irradiation at an intensity of 1013 γ/s. Our simulation results suggest the prospect of producing medically interesting radionuclides with photo-excitation using the state-of-art LCS γ-ray beam facility. • Present a feasibility study on production of nuclear isomers using high-intensity γ-ray source based on (LCS). • The cutoff energy of LCS γ-ray beam was optimized by adjusting electron beam energy in order to maximize the isomer activity. • The specific activity of these isomers can exceed ~0.2 GBq/g for 6-h target irradiation at an intensity of 1013 γ/s. • The prospect of producing medically interesting isomers with photo-excitation using the state-of-art LCS γ-ray beam facility. [ABSTRACT FROM AUTHOR]

The newly-built Compton suppression system at the HL-2A tokamak works in a harsh fusion neutron field especially when the second neutral beam injection system is put into application. The present paper performed Geant4 simulations to study the influences of fusion neutrons on Compton suppressed γ-spectrum analyses. The simulation data show that the influence of fusion neutrons on suppressed γ-spectrum shape is limited, while the influence on detection efficiencies is considerable. Consequently, the changes of detection efficiencies caused by the coexisting neutrons must be taken into account in the subsequent γ-spectrum analyses. Hence, the empirical formulas of γ-ray detection efficiencies of the Compton suppression system, which had considered the influences of fusion neutrons, were put forward and then applied to unfold the experimental γ-spectra. This work lays a superior foundation for the further analyses of the Compton suppressed γ-spectra at the HL-2A tokamak. • Neutrons have limited influence on the Compton suppressed γ-spectra. • Geant4 calculations have considered the accidental coincidences. • Unfolded results for experimental spectra agree well with theoretical values. [ABSTRACT FROM AUTHOR]

Alloys of the type Pb 60 Sn 20 Zn x Cd (20-x) where x = 0, 5, 10, 15 or 20 were prepared by a conventional melt quench technique. The intensity distribution of backscattered photons from the radioactive isotopes 22Na and 137Cs (with photon energies of 511 keV and 662 keV, respectively) were recorded for different thicknesses of alloy samples and some metallic samples (Al, Zn, Sn and Pb) with use of a GAMMA-RAD5 spectrometer (76 mm × 76 mm NaI(Tl) scintillation detector). Backscattered photon intensities were plotted as a function of both the atomic number and the target thickness. A best fit curve was drawn between backscattered photon counts and the atomic number of the metallic samples, from which the effective atomic numbers (Z eff) of the alloys were obtained at a particular photon energy as well as thickness. The experimentally obtained Z eff values are in good agreement with the theoretical ones (based on mass attenuation coefficients from the WinXCom database). The plot of intensity versus thickness shows that the intensity of backscattered photons increases with sample thickness. The albedo factors (energy albedo, number albedo and dose albedo) were also determined experimentally at these photon energies for the alloys and metallic samples. In the Compton scattering dominant region, the albedo factors decrease with an increase in atomic number as well as with an increase in photon energy. • Alloys of the type Pb60Sn20ZnxCd(20-x) where x = 0, 5, 10, 15, 20, were prepared by melt quench technique. • Backscattered photon spectra of alloys and metals (Al, Zn, Sn, Pb) at 511 keV & 662 keV were recorded with NaI(Tl) detector. • The effective atomic number and albedo factors (energy albedo, number albedo and dose albedo) were measured experimentally. • The outcomes of the present work can be useful in efficient shield designing. [ABSTRACT FROM AUTHOR]

In this study, we validated the feasibility of an energy weighted algorithm that highlights a characteristic area including the Compton edge as a single peak in a proof-of-principle radiation portal monitor system with a plastic scintillator measuring 50 × 100 × 5 cm3. We measured the energy weighted spectra with steel shielding and the dynamic movements of the 137Cs and 60Co sources. The results showed that the peak locations of each source could be identified under shielded or dynamic motion conditions, each within a maximum difference of 0.08 MeV. • Energy weighted algorithm evaluated with spectra for 137Cs, 60Co, 226Ra, and 22Na. • Large plastic scintillator employed that measured 50 × 100 × 5 cm3. • Shielded or moving radioactive sources discriminated with energy weighted spectra. • Minimum measurement time for peak detection evaluated. [ABSTRACT FROM AUTHOR]

This paper studied the impact of the photoelectric effect of X-ray density logging in order to improve the accuracy of X-ray measurement density. Firstly, the laws governing the changes of the Compton scattering and photoelectric effect of X-rays in the formation were analyzed based on the principle of X-ray attenuation in the formation and using the XCOM program. Secondly, the impact of photoelectric effect on X-ray density logging was studied on the basis thereof. Thirdly, a method for correcting photoelectric effect by calculating the formation bulk density using the counts in both lithology window and density window was proposed. Finally, the proposed method was verified through MCNP simulation. The results indicate that photoelectric effect was an important factor affecting the accuracy of X-ray density measurement, and the lower the X-ray energy was, the greater the impact of photoelectric effect on X-ray density measurement would be and the lower the accuracy of density measurement would be. As the γ-rays released from a Cs-137 source were at a high energy level, the impact of photoelectric effect was basically negligible when the formation bulk density was calculated using the counts in density window; on the contrary, the X-rays released from the X-ray source was at a low energy level, the impact of photoelectric effect could not be neglected when the formation bulk density was measured using X-ray. The method for calculating the formation bulk density proposed in this paper can effectively eliminate the impact of photoelectric effect and reach up to a measurement accuracy level of about 0.01g/cm3, providing a theoretical foundation for accurate density measurement during X-ray density logging. • The effect of photoelectric effect on X-ray measurement density is verified. • The smaller the X-ray energy, the greater the impact of the photoelectric effect. • The photoelectric effect can be corrected by the method of combining the density energy window lithology energy window. [ABSTRACT FROM AUTHOR]

We develop a compact, high signal-to-noise ratio line-detector array Compton scatter imaging system based on Y 2 SiO 5 scintillators and silicon photomultipliers. It is shown that the system's response uniformity is better than 98% for low-Z eff materials after a specific correction. Backscatter images of an "IHEP"-character model, cubes of different materials, and some other applications are presented, to show its potential for use in nondestructive testing. • A line-detector array based on SiPMs and YSO was developed. • Scintillation light loss and optical crosstalk were reduced. • Detector was applied to a Compton scatter imaging system. • A specific system response-uniformity correction was applied and discussed. • Backscatter images were presented to show its potential in NDT applications. [ABSTRACT FROM AUTHOR]

In this study, the performance of a Compton Single Photon Emission Computed Tomography (SPECT) imager when in vivo monitoring the position and distribution of 225Ac radionuclide in targeted alpha therapy (TAT) was evaluated. When 225Ac radionuclide, which emits various γ-rays (218 and 440 keV), is used in TAT, both the photoelectric and Compton scattering events can be used for image reconstruction. Moreover, all information pertaining to the various γ-rays of the 225Ac radionuclide can be individually or simultaneously utilized in the reconstructed image. Three types of simulation phantoms and a quantitative evaluation method were used to compare the performance of the Compton SPECT imager to that of conventional SPECT imaging, which uses only photoelectric events, and the results demonstrated that the Compton SPECT imager exhibited a higher performance as the effective count for the image reconstruction was higher. To verify the accuracy of the position and distribution of the 225Ac radionuclide that had been inserted into the phantom, reconstructed images of the various γ-rays were combined with cross-sectional images of the human phantom and all combined images were found to match the predetermined simulation conditions. In conclusion, the simulation results demonstrated the feasibility of the in vivo monitoring of the position and distribution of 225Ac radionuclide using the γ-rays in TAT. • The performance of a Compton SPECT imager for 225Ac in TAT was evaluated. • The in vivo monitoring of the position and distribution of 225Ac was discussed. • A Monte Carlo simulation based phantom study was applied in this research. [ABSTRACT FROM AUTHOR]