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A method to fit Compton profiles in x‐ray fluorescence (XRF) spectroscopy using a line shape calculated from first principles is proposed. The fitting procedure incorporates the Compton profile calculations and the double Compton scattering line shape algorithm. The results demonstrate the effectiveness of the fitting approach in accurately describing the measured scattering spectra, with good agreement observed between the fit and experimental data. The findings of this study can be used for more accurate characterization of the scattering peaks in XRF spectroscopy. [ABSTRACT FROM AUTHOR]

Understanding the correlation between chemical and microstructural properties is critical for unraveling the fundamental relationship between materials chemistry and physical structures that can benefit materials science and engineering. Here, we demonstrate novel in situ correlative imaging of the X‐ray Compton scattering computed tomography (XCS‐CT) technique for studying this fundamental relationship. XCS‐CT can image light elements that do not usually exhibit strong signals using other X‐ray characterization techniques. This paper describes the XCS‐CT setup and data analysis method for calculating the valence electron momentum density and lithium‐ion concentration, and provides two examples of spatially and temporally resolved chemical properties inside batteries in 3D. XCS‐CT was applied to study two types of rechargeable lithium batteries in standard coin cell casings: (1) a lithium‐ion battery containing a cathode of bespoke microstructure and liquid electrolyte, and (2) a solid‐state battery containing a solid‐polymer electrolyte. The XCS‐CT technique is beneficial to a wide variety of materials and systems to map chemical composition changes in 3D structures. [ABSTRACT FROM AUTHOR]

Objective: To assess the impact of scatter radiation on quantitative performance of first and second‐generation dual‐layer spectral computed tomography (DLCT) systems. Method: A phantom with two iodine inserts (1 and 2 mg/mL) configured to intentionally introduce high scattering conditions was scanned with a first‐ and second‐generation DLCT. Collimation widths (maximum of 4 cm for first generation and 8 cm for second generation) and radiation dose levels were varied. To evaluate the performance of both systems, the mean CT numbers of virtual monoenergetic images (MonoEs) at different energies were calculated and compared to expected values. MonoEs at 50 versus 150 keV were plotted to assess material characterization of both DLCTs. Additionally, iodine concentrations were determined, plotted, and compared against expected values. For each experimental scenario, absolute errors were reported. Results: An experimental setup, including a phantom design, was successfully implemented to simulate high scatter radiation imaging conditions. Both CT scanners illustrated high spectral accuracy for small collimation widths (1 and 2 cm). With increased collimation (4 cm), the second‐generation DLCT outperformed the earlier DLCT system. Further, the spectral performance of the second‐generation DLCT at an 8 cm collimation width was comparable to a 4 cm collimation on the first‐generation DLCT. A comparison of the absolute errors between both systems at lower energy MonoEs illustrates that, for the same acquisition parameters, the second‐generation DLCT generated results with decreased errors. Similarly, the maximum error in iodine quantification was less with second‐generation DLCT (0.45 and 0.33 mg/mL for the first and second‐generation DLCT, respectively). Conclusion: The implementation of a two‐dimensional anti‐scatter grid in the second‐generation DLCT improves the spectral quantification performance. In the clinical routine, this improvement may enable additional clinical benefits, for example, in lung imaging. [ABSTRACT FROM AUTHOR]

Recent advances in quantum crystallography have shown that, beyond conventional charge density refinement, a one‐electron reduced density matrix (1‐RDM) satisfying N‐representability conditions can be reconstructed using jointly experimental X‐ray structure factors and directional Compton profiles (DCP) through semidefinite programming. So far, such reconstruction methods for 1‐RDM, not constrained to idempotency, have been tested only on a toy model system (CO2). In this work, a new method is assessed on crystalline urea [CO(NH2)2] using static (0 K) and dynamic (50 K) artificial experimental data. An improved model, including symmetry constraints and frozen core‐electron contribution, is introduced to better handle the increasing system complexity. Reconstructed 1‐RDMs, deformation densities and DCP anisotropy are analysed, and it is demonstrated that the changes in the model significantly improve the reconstruction quality, even when there is insufficient information and data corruption. The robustness of the model and the strategy are thus shown to be well adapted to address the reconstruction problem from actual experimental scattering data. [ABSTRACT FROM AUTHOR]

Background: Silicon (Si) is a possible sensor material for photon counting detectors (PCDs). A major drawback of Si is that roughly two‐thirds of x‐ray interactions in the diagnostic energy range are Compton scattering. Because Compton scattering is an energy‐insensitive process, it is commonly assumed that Compton events retain little spectral information. Purpose: To quantify how much information can be recovered from Compton scattering events in models of Si PCDs. Methods: We built a simplified model of Si interactions including two interaction mechanisms: photoelectric effect and Compton scattering. We considered three different binning options that represent strategies for handling Compton events: in Compton censoring, all events under 38 keV (the maximum energy possible from Compton scattering for a 120 keV incident photon) were discarded; in Compton counting, all events between 1 and 38 keV were placed into a single bin; in Compton binning, all events were placed into energy bins of uniform width. These were compared to the ideal detector, which always recorded the correct energy (i.e., 100% photoelectric effect). Every photon was assumed to interact once and only once with Si, and the energy bin width was 5 keV. In the primary analysis, the Si detector was irradiated with a 120 kV spectrum filtered by 30 cm of water, with 99.5% of the arriving spectrum above 38 keV so that there was good separation between photoelectric effect and Compton scattering, and the figures of merit were the Cramér–Rao lower bound (CRLB) of the variance of iodine and water basis material decomposition images, as well as the CRLB of virtual monoenergetic images (i.e., linear combinations of material images) that maximize iodine CNR or water CNR. We also constructed a local linear estimator that attains the CRLB. In secondary analyses, we applied other sources of spectral distortion: (1) a nonzero minimum energy threshold; (2) coarser, 10 keV energy bins; and (3) a model of charge sharing. Results: With our chosen spectrum, 67% of the interactions were Compton scattering. Consistent with this, the material decomposition variance for the Compton censoring model, averaged over both basis materials, was 258% greater than the ideal detector. If Compton events carried no spectral information, the Compton counting model would show similar variance. Instead, its basis material variance was 103% greater than the ideal detector, implying that Compton counts indeed carry significant spectral information. The Compton binning model had a basis material variance 60% greater than the ideal detector. The Compton binning model was not affected by a 5 keV minimum energy threshold, but the variance increased from 60% to 107% when charge sharing was included and to 78% with coarser energy bins. For optimized CNR images, the average variance was 149%, 12%, and 10% higher than the ideal detector for the Compton censoring, counting, and binning models, reinforcing the hypothesis that Compton counts are useful for detection tasks and that precise energy assignments are not necessary. Conclusions: Substantial spectral information remains after Compton scattering events in silicon PCDs. [ABSTRACT FROM AUTHOR]

This paper presents an electromagnetic analysis of a moving infinitely long line source illuminating an infinitely long metallic wire at rest. The study uses the full‐wave numerical finite difference time domain (FDTD) method, which is based on the spatial and temporal discretization of Maxwell's equations. Movement is computed within the FDTD technique by varying the position of the line source at each time loop. An analogy is proposed between the wavelength spectrum of the simulated electromagnetic field and the Compton scattering experiment. A good agreement is obtained between theoretical analysis, numerical results, and Compton experimental data. [ABSTRACT FROM AUTHOR]

E. Williams et al. (2022, commented paper) questioned electron energy spectra derived from thunderstorm ground enhancements (TGEs) measured on Aragats; they concluded that "A more likely origin for any detected electrons at 3.2 km above sea level is Compton scattering and pair production activated by longer‐range bremsstrahlung gamma rays, themselves produced by runaway electron encounters with nuclei in the breakeven field at higher altitude." In this comment, we show that the selection criteria of "electron" TGEs unambiguously reject the assumption of the origination of TGE electrons measured on Aragats from the Compton and pair production processes. Thus, the strong accelerating electric field above the earth's surface can be significantly lower (25–150 m) than derived in the commented paper 500 m altitude. Plain Language Summary: Electron accelerators operate in the thunderous atmosphere, sending copious particles to the Earth's surface. To get inside the models of electron acceleration and multiplication by strong atmospheric fields, the critical problem is the measurement of electrons and their energies as they arrive at the earth's surface. It is rather tricky because electrons are fast attenuated in the air, and the flux of accompanied gamma rays is attenuated much less and reaches the ground in overwhelming amounts. We developed special hardware and software methods to prove electrons' existence in the vast particle fluxes reaching the ground and to measure their energies. Simulations and careful examination of the registered particle fluxes check these methods. Key Points: The contribution of the Compton scattered and pair‐production electrons to TGE flux is negligible and cannot "mimic" the TGE electron fluxThe criteria used in the energy spectrum recovery from Aragats Solar Neutron Telescope (ASNT) reliably select "electron" TGE events and reject TGE events with small electron contentIf the strong accelerating electric field terminates low above the earth's surface (25–100 m), electrons from the large RREAs reach ASNT, and their energy spectrum can be reliably recovered [ABSTRACT FROM AUTHOR]

X‐ray atomic pair distribution function (XPDF) measurements using a two‐dimensional area detector have been of great value in studying atomic structures of materials with varying degrees of disorder. However, an area detector does not have energy resolution. Thus, incoherent inelastic Compton scattering and fluorescence are not discriminated, contaminating coherent elastic scattering. This paper investigates the effects of random noise from incoherent scattering on XPDF analysis. To conduct the study, the elastic scattering, Compton scattering and fluorescence of In0.33Ga0.67As alloy were separately measured using an intrinsic Ge solid‐state detector with energy resolution. It is found that the addition of Compton scattering with a noise‐to‐signal ratio of about 0.8% results in the smearing of diffuse scattering in the high‐Q region. Moreover, adding extra noise from fluorescence increases the smearing, overwhelming the diffuse scattering. Additionally, simulated data of elastic and Compton scattering on ferroelectric Ba(Ti0.8Zr0.2)O3 were used to investigate the evolution of noise fluctuation and its effects on the XPDF as a function of total intensity. [ABSTRACT FROM AUTHOR]

Background: Accurate dose computation is critical in precision small animal radiotherapy. The Monte Carlo simulation method is the gold standard for radiation dose computation but has not been widely implemented in practice due to its low computation efficiency. Purpose: This study aims to develop a GPU‐accelerated radiation dose engine (GARDEN) based on the Monte Carlo simulation method for fast and accurate dose computation. Methods: In the GARDEN simulation, Compton scattering, Rayleigh scattering, and photoelectric effect were considered. The Woodcock tracking algorithm and GPU‐specific acceleration techniques were used to obtain a high computational efficiency. Benchmark studies against both Geant4 simulations and experimental measurements were performed for various phantoms and beams. Finally, a conformal arc treatment plan was designed for a lung tumor to further evaluate the accuracy and efficiency in small animal radiotherapy. Result: The engine attained a speed‐up of 1232 times in a homogeneous water phantom and 935 times in a water‐bone‐lung heterogeneous phantom when compared with Geant4. Both the depth‐dose curves and cross‐sectional dose profiles for various radiation field sizes showed a great match between measurements and the GARDEN calculations. For in vivo dose validation, the differences between calculations and measurements in the mouse thorax and abdomen were 2.50% ± 1.50% and 1.56% ± 1.40%, respectively. The computation time for an arc treatment plan delivered from 36 angles was 2 s at a <1% uncertainty level using an NVIDIA GeForce RTX 2060 SUPER GPU. When compared with Geant4, the 3D gamma comparison passing rate was 98.7% at 2%/0.3 mm criteria. Conclusion: GARDEN can perform fast and accurate dose computations in heterogeneous tissue environments and is expected to play a vital role in image‐guided precision small animal radiotherapy. [ABSTRACT FROM AUTHOR]

Sensitivity and detection limit of X‐ray detectors are crucial for security checks, medical diagnoses, and industrial inspections. In this study, it is reported that introducing some cations containing lone‐pair electrons is beneficial for enhancing the Compton scattering effect and thus improving X‐ray detection performance. As an example, SnTe3O8 is selected and grown as a novel high‐temperature X‐ray detection crystal. Because of the high resistivity of 2 × 1014 Ω cm and high mobility lifetime product of 3.22 × 10−4 cm2 V−1, SnTe3O8 X‐ray detector exhibits a high sensitivity of 436 µC Gyair−1 cm−2 under 120 keV hard X‐ray, a low dark current drift of 2.44 × 10−9 nA cm−1 s−1 V−1 and a record low detection limit of 8.19 nGyair s−1 among all oxide X‐ray detectors. Furthermore, the high‐temperature sensitivity of SnTe3O8 X‐ray detector is enhanced to 617 µC Gyair−1 cm−2 at 175 °C, which is ≈31 times larger than that of the commercial α‐Se. The high thermal stability and stable high‐temperature sensitivity of SnTe3O8 single crystal X‐ray detectors have potential applications in high‐temperature environments. The results not only provide an excellent high‐temperature X‐ray detection crystal but also propose an effective method to explore X‐ray detector materials with excellent performances. [ABSTRACT FROM AUTHOR]

To quickly identify maritime sites polluted by heavy metal contaminants, reductions in the size of instrumentation have made it possible to bring an X‐ray fluorescence (XRF) analyzer into the field and in direct contact with various samples. The choice of source‐sample‐detector geometry plays an important role in minimizing the Compton scattering noise and achieving a better signal‐to‐noise ratio (SNR) in XRF measurement conditions, especially for analysis of wet sediments. This paper presents the influence of geometrical factors on a prototype, designed for in situ XRF analysis of mercury (Hg) in wet sediments using a 57Co excitation source and an X‐ray spectrometer. The unique XRF penetrometer prototype has been constructed and tested for maritime wet sediment. The influence on detection efficiency and SNR of various geometrical arrangements have been investigated using the combination of Monte Carlo simulations and laboratory experiments. Instrument calibration was performed for Hg analysis by means of prepared wet sediments with the XRF prototype. The presented results show that it is possible to detect Hg by K‐shell emission, thus enabling XRF analysis for underwater sediments. Consequently, the XRF prototype has the potential to be applied as an environmental screening tool for analysis of polluted sediments with relatively high concentrations (e.g., >2880 ppm for Hg), which would benefit in situ monitoring of maritime pollution caused by heavy metals. [ABSTRACT FROM AUTHOR]

Background: Dedicated, breast‐specific positron emission tomography (BPET)–cone‐beam computed tomography (BPET/CT) systems have been developed to improve detection and diagnosis of cancer in women with indeterminate mammograms caused by radiodense breasts. The absorption of X‐rays that often vexes mammography in this subset of women does not affect the detection of the high energy annihilation photons used in PET. PET imaging of the breast, however, is subject to limitations caused by their comparatively low spatial resolution (∼2 mm) and often moderate radiotracer uptake in lesions. Purpose: The purpose of this investigation is to explore the PET‐based lesion detection capabilities of a BPET/CT scanner developed by the Department of Radiology Instrumentation group at West Virginia University. Methods: The PET component of the system consists of a rotating pair of 96 × 72 arrays of 2 × 2 × 15 mm3 LYSO scintillator elements. The cone‐beam‐CT component utilized a pulsed X‐ray source and flat panel detector operated in portrait orientation. The density maps created by the CT scanner were used to correct the BPET data for photon attenuation and Compton scattering. The nonuniform uptake of 18F‐fluorodeoxyglucose (FDG) in normal breast tissue was emulated in a specially designed phantom consisting of an acrylic cylinder filled with a mixture of acrylic beads and liquid containing FDG. FDG‐avid lesions were simulated with agar spheres (3, 4, 6, 8, and 10 mm diameters) containing vary amounts of FDG to produce target‐to‐background ratios (TBR) of 6:1, 8:1, and 10:1. The spheres also contained X‐ray contrast agent to make even the smallest ones readily visible in CT images. Positions of all the lesions were identified in the CT images. These positions were used to extract signal present and signal absent sub‐images from the PET images. The sub‐images were then input to software that calculated areas‐under‐the‐curve for two numerical model observers (Laguerre–Gauss channelized Hotelling observer and non‐prewhitening matched filter). Results: The results showed that the smallest detectable lesion with this system is no smaller than ∼3 mm in diameter with a TBR of 6:1. Simulated lesions with diameters of 4 mm and greater were calculated to have good to excellent likelihood of detection for all TBRs tested. Conclusion: The results from this investigation identified the detectability capabilities and limitations for a dedicated breast‐PET/CT scanner. Its ability to detect relatively small simulated FDG‐avid breast lesions for a range of TBRs indicates its potential for clinical application. Finally, the study used methodologies that could be applied to a detectability assessment of other PET/CT scanners. [ABSTRACT FROM AUTHOR]

This article demonstrates the feasibility of obtaining accurate pair distribution functions of thin amorphous films down to 80 nm, using modern laboratory‐based X‐ray sources. The pair distribution functions are obtained using a single diffraction scan without the requirement of additional scans of the substrate or of the air. By using a crystalline substrate combined with an oblique scattering geometry, most of the Bragg scattering of the substrate is avoided, rendering the substrate Compton scattering the primary contribution. By utilizing a discriminating energy filter, available in the latest generation of modern detectors, it is demonstrated that the Compton intensity can further be reduced to negligible levels at higher wavevector values. Scattering from the sample holder and the air is minimized by the systematic selection of pixels in the detector image based on the projected detection footprint of the sample and the use of a 3D‐printed sample holder. Finally, X‐ray optical effects in the absorption factors and the ratios between the Compton intensity of the substrate and film are taken into account by using a theoretical tool that simulates the electric field inside the film and the substrate, which aids in planning both the sample design and the measurement protocol. [ABSTRACT FROM AUTHOR]

The performance of Li+ ion batteries (LIBs) is hindered by steep Li+ ion concentration gradients in the electrodes. Although thick electrodes (≥300 µm) have the potential for reducing the proportion of inactive components inside LIBs and increasing battery energy density, the Li+ ion concentration gradient problem is exacerbated. Most understanding of Li+ ion diffusion in the electrodes is based on computational modeling because of the low atomic number (Z) of Li. There are few experimental methods to visualize Li+ ion concentration distribution of the electrode within a battery of typical configurations, for example, coin cells with stainless steel casing. Here, for the first time, an interrupted in situ correlative imaging technique is developed, combining novel, full‐field X‐ray Compton scattering imaging with X‐ray computed tomography that allows 3D pixel‐by‐pixel mapping of both Li+ stoichiometry and electrode microstructure of a LiNi0.8Mn0.1Co0.1O2 cathode to correlate the chemical and physical properties of the electrode inside a working coin cell battery. An electrode microstructure containing vertically oriented pore arrays and a density gradient is fabricated. It is shown how the designed electrode microstructure improves Li+ ion diffusivity, homogenizes Li+ ion concentration through the ultra‐thick electrode (1 mm), and improves utilization of electrode active materials. [ABSTRACT FROM AUTHOR]

Purpose: Compared to energy integration, photon‐counting x‐ray detection facilitates the spectral channelization (energy binning) in spectral CT and thus offers the opportunity to implement data acquisition via sophisticated schemes, for example, gapping or interleaving in spectral channels. In this article, we report our investigation of the performance of material decomposition based spectral imaging in photon‐counting CT implemented in such data acquisition schemes, and their comparison with the benchmark scheme and other schemes without spectral gapping or interleaving. Materials and methods: Using a deliberately designed anthropomorphic head phantom that mimics the intracranial soft tissues and bony structures, a simulation study is carried out with the focus on two‐material decomposition based spectral imaging in photon‐counting computed tomography (CT), under both ideal and realistic detector spectral responses. The projection data are acquired in four spectral channels, and then are sorted to implement the schemes of gapping ((ch1, ch3); (ch2, ch4); (ch1, ch4)) and interleaving ((ch1, ch3) + (ch2, ch4); (ch1, ch4) + (ch2, ch3); ((ch1 + ch3), (ch2 + ch4)); ((ch1 + ch4), (ch2 + ch3))) in spectral channels, in addition to the benchmark scheme ((ch1 + ch2), (ch3 + ch4)) and other conventional schemes (ch1, ch2), (ch2, ch3) and (ch3, ch4), where "ch" denotes channel, "+" denote addition, and (·,·) the operation of material decomposition and image reconstruction. Using the contrast‐to‐noise ratio between targeted regions of interest as the figure of merit, we study the performance of spectral imaging (material specific and virtual monochromatic) associated with these spectral channelization schemes. Results: Under ideal detector spectral response, the scheme (ch1, ch4) outperforms the benchmark scheme ((ch1 + ch2), (ch3 + ch4)) and others in gapped and/or interleaved spectral channelization in material specific imaging, while the interleaved scheme (ch1, ch4) + (ch2, ch3) performs the best in virtual monochromatic imaging. Notably, only about half x‐ray dose is utilized in the scheme (ch1, ch4) for image formation. Under realistic detector spectral response, the difference in imaging performance over all spectral channelization schemes diminishes, along with degradation in each scheme's individual performance. The results suggest that (i) different strategy in spectral channelization may have to be exercised in material specific imaging and virtual monochromatic imaging, respectively, and (ii) the spectral distortion in realistic detector's response due to charge‐sharing, Compton scattering, and fluorescent escaping should be mitigated as much as possible. Conclusion: The spectral channelization schemes and associated imaging performance reported herein are novel and thus informative to the community, which may further the understanding of physical fundamentals and design principles for material decomposition based spectral imaging in photon‐counting CT and other x‐ray related imaging modalities. [ABSTRACT FROM AUTHOR]

The Gamma Factory (GF) is an ambitious proposal, currently explored within the CERN Physics Beyond Colliders program, for a source of photons with energies up to ≈400 MeV and photon fluxes (up to ≈1017 photons s−1) exceeding those of the currently available gamma sources by orders of magnitude. The high‐energy (secondary) photons are produced via resonant scattering of the primary laser photons by highly relativistic partially‐stripped ions circulating in the accelerator. The secondary photons are emitted in a narrow cone and the energy of the beam can be monochromatized, down to 10−3–10−6 level, via collimation, at the expense of the photon flux. This paper surveys the new opportunities that may be afforded by the GF in nuclear physics and related fields. [ABSTRACT FROM AUTHOR]

For photon energies from several 10 keV up to a few MeV Compton polarimetry is an indispensable tool to gain insight into subtle details of fundamental atomic radiative processes. Within the SPARC collaboration several segmented semiconductor detectors are developed that are well suited for application as efficient Compton polarimeters. In this report, these recent developments are reviewed and it is discussed how Compton polarimetry can be employed at the upcoming Gamma Factory. [ABSTRACT FROM AUTHOR]

X‐ray spectra scattered at 90° by acrylic resin plates of various thicknesses are measured. The intensity and polarization of Compton‐scattered X‐rays are estimated from the spectra. As the thickness of the slab increases, the intensity increases but the polarization decreases. The optimal thickness for a polarized X‐ray fluorescence spectrometer is determined, which provides both high intensity and high polarization. [ABSTRACT FROM AUTHOR]

This article retraces different methods that have been explored to account for the atomic thermal motion in the reconstruction of one‐electron reduced density matrices from experimental X‐ray structure factors (XSF) and directional Compton profiles (DCP). Attention has been paid to propose the simplest possible model, which obeys the necessary N‐representability conditions, while accurately reproducing all available experimental data. The deconvolution of thermal effects makes it possible to obtain an experimental static density matrix, which can directly be compared with theoretical 1‐RDM (reduced density matrix). It is found that above a 1% statistical noise level, the role played by Compton scattering data becomes negligible and no accurate 1‐RDM is reachable. Since no thermal 1‐RDM is available as a reference, the quality of an experimentally derived temperature‐dependent matrix is difficult to assess. However, the accuracy of the obtained static 1‐RDM, through the performance of the refined observables, is strong evidence that the Semi‐Definite Programming method is robust and well adapted to the reconstruction of an experimental dynamical 1‐RDM. [ABSTRACT FROM AUTHOR]

A feasible implementation of a novel X‐ray detector for highly energetic X‐ray photons with a large solid angle coverage, optimal for the detection of Compton X‐ray scattered photons, is described. The device consists of a 20 cm‐thick sensitive volume filled with xenon at atmospheric pressure. When the Compton‐scattered photons interact with the xenon, the released photoelectrons create clouds of secondary ionization, which are imaged using the electroluminescence produced in a custom‐made multi‐hole acrylic structure. Photon‐by‐photon counting can be achieved by processing the resulting image, taken in a continuous readout mode. Based on Geant4 simulations, by considering a realistic detector design and response, it is shown that photon rates up to at least 1011 photons s−1 on‐sample (5 µm water‐equivalent cell) can be processed, limited by the spatial diffusion of the photoelectrons in the gas. Illustratively, if making use of the Rose criterion and assuming the dose partitioning theorem, it is shown how such a detector would allow obtaining 3D images of 5 µm‐size unstained cells in their native environment in about 24 h, with a resolution of 36 nm. [ABSTRACT FROM AUTHOR]

A synchrotron‐based technique using Compton scattering imaging is presented. This technique has been applied to a coin battery (CR2023), and the cross‐sectional image has been obtained in 34 ms without sample rotation. A three‐dimensional image of the whole structure has been reconstructed from 74 cross‐sectional images taken consecutively by scanning the incident, wide X‐ray beam along one direction. This work demonstrates that quick cross‐sectional imaging of regions of interest and three‐dimensional image reconstruction without sample rotation are feasible using Compton scattering imaging. [ABSTRACT FROM AUTHOR]

The screening parameter (Z‐S) of a self‐consistent field of 1s electrons was experimentally determined for Be, B, and C atoms and for atoms with the number Z ≤ 9 included in the LiF, Li2CO3, Li4B4O7, B4C, B2O3, H2O, and C2H6O compounds. The determination was made by the experimental dependence of the ratio of the intensities of Rayleigh and Compton scattering on the momentum transfer variable in the range from 0.70 to 1.67 Å−1. For single‐component materials, the experimental (Z‐S) values correspond to theoretical values for the free atoms. For the atoms bonded in the compound, the (Z‐S) value depends on the composition of the compound and characterizes the interaction between electrons. The obtained experimental (Z‐S) data were used to calculate the electronegativity of bonded atoms and the deformation of their K‐shell was determined. [ABSTRACT FROM AUTHOR]

Compton scattering is generally neglected in diffraction experiments because the incoherent radiation it generates does not give rise to interference effects and therefore is negligible at Bragg peaks. However, as the scattering volume is reduced, the difference between the Rayleigh (coherent) and Compton (incoherent) contributions at Bragg peaks diminishes and the incoherent part may become substantial. The consequences can be significant for coherent diffraction imaging at high scattering angles: the incoherent radiation produces background that smears out the secondary interference fringes, affecting thus the achievable resolution of the technique. Here, a criterion that relates the object shape and the resolution is introduced. The Compton contribution for several object shapes is quantified, and it is shown that the maximum achievable resolution along different directions has a strong dependence on the crystal shape and size. [ABSTRACT FROM AUTHOR]

Purpose: To demonstrate that variation in chemical composition has a negligible effect on the mapping curve from relative electron density (RED) to proton stopping power ratio (SPR), and to establish the theoretical framework of using Megavoltage (MV) computed tomography (CT), instead of kilovoltage (kV) dual energy CT, to accurately estimate proton SPR. Methods: A simulation study was performed to evaluate the effect of chemical composition variation on kVCT number and proton SPR. The simulation study involved both reference and simulated human tissues. The reference human tissues, together with their physical densities and chemical compositions, came from the ICRP publication 23. The simulated human tissues were created from the reference human tissues assuming that elemental percentage weight followed a Gaussian distribution. For all tissues, kVCT number and proton SPR were obtained through (a) theoretical calculation from tissue's physical density and chemical composition which served as the ground truth, and (b) estimation from RED using the calibration curves established from the stoichiometric method. Deviations of the estimated values from the calculated values were quantified as errors in using RED to estimate kVCT number and proton SPR. Results: Given a chemical composition variation of 5% (1σ) of the nominal percentage weights, the total estimation error of using RED to estimate kVCT number was 0.34%, 0.62%, and 0.77% and the total estimation error of using RED to estimate proton SPR was 0.30%, 0.22%, and 0.16% for fat tissues, non‐fat soft tissues and bone tissues, respectively. Conclusion: Chemical composition had a negligible effect on the method of using RED to determine proton SPR. RED itself is sufficient to accurately determine proton SPR. MVCT number maintains a superb linear relationship with RED because it is highly dominated by Compton scattering. Therefore, MVCT has great potential in reducing the proton range uncertainty. [ABSTRACT FROM AUTHOR]

High‐resolution (0.12 a.u.) electron momentum density projections (Compton profiles) of a hexagonal Zn single crystal have been measured along five high‐symmetry directions in reciprocal space. The experiment was performed with the use of 115.6 keV synchrotron radiation on the BL08W station at SPring‐8. The quality of the measured Compton profiles is significantly better than that of previous medium‐ and high‐resolution data. The experimental data were compared with the corresponding theoretical Korringa–Kohn–Rostoker (KKR) and density functional theory (DFT) calculations. Some minor and major differences between the two theoretical band‐structure calculations have been observed. However, the good quality experimental results indicate their better agreement with DFT. [ABSTRACT FROM AUTHOR]

Cygnus X‐3 (Cyg X‐3) is the famous binary system containing a black hole. It is actively studied through the wide range of electromagnetic spectra from radio band up to ultrahigh energies. Cyg X‐3 has long been considered an object for very high energy gamma‐ray observations. We present the results of more than 20‐year‐long studies of Cyg X‐3 in the range of 800 GeV to 100 TeV with the SHALON telescope. The detected TeV γ‐ray source was identified with Cyg X‐3 based on the detection of the γ‐ray flux modulation during the orbital period of this binary system of 4.8 hr. The detected modulation of TeV γ‐ray emission with orbit, together with the high luminosity of the companion star of Cyg X‐3 and the close orbit, leads to the efficient generation of the part of γ‐ray emission in the inverse Compton scattering. The correlation of TeV flux increases with the flaring activity of Cyg X‐3 in X‐ray and radio ranges is found, which could be associated with powerful mass ejections from the central regions around the black hole. [ABSTRACT FROM AUTHOR]

In high‐energy astrophysics scenarios such as Blazars, gamma‐ray bursts, or pulsar wind nebulae, it is highly probable that ultrarelativistic particles interact with photons in their environment through scattering. As long as the energy of the particle is greater than the energy of the interacting photon, the (classical) scattering is known to be in the Thomson regime. Otherwise, quantum effects will affect the scattering cross section, and we enter into the so‐called Klein‐Nishina regime. It is well known that radiative cooling in the Thomson regime is very efficient, leading to soft high‐energy spectra. However, observations have shown that, in many cases, the high‐energy spectrum of some objects is rather hard. This has led to the assumption that perhaps particles are not being cooled down efficiently. Asymptotic approximations of the Klein‐Nishina regime have been formulated in the last decades in order to account for these corrections in the distribution of particles responsible for the observed spectrum of high‐energy sources. In this work, we present a numerical approach of the Klein‐Nishina corrections to the radiative cooling. It has been developed to simulate the evolution of a distribution of particles interacting with photons in their surroundings via inverse Compton scattering. [ABSTRACT FROM AUTHOR]

X‐ray Compton scattering measurements using synchrotron radiation are carried out for liquid sodium (Na) from 473 K up to 1273 K. Utilizing the liquid state allows us to realize a continuous density reduction by controlling temperature and pressure. Valence Compton profiles (CPs) clearly exhibit thermodynamic state dependence as the temperature increases. Experimental CPs, CP differences, and electron kinetic energy are compared with those of the electron gas model. Combined with the analysis using the Fourier‐transformed CPs, the observed behaviors can be reasonably explained by the reduction in the electron density with volume expansion of the liquid. [ABSTRACT FROM AUTHOR]

Purpose: Ionization chambers are widely used for dosimetry with megavoltage photon beams. Several properties of ionization chambers, including the cable effect, polarity effect, and ion recombination loss, are described in standard dosimetry protocols. The cable effect is categorized as the leakage current and Compton current, and careful consideration of these factors has been described not only in reference dosimetry but also in large fields. However, the mechanism of Compton current in the cable has not been investigated thoroughly. The cable effect of ionization chambers in 6 MV X‐ray beam was evaluated by measurement, and the mechanism of Compton current was investigated by Monte Carlo simulation. Materials and Methods: Four PTW ionization chambers (TM30013, TM31010, TM31014, and TM31016) with the same type of mounted cable, but different ionization volumes, were used to measure output factor (OPF) and cable effect measurement. The OPF was measured to observe any variation resulting from the cable effect. The cable effect was evaluated separately for the leakage current and Compton current, and its charge per absorbed dose to water per cable length was estimated by a newly proposed method. The behavior of electrons and positrons in the core wire was analyzed and the Compton current for the photon beam was estimated by Monte Carlo simulation. Results: In OPF measurement, the difference in the electrometer readings by polarity became obvious for the mini‐ or microchamber and its difference tended to be larger for a chamber with a smaller ionization volume. For the cable effect measurement, it was determined that the contribution of the leakage current to the cable effect was ignorable, while the Compton current was dominant. The charge due to the Compton current per absorbed dose to water per cable length was estimated to be 0.36 ± 0.03 pC Gy−1 cm−1 for PTW ionization chambers. As a result, the contribution of the Compton current to the electrometer readings was estimated to be 0.002% cm−1 for the Farmer‐type, 0.011% cm−1 for the scanning, and 0.088% cm−1 for microchambers, respectively. By the simulation, it was determined that the Compton current for MV x‐ray could be explained by not only recoil electrons due to Compton scattering but also positron due to pair production. The Compton current estimated by the difference in outflowing and inflowing charge was 0.45 pC Gy−1 cm−1 and was comparable with the measured value. Conclusion: The cable effect, which includes the leakage current and Compton current, was quantitatively estimated for several chambers from measurements, and the mechanism of Compton current was investigated by Monte Carlo simulation. It was determined that the Compton current is a dominant component of the cable effect and its charge is consistently positive and nearly the same, irrespective of the ionization chamber volume. The contribution of Compton current to the electrometer readings was estimated for chambers. The mechanism of Compton current was analyzed and it was confirmed that the Compton current can be estimated from the difference in outflowing and inflowing charge to and from the core wire. [ABSTRACT FROM AUTHOR]

Purpose: X‐ray microbeam radiation therapy is a preclinical concept for tumor treatment promising tissue sparing and enhanced tumor control. With its spatially separated, periodic micrometer‐sized pattern, this method requires a high dose rate and a collimated beam typically available at large synchrotron radiation facilities. To treat small animals with microbeams in a laboratory‐sized environment, we developed a dedicated irradiation system at the Munich Compact Light Source (MuCLS). Methods: A specially made beam collimation optic allows to increase x‐ray fluence rate at the position of the target. Monte Carlo simulations and measurements were conducted for accurate microbeam dosimetry. The dose during irradiation is determined by a calibrated flux monitoring system. Moreover, a positioning system including mouse monitoring was built. Results: We successfully commissioned the in vivo microbeam irradiation system for an exemplary xenograft tumor model in the mouse ear. By beam collimation, a dose rate of up to 5.3 Gy/min at 25 keV was achieved. Microbeam irradiations using a tungsten collimator with 50 μm slit size and 350 μm center‐to‐center spacing were performed at a mean dose rate of 0.6 Gy/min showing a high peak‐to‐valley dose ratio of about 200 in the mouse ear. The maximum circular field size of 3.5 mm in diameter can be enlarged using field patching. Conclusions: This study shows that we can perform in vivo microbeam experiments at the MuCLS with a dedicated dosimetry and positioning system to advance this promising radiation therapy method at commercially available compact microbeam sources. Peak doses of up to 100 Gy per treatment seem feasible considering a recent upgrade for higher photon flux. The system can be adapted for tumor treatment in different animal models, for example, in the hind leg. [ABSTRACT FROM AUTHOR]

Inverse Compton scattering provides means to generate low‐divergence partially coherent quasi‐monochromatic, i.e. synchrotron‐like, X‐ray radiation on a laboratory scale. This enables the transfer of synchrotron techniques into university or industrial environments. Here, the Munich Compact Light Source is presented, which is such a compact synchrotron radiation facility based on an inverse Compton X‐ray source (ICS). The recent improvements of the ICS are reported first and then the various experimental techniques which are most suited to the ICS installed at the Technical University of Munich are reviewed. For the latter, a multipurpose X‐ray application beamline with two end‐stations was designed. The beamline's design and geometry are presented in detail including the different set‐ups as well as the available detector options. Application examples of the classes of experiments that can be performed are summarized afterwards. Among them are dynamic in vivo respiratory imaging, propagation‐based phase‐contrast imaging, grating‐based phase‐contrast imaging, X‐ray microtomography, K‐edge subtraction imaging and X‐ray spectroscopy. Finally, plans to upgrade the beamline in order to enhance its capabilities are discussed. [ABSTRACT FROM AUTHOR]

Summary: Electron Compton scattering is a technique that gives information on the electron momentum density of states and is used to characterize the ground state electronic structure in solids. Extracting the momentum density of states requires us to assume the so‐called 'impulse approximation', which is valid for large energy losses. Here, the robustness of the impulse approximation in the low energy transfer regime is tested and confirmed on amorphous carbon films. Compared to traditional Compton measurements, this provides additional benefits of more efficient data collection and a simplified way to probe valence electrons, which govern solid state bonding. However, a potential complication is the increased background from the plasmon signal. To overcome this, a novel plasmon background subtraction routine is proposed for samples that are resistant to beam damage. Lay Description: Properties of solids depend on their electronic structure which can be studied using electron Compton scattering technique. Here, an electron beam is used to penetrate a very thin sample. During the interaction between the electrons in the beam and electrons in the sample, the former transfer a part of their energy to the latter, resulting in a measurable energy loss of the transmitted beam. The amount of the energy transfer depends on the angle of incidence between the beam and the sample. Typically, the experiments are carried out using high tilt angles and high energy transfer; however, in this work, we show that even smaller angles of incidence are suitable, which improve the signal quality and ease data processing procedures. [ABSTRACT FROM AUTHOR]

Purpose: Real‐time visualization of target motion using fiducial markers during radiation therapy treatment will allow for more accurate dose delivery. The purpose of this study was to optimize techniques for online fiducial marker tracking by detecting the scattered treatment beam through coded aperture imaging (CAI). Coded aperture imaging is a novel imaging technique that can allow target tracking in real time during treatment, and do so without adding any additional radiation dose, by making use of the scattered treatment beam radiation. Methods: Radiotherapy beams of various energies, incident on phantoms containing gold fiducial markers were modeled using MCNP6.2 Monte Carlo transport code. Orthogonal scatter radiographs were collected through a CAI geometry. After decoding the simulated radiograph data, the centroid location and FWHM/SNR of the fiducial signals were analyzed. The effects of properties related to the CA (rank, pattern, and physical dimensions), detector (dimensions and pixel count), position (CA and phantom), and the incident beam (spectrum and direction) were investigated. These variables were evaluated by quantifying the positional accuracy, resolution, and SNR of the fiducials' signal. The effects of phantom scatter and decoding artifacts were reduced via Fourier filtering to avoid treatment interruption and physical interaction with the coded mask. Results: The method was able to accurately localize the markers to within 1 pixel of a simulated radiograph. A 10 × 10 × 2 cm tungsten mask was chosen to attenuate >99 % of incident scatter through opaque elements, while minimizing collimation artifacts which arise from vignetting of the coded radiograph. Clear separation of centroids from fiducial signals with 2.5 mm separation was maintained, and initial optimization of parameters has produced an aperture which decodes the location of multiple fiducial markers inside a human phantom properly with a high SNR in the final radiograph image. Conclusion: Current results show a proof of concept for a novel real‐time imaging method. Coded aperture imaging is a promising technique for extracting the fiducial scatter signal from a broader Compton‐scatter background. These results can be used to further optimize the CAI parameter space and guide fabrication and testing of a clinical device. [ABSTRACT FROM AUTHOR]

A generalization of the Compton method for determining elements with a low atomic number Z from 1 (H) to 9 (F) by the ratio ICIR of the intensities of incoherent (Compton) and coherent (Rayleigh) scattering is proposed. The generalization takes into account not only the dependence of this ratio on the effective atomic number of the scatterer material but also the momentum transfer variable x = sinθλ. The new method is based on the application of calibration function of ICIR=gZ,x obtained by measuring scattering spectra at two values of x1= 0.831 Å−1 and x2= 1.297 Å−1 with a WDXRF spectrometer. The elemental atomic numbers and their concentrations of binary compounds with unknown compositions are determined by the solution of a system of linear equations. Coefficients of the equations are calculated from the measured ICIR ratios for the test sample and the regularization solution for the corresponding calibration. The experiments have been carried out for standard samples of single‐component, binary and triple stoichiometric compounds based on H, Li, Be, B, C, O and F. The identification of these elements was found to be possible in the absence of a relationship between the positions of scattering peaks and the composition of the sample, and a qualitative and quantitative analysis of the composition of the material was carried out as part of the solution of a single inverse problem. [ABSTRACT FROM AUTHOR]

A Thomson scattering X‐ray source can provide quasi‐monochromatic, continuously energy‐tunable, polarization‐controllable and high‐brightness X‐rays, which makes it an excellent tool for X‐ray fluorescence computed tomography (XFCT). In this paper, we examined the suppression of Compton scattering background in XFCT using the linearly polarized X‐rays and the implementation feasibility of linearly polarized XFCT based on this type of light source, concerning the influence of phantom attenuation and the sampling strategy, its advantage over K‐edge subtraction computed tomography (CT), the imaging time, and the potential pulse pile‐up effect by Monte Carlo simulations. A fan beam and pinhole collimator geometry were adopted in the simulation and the phantom was a polymethyl methacrylate cylinder inside which were gadolinium (Gd)‐loaded water solutions with Gd concentrations ranging from 0.2 to 4.0 wt%. Compared with the case of vertical polarization, Compton scattering was suppressed by about 1.6 times using horizontal polarization. An accurate image of the Gd‐containing phantom was successfully reconstructed with both spatial and quantitative identification, and good linearity between the reconstructed value and the Gd concentration was verified. When the attenuation effect cannot be neglected, one full cycle (360°) sampling and the attenuation correction became necessary. Compared with the results of K‐edge subtraction CT, the contrast‐to‐noise ratio values of XFCT were improved by 2.03 and 1.04 times at low Gd concentrations of 0.2 and 0.5 wt%, respectively. When the flux of a Thomson scattering light source reaches 1013 photons s−1, it is possible to finish the data acquisition of XFCT at the minute or second level without introducing pulse pile‐up effects. [ABSTRACT FROM AUTHOR]

Compton to Rayleigh scattering intensity ratios (IC/IR) have been measured using X‐rays with energy 17.44 keV for single‐component materials with atomic number Z from 4 (Be) to 31 (Ga) and binary compounds of stoichiometric composition. The measurements have been performed using two optical schemes: an energy‐dispersive X‐ray fluorescence scheme with a molybdenum secondary target and wavelength‐dispersive X‐ray fluorescence one. The processing of the spectra was carried out by fitting with Pearson VII functions. For single‐component and binary standards, the experimental dependence of the scattering intensity ratio on the atomic number was found to be the same. This confirms the additivity of the contribution of different atoms to the scattering. The dependence has a complex shape but is well described by the theoretical relationship for IC/IR with correction on the difference between Compton and Rayleigh radiation absorption coefficients. Two ranges of atomic number values are defined, in which the effective atomic number Zeff can be determined by the calibration method using this dependence: for Z from 4 to 7 with low error of ΔZeff =±0.15 and for Zeff from 10 to 18 with low error of ΔZeff =±0.69. A change in the shape of the Compton peak and an overestimated value of the of the Compton and Rayleigh peak intensity ratio when passing from a single‐component scatterer (Al or Si) to their oxides Al2O3 or SiO2, respectively, have been revealed. [ABSTRACT FROM AUTHOR]

Small‐animal physiology studies are typically complicated, but the level of complexity is greatly increased when performing live‐animal X‐ray imaging studies at synchrotron and compact light sources. This group has extensive experience in these types of studies at the SPring‐8 and Australian synchrotrons, as well as the Munich Compact Light Source. These experimental settings produce unique challenges. Experiments are always performed in an isolated radiation enclosure not specifically designed for live‐animal imaging. This requires equipment adapted to physiological monitoring and test‐substance delivery, as well as shuttering to reduce the radiation dose. Experiment designs must also take into account the fixed location, size and orientation of the X‐ray beam. This article describes the techniques developed to overcome the challenges involved in respiratory X‐ray imaging of live animals at synchrotrons, now enabling increasingly sophisticated imaging protocols. [ABSTRACT FROM AUTHOR]

Constructing a quantum description of crystals from scattering experiments is of great significance to explain their macroscopic properties and to evaluate the pertinence of theoretical ab initio models. While reconstruction methods of the one‐electron reduced density matrix have already been proposed, they are usually tied to strong assumptions that limit and may introduce bias in the model. The goal of this paper is to infer a one‐electron reduced density matrix (1‐RDM) with minimal assumptions. It has been found that the mathematical framework of semidefinite programming can achieve this goal. Additionally, it conveniently addresses the nontrivial constraints on the 1‐RDM which were major hindrances for the existing models. The framework established in this work can be used as a reference to interpret experimental results. This method has been applied to the crystal of dry ice and provides very satisfactory results when compared with periodic ab initio calculations. [ABSTRACT FROM AUTHOR]

Purpose: Xtrim‐PET is a newly designed Silicon Photomultipliers (SiPMs)‐based prototype PET scanner dedicated for small laboratory animal imaging. We present the performance evaluation of the Xtrim‐PET scanner following NEMA NU‐4 2008 standards to help optimizing scanning protocols which can be achieved through standard and reliable system performance characterization. Methods: The performance assessment was conducted according to the National Electrical Manufacturers Association (NEMA) NU‐4 2008 standards in terms of spatial resolution, sensitivity, counting rate performance, scatter fraction and image quality. The in vivo imaging capability of the scanner is also showcased through scanning a normal mouse injected with 18F‐FDG. Furthermore, the performance characteristics of the developed scanner are compared with commercially available systems and current prototypes. Results: The volumetric spatial resolution at 5 mm radial offset from the central axis of the scanner is 6.81 µl, whereas a peak absolute sensitivity of 2.99% was achieved using a 250–650 keV energy window and a 10 ns timing window. The peak noise‐equivalent count rate (NECR) using a mouse‐like phantom is 113.18 kcps at 0.34 KBq/cc with 12.5% scatter fraction, whereas the NECR peaked at 82.76 kcps for an activity concentration level of 0.048 KBq/cc with a scatter fraction of 25.8% for rat‐like phantom. An excellent uniformity (3.8%) was obtained using NEMA image quality phantom. Recovery coefficients of 90%, 86%, 68%, 40% and 12% were calculated for rod diameters of 5, 4, 3, 2 and 1 mm, respectively. Spill‐over ratios for air‐filled and water‐filled chambers were 35% and 25% without applying any correction for attenuation and Compton scattering effects. Conclusion: Our findings revealed that beyond compactness, lightweight, easy installation and good energy resolution, the Xtrim‐PET prototype presents a reasonable performance making it suitable for preclinical molecular imaging‐based research. [ABSTRACT FROM AUTHOR]

In this article, we discuss a scaling function for the cross section in deeply virtual compton scattering (DVCS) and exclusive vector meson production in both γ*p and γ*A processes. Our description relies on the geometric scaling phenomenon in which cross sections are a function of a single variable τ=Q2/Qs2, where Q2 is the photon virtuality and Qs2 represents the saturation scale that drives the energy dependence and nuclear effects. We make a prediction to be tested in future electron–ion colliders. [ABSTRACT FROM AUTHOR]

Compact X‐ray sources based on inverse Compton scattering provide brilliant and partially coherent X‐rays in a laboratory environment. The cross section for inverse Compton scattering is very small, requiring high‐power laser systems as well as small laser and electron beam sizes at the interaction point to generate sufficient flux. Therefore, these systems are very sensitive to distortions which change the overlap between the two beams. In order to monitor X‐ray source position, size and flux in parallel to experiments, the beam‐position monitor proposed here comprises a small knife edge whose image is acquired with an X‐ray camera specifically designed to intercept only a very small fraction of the X‐ray beam. Based on the source position drift recorded with the monitor, a closed‐loop feedback stabilizes the X‐ray source position by adjusting the laser beam trajectory. A decrease of long‐term source position drifts by more than one order of magnitude is demonstrated with this device. Consequently, such a closed‐loop feedback system which enables stabilization of source position drifts and flux of inverse Compton sources in parallel to experiments has a significant impact on the performance of these sources. [ABSTRACT FROM AUTHOR]

Biogeochemistry interface process in a plant–soil (rock) system normally takes a key role in environmental processes. It involves complex mediums relating with complex crucial physical, chemical, and biological interactions. Accurate description of element distribution characteristics in interfaces and combination media is the prerequisite for revealing elements transfer and transformation processes. In situ micro‐X‐ray fluorescence is used here to describe the localizations of elements in a bryophyte–soil–rock interface involving biological (plant) and geological (soil and rock) matrixes. It is shown that matrix effects get great influence on the localization characteristics in this interface. Spectra without matrix corrections shows that Zn, Cu, Fe, Ca, and K reach maximum concentrations in different interface layers. Compton to Rayleigh ratio (Com/Ray), relating with mean atomic number (mean Z) and mass attenuation coefficients, has been applied in matrix correction, whereas other correction methods like multiplied or divided by Com or Ray were compared here too. The results show that the correction method with Ray*Ray/Com is more suitable for describing reasonable Ca, Mn, Fe, Zn, Cu, and Pb localization characteristics in this interface, whereas correction with Ray/Com is better for K. The localization characters after ideal corrections show that K, Ca, Pb, Zn, and Cu reach their maximum peaks at the soil layer in the interface, which are much more reasonable than the results without corrections. [ABSTRACT FROM AUTHOR]

X‐ray fluorescence (XRF) is a widely used method for in vivo elemental analysis. Particularly for bone, it is a non‐invasive technique that provides information on composition without significant risk to the patient. XRF contributes a capability for measuring elements beneficial to human health, such as strontium. This is a proposed supplement that has been shown in clinical trials to reduce fracture risk in people diagnosed with osteoporosis. Although XRF is a viable method for quantifying bone strontium, there are still factors that constrain its effectiveness. X‐ray attenuation through overlying soft tissue decreases the signal, consequently requiring correction before estimating the true concentration of strontium in bone. A correction factor can be applied to account for the reduced signal, but an accurate measurement of overlying soft tissue thickness is required. It has been shown that using the correlation between Compton peak count rate and overlying thickness can be used as an estimation of overlying tissue. Lucite is commonly used as a soft tissue substitute; however, its mean atomic number is appreciably lower than soft tissue, somewhat limiting its applicability. This study tests the feasibility of using cellulose filter papers as a substitute for overlying soft tissue to perform XRF analysis of strontium‐doped hydroxyapatite bone phantoms. Mass attenuation coefficients are shown to be closer to those of soft tissue (International Commission on Radiation Units' four‐component) than Lucite, and the Compton correlation is used to estimate thickness as a correction factor to quantify true strontium concentration. [ABSTRACT FROM AUTHOR]

Terrestrial gamma‐ray flashes (TGFs) are high‐energy photon bursts originating from the Earth's atmosphere. In this study, using first‐principles Monte Carlo simulations, we quantify the effects of Compton scattering on the temporal and spectral properties of TGFs induced by a tilted source geometry. Modeling results indicate that the source orientation is a critical parameter in TGF analysis but has been significantly underestimated in previous studies. Offset distance between the lightning source and satellite location cannot be used as a single parameter characterizing Compton scattering effects. In the tilted geometry, Compton scattering effects are more pronounced in the falling part of TGF pulses and can lead to an increase of the falling part of TGF pulses by several tens of microseconds. Moreover, by performing curve‐fitting analysis on simulated TGF light curves, we explain how the symmetric and asymmetric pulses measured by the Gamma‐Ray Burst Monitor on Fermi satellite are consistent with the Compton scattering effects. Fermi‐measured TGF pulses can be fully explained using Gaussian‐distributed TGF sources with an average duration of ∼206 μs. Key Points: We quantify the Compton scattering effects in terms of temporal dispersion and energy spectra produced by tilted TGF geometryOffset distance between lightning source and satellite cannot be used as a single parameter characterizing Compton scattering effectsWe show that Fermi‐measured TGF pulses, including the asymmetric ones with longer rise time, are consistent with Compton scattering effect [ABSTRACT FROM AUTHOR]

Composed of hydrocarbons and other substances, petroleum is classified as a nonrenewable source of energy. In its unrefined form, it is called crude oil. Currently, its derivates are widely used in domestic and industrial environments, with the greatest exponent being motor fuels and lubricating oils. Due to the overwhelming demand, new oil wells in the presalt region of Brazil are going to be drilled, which will, in its turn, increase the demand for analysis and require the use of less costly technologies. The purpose of this paper is to present an experimental method that aims at characterizing crude oil samples through their X‐ray scattering profiles without the need for any chemical preparation to be performed in advance, which will enable this method to be used for analyzing samples immediately after their extraction. For the experiment, a portable X‐ray scattering system composed by an X‐ray tube (silver anode) and a Si‐PIN detector was used in order to analyze samples from different wells. The process consisted in establishing a linear relationship between the effective atomic number and the ratio between peak intensities of Compton and Rayleigh scattering from known samples. The linear function, verified experimentally, was then applied to samples of crude oil, and the results showed that it is possible to characterize them on the basis of the Rayleigh to Compton scattering ratio. After the analysis, a multiple comparison test performed on the samples proved that this methodology indeed allows to differentiate samples of different origins and to verify the compatibility of samples extracted from the same well. [ABSTRACT FROM AUTHOR]

Powerful radio sources and quasars emit relativistic jets of plasma and magnetic fields that travel hundreds of kiloparsecs, ultimately depositing energy into the intra‐ or inter‐cluster medium. In the rest frame of the jet, the energy density of the cosmic microwave background is enhanced by the bulk Lorentz factor as Γ2, and when this exceeds the magnetic energy density the primary loss mechanism of the relativistic electrons is via inverse Compton scattering. The microwave energy density is also enhanced by a factor (1 + z)4, which becomes important at large redshifts. We are surveying a z > 3 subsample of radio sources selected with centimeter‐wavelength flux density >70 mJy, and with a spectroscopic redshift. Out of the first 12 objects observed, there are two clear cases of the X‐rays extending beyond the detectable radio jet. [ABSTRACT FROM AUTHOR]

The paper addresses the recent progress in study of light yield behavior in scintillators based on solid solutions (mixed crystals), which are among the brightest known scintillators. Following the prior work [O. Sidletskiy et al., Phys. Status Solidi A 2014, 211, 2384], the extended phenomenological analysis of the correlations between light yield behavior and physical properties of mixed crystals (band gaps of the components, ionic radii, and atomic weights of the substitutional atoms) is carried out. The trend to light yield enhancement is notable in systems with the substitution of atoms in two non‐equivalent crystallographic sites in the lattice leading to formation of planes and columns enriched with one of the substitutional atoms. This evidences an important role of nanoscale spatial inhomogeneity (domains or clusters) in scintillation process in mixed scintillators. A roadmap of search for new bright scintillators is proposed basing on the established trends. [ABSTRACT FROM AUTHOR]

Purpose: Lung stereotactic body radiation therapy (SBRT) requires delivering large radiation doses with millimeter accuracy, making image guidance essential. An approach to forming images of patient anatomy from Compton‐scattered photons during lung SBRT is presented. Methods: To investigate the potential of scatter imaging, a pinhole collimator and flat‐panel detector are used for spatial localization and detection of photons scattered during external beam therapy using lung SBRT treatment conditions (6 MV FFF beam). MCNP Monte Carlo software is used to develop a model to simulate scatter images. This model is validated by comparing experimental and simulated phantom images. Patient scatter images are then simulated from 4DCT data. Results: Experimental lung tumor phantom images have sufficient contrast‐to‐noise to visualize the tumor with as few as 10 MU (0.5 s temporal resolution). The relative signal intensity from objects of different composition as well as lung tumor contrast for simulated phantom images agree quantitatively with experimental images, thus validating the Monte Carlo model. Scatter images are shown to display high contrast between different materials (lung, water, bone). Simulated patient images show superior (~double) tumor contrast compared to MV transmission images. Conclusions: Compton scatter imaging is a promising modality for directly imaging patient anatomy during treatment without additional radiation, and it has the potential to complement existing technologies and aid tumor tracking and lung SBRT image guidance. [ABSTRACT FROM AUTHOR]

Nondestructive assays are essentials for certain types of sample materials, and, among those, the X-ray fluorescence technique enables the determinations of stable elements, and there is an increasing effort on the development of equipment to suit the various needs. Nevertheless, a great difficulty on the analysis of unknown materials' composition is to account for self-absorption of the fluorescence photons that must be considered in the elemental concentration calculation. The correlation between the Rayleigh to Compton scattering ratio to the mass attenuation coefficient has proved to follow a single polynomial function for the first 20 elements of the periodical table with a correlation factor higher than of 0.998 for the sixth order function. The Rayleigh to Compton scattering ratios for pure elements and the 22.16 keV photons, the main energy from an X-ray tube with silver anode, were determined with the MCNP6 Monte Carlo computer code. Two scattering angles were considered. Reference samples were measured, and the calculated results were compared to the literature values of the mass attenuation coefficient for some known samples and showed to be within 20% for de 90° scattering angle. Only Lucite was slightly above 20%. Curve fit coefficients are also presented for the 7.11- and 17.40-keV photon energies. [ABSTRACT FROM AUTHOR]

Compton scattering initially occurs, resulting in electron ionization and the scattering of a lower-energy X-ray photon. The resultant electrons and photons interact within the material, instigating a cascade that produces hundreds to thousands of electron-hole pairs. This illustration portrays the effect of Co-60 gamma ray radiation on piezoelectric microelectromechanical resonators. [Extracted from the article]