Search

We report on the quantitative nondestructive analysis of the natural isotopic abundances of hafnium and tungsten elements using nuclear resonance fluorescence. Metallic samples of hafnium and tungsten were irradiated to six quasi-monochromatic γ -ray beams generated by laser Compton scattering in the energy range of 2.4–3.2 MeV. Multiple nuclei were simultaneously excited at each of the six γ -ray beam energies. A high-purity germanium detector array detected deexcitations of the nuclei. In total, 51 transitions were unprecedentedly employed to estimate the isotopic abundances of heavy elements nondestructively. The estimated abundances of three hafnium isotopes and three tungsten isotopes are consistent with standard known natural abundances within the experimental uncertainties. The deviation from the standard values ranges from 0.18 % to 1.36 %. [ABSTRACT FROM AUTHOR]

Our Compton profile measurements of Ti and TiH2 using readily available hard X-ray radiation at 27.5 keV, detected by both a Hitachi Vortex silicon-drift detector and a high-resolution superconducting transition-edge sensor array, are found to be in excellent accord with state-of-the-art density functional theory based calculations. The spherically averaged difference between the Compton profiles of TiH2 and Ti is well described by an inverted parabola, supporting an itinerant behavior of the electron gas screening the protons in the Ti matrix. Our experimental approach, validated by two different detectors, extends the applicability of Compton scattering technique to the readily accessible hard x-ray regime (below 30 keV). Our study suggests possibilities for experiments at low-flux bending magnet synchrotron beamlines and paves the way for the development of tabletop Compton experiments with x-ray tubes. [ABSTRACT FROM AUTHOR]

Context. Spiral galaxies M31 and M33 are among the γ-ray sources detected by the Fermi Large Area Telescope (LAT). Aims. We aim to model the broadband non-thermal emission of the central region of M31 (a LAT point source) and of the disk of M33 (a LAT extended source), as part of our continued survey of non-thermal properties of local galaxies that includes the Magellanic Clouds. Methods. We analysed the observed emission from the central region of M31 (R < 5.5 kpc) and the disk-sized emission from M33 (R ∼ 9 kpc). For each galaxy, we self-consistently modelled the broadband spectral energy distribution of the diffuse non-thermal emission based on published radio and γ-ray data. All relevant radiative processes involving relativistic and thermal electrons (synchrotron, Compton scattering, bremsstrahlung, and free–free emission and absorption), along with relativistic protons (π0 decay following interaction with thermal protons), were considered, using exact emissivity formulae. We also used the Fermi-LAT-validated γ-ray emissivities for pulsars. Results. Joint spectral analyses of the emission from the central region of M31 and the extended disk of M33 indicate that the radio emission is composed of both primary and secondary electron synchrotron and thermal bremsstrahlung, whereas the γ-ray emission may be explained as a combination of diffuse pionic, pulsar, and nuclear-BH-related emissions in M31 and plain diffuse pionic emission (with an average proton energy density of 0.5 eV cm−3) in M33. Conclusions. The observed γ-ray emission from M33 appears to be mainly hadronic. This situation is similar to other local galaxies, namely, the Magellanic Clouds. In contrast, we have found suggestions of a more complex situation in the central region of M31, whose emission could be an admixture of pulsar emission and hadronic emission, with the latter possibly originating from both the disk and the vicinity of the nuclear black hole. The alternative modelling of the spectra of M31 and M33 is motivated by the different hydrogen distribution in the two galaxies: The hydrogen deficiency in the central region of M31 partially unveils emissions from the nuclear BH and the pulsar population in the bulge and inner disk. If this were to be the case in M33 as well, these emissions would be outshined by diffuse pionic emission originating within the flat central-peak gas distribution in M33. [ABSTRACT FROM AUTHOR]

High-brilliance high-polarization γ rays based on Compton scattering are of great significance in broad areas, such as nuclear physics, high-energy physics, astrophysics, etc. However, the transfer mechanism of spin angular momentum in the transition from linear through weakly into strongly nonlinear processes is still unclear, which severely limits the simultaneous control of brilliance and polarization of high-energy γ rays. In this work, we clarify the transfer mechanism in the transition regions and put forward a clear way to efficiently manipulate the polarization of emitted photons. We find that to simultaneously generate high-energy, high-brilliance, and high-polarization γ rays, it is better to increase the laser intensity for the initially spin-polarized electron beam. However, for the case of employing the initially spin-nonpolarized electron beam, in addition to increasing laser intensity, it is also necessary to increase the energy of the electron beam. Because the γ photon polarization emitted through the single-photon absorption channel is mainly attributed to the spin transfer of laser photons, while in multi-photon absorption channels, the electron spin plays a major role. Moreover, we confirm that the signature of γ-ray polarization can be applied to observing the nonlinear effects (multi-photon absorption) of Compton scattering with moderate-intensity laser facilities. [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]

In medical applications—such as positron emission tomography (PET)—511 keV photons that experience Compton scattering are studied. We present a consistent framework based on quantum error-correction channels—intensively studied in quantum computing—to fully describe the quantum information-theoretic content of high energetic photons undergoing Compton scattering, characterized by the Klein–Nishina formula in unoriented matter. In this way, we can predict the expected spatial distribution of two or more, pure or mixed, polarization entangled or separable photons. This framework allows us to characterize the accessible and inaccessible information for different parameter ranges. It also answers the question of how to describe successive multi-photon scattering. In addition our formalism provides a complete framework for dealing with single and all multi-partite errors that can occur in the propagation, providing the basis for modeling future dedicated experiments that will then have applications in medicine, such as reducing errors in PET imaging or exploring possibilities for quantum-based diagnostic indicators. [ABSTRACT FROM AUTHOR]

In medical applications—such as positron emission tomography (PET)—511 keV photons that experience Compton scattering are studied. We present a consistent framework based on quantum error-correction channels—intensively studied in quantum computing—to fully describe the quantum information-theoretic content of high energetic photons undergoing Compton scattering, characterized by the Klein–Nishina formula in unoriented matter. In this way, we can predict the expected spatial distribution of two or more, pure or mixed, polarization entangled or separable photons. This framework allows us to characterize the accessible and inaccessible information for different parameter ranges. It also answers the question of how to describe successive multi-photon scattering. In addition our formalism provides a complete framework for dealing with single and all multi-partite errors that can occur in the propagation, providing the basis for modeling future dedicated experiments that will then have applications in medicine, such as reducing errors in PET imaging or exploring possibilities for quantum-based diagnostic indicators. [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]

A study of the dead layer thickness and quenching factor of a plastic scintillator for use in ultracold neutron (UCN) experiments is described. Alpha spectroscopy was used to determine the thickness of a thin surface dead layer to be 630 ± 110 nm. The relative light outputs from the decay of 241Am and Compton scattering of electrons were used to extract Birks' law coefficient, yielding a kB value of 0.087 ± 0.003 mm/MeV, consistent with some previous reports for other polystyrene-based scintillators. The results from these measurements are incorporated into the simulation to show that an energy threshold of (∼9 keV) can be achieved for the UCNProBe experiment. This low threshold enables high beta particle detection efficiency and the indirect measurement of UCN. The ability to make the scintillator deuterated, accompanied by its relatively thin dead layer, gives rise to unique applications in a wide range of UCN experiments, where it can be used to trap UCN and detect charged particles in situ. [ABSTRACT FROM AUTHOR]

The soft X-ray excess in the spectra of active galactic nuclei is characterized by similar electron temperatures of 0.1–0.3 keV and similar photon indices around 2.2–3, if fitted with inverse Comptonization. It remains a puzzle why both values are not sensitive to the black hole mass nor the accretion rate. Supposing that the scattering-dominated surface layer of an accretion disk can act as a warm corona, we construct a vertical one-zone model to understand what determines its temperature. By solving the equations of (1) the condition for the effective optical depth, (2) the energy balance, and (3) the dominance of the Compton cooling over the bound–free cooling, we could reproduce the basic observational features of the soft excess, provided that anomalous heating (excess heating other than what is expected by local energy dissipation) takes place in the warm corona in agreement with similar studies done so far. The similar temperatures can be understood, since both the anomalous heating and Compton cooling rates are proportional to the dissipation rate of the accretion energy, while similar photon indices are a natural consequence of the fact that observed photons are finally emitted from the layer of Compton y ∼ 1. The soft excess is not observed in black hole binaries, since disk temperatures are too high for the Compton scattering to work as cooling. The derived temperatures are somewhat of an underestimation, however. This may indicate a necessity of multi-zone corona structure. The stability of the warm corona and its consequences are briefly discussed. [ABSTRACT FROM AUTHOR]

AbstractPrompt gamma-ray polarization is a practical method for detecting highly enriched uranium (HEU) in concealed sources. It also provides information on their geometry, magnetic fields, and radiation mechanisms. However, prompt gamma-ray polarization measurements have rarely been applied in nuclear nonproliferation areas to detect HEU. In this study, the feasibility of detecting the characteristic energy peak of 186 keV, which is associated with the asymmetry of the activation mechanism and the detection of energy-dependent polarization from concealed HEU sources, was evaluated using the Compton scattering approach. A Monte Carlo N-particle transport code simulation was used to realize the activation mechanism of HEU via two 1.4-mm strips of converter material [i.e., cesium lead tribromide (CsPbBr3)], transported by secondary scattered gamma rays during the three-stage process of Compton scattering, polarization, and detection.This paper presents the mathematical model, the physics of Compton scattering, and the polarization mechanism for the detection technique. In this case, the physics is relevant to both processes in which the emitted secondary scattered gamma rays undergo initial orthogonal polarization. Specifically, to meet the objective of testing the technical protocol for the enhanced detection of energy peaks associated with HEU, particularly 186 keV, simulations were conducted to quantify the HEU volume and neutron source strength in the MCNP data card to perform error analysis. The detector system had the potential to acquire good resolved photopeak with a 4.5% relative error or less, with a 1 Ci source activity, and a peak-to-background ratio of 1.15. This resolution took 163 s for high-purity germanium detection, which is comparable to current methods used for material detection placed within 100 to 900 s to completion. The small error difference was due to the attributes of the phenomenal enhancement properties of cesium tribromide and polarimetry. The identified photo peaks included K-shell X-rays from 235U, 61 keV from fission, 511-keV annihilation, and the peak of interest at 186 keV.The result from spectral analyses showed clear signatures related to pure and adulterated HEU. HEU detection with the low neutron yield and the easiness of shielding the yield of the HEU sample showed that the HEU characterization was feasible when shielded, with the highest success rate under both enhancement approaches. The optimization and scale-up of this technique are expected to enhance its applications in a large-scale HEU detection design. [ABSTRACT FROM AUTHOR]

The radiation shielding parameters such as effective atomic number, effective electron density, mean free path (MFP), half value layer (HVL) and tenth value layer (TVL) were calculated experimentally and theoretically for Boron Carbide(BC4), Boron nitride (BN), Boric acid (H3BO3), Iron boride (Fe2B), Lanthanum borate (BLaO3), Sodium borohydride (NaBH4), Borax (Na2H20B4O17), Titanium diboride (TiB2), and Zirconium diboride (ZrB2) compounds. In experimental measurements, the compounds were irradiated by 137Ba, 152Eu and 241Am radioactive gamma-ray sources. The theoretical results obtained with the help of the WinXCom computer program were compared with the experimental results and they were found to be in good agreement. Moreover, energy absorption buildup factor (EABF) and exposure buildup factor (EBF) values were calculated for compounds using the geometric progression (G.P.) fitting formula for the energy range of 0.015–15 MeV and penetration depth up to 40 mfp (mean free path). Buildup factors (EABF, EBF) increased with increasing penetration depth. In general, the buildup factors for all compounds formed a Gaussian curve and had the highest values in the energy range dominated by Compton scattering. As a result of the findings obtained in the study, it was seen that Lanthanum borate gave the best results in radiation shielding. [ABSTRACT FROM AUTHOR]

We present a phenomenological framework based on the MIT bag model to estimate the pressure experienced by quarks and gluons inside nucleons. This is accomplished by implementing non-extensive Tsallis statistics for the two-component system. In this model of hadrons, the strong interaction generates correlations effectively described by the q-Tsallis parameter. The resulting hadron pressure exhibits general agreement with recent calculations derived from Lattice QCD. Additionally, we compared this pressure with data extracted from deep virtual Compton scattering experiments and gravitational form factor analyses. The extended bag model provides an alternative interpretation of bag pressure in terms of the q-Tsallis parameter. Consequently, the MIT bag model can be expressed without requiring the inclusion of the bag pressure parameter. [ABSTRACT FROM AUTHOR]

The polarization of recoil photon ( γ ′ ) in the nonlinear Compton process e + L → → γ → ′ + e ′ in the interaction of a relativistic electron with a linearly polarized laser beam ( L → ) is studied within the Furry picture in the lowest order, tree-level S matrix element. In particular, we consider the asymmetry of differential cross sections A for two independent axes describing the Compton process equal to the intrinsic spin variable ξ 3 f that determines the polarization properties of γ ′ . The sign and absolute value of the asymmetry determine the direction and degree of γ ′ polarization. We have analyzed the process in a wide range of laser intensity that covers existing and future experiments. Our results provide additional knowledge for studying nonlinear multi-photon effects in quantum electrodynamics and can be used in planning experiments at envisaged laser facilities. [ABSTRACT FROM AUTHOR]

We present a systematic study demonstrating the impact of lattice QCD data on the extraction of generalised parton distributions (GPDs). For this purpose, we use a previously developed modelling of GPDs based on machine learning techniques fulfilling the theoretical requirements of polynomiality, a form of positivity constraint and known reduction limits. A special care is given to estimate the uncertainty stemming from the ill-posed character of the connection between GPDs and the experimental processes usually considered to constrain them, like deeply virtual Compton scattering (DVCS). Moke lattice QCD data inputs are included in a Bayesian framework to a prior model based on an Artificial Neural Network. This prior model is fitted to reproduce the most experimentally accessible information of a phenomenological extraction by Goloskokov and Kroll. We highlight the impact of the precision, correlation and kinematic coverage of lattice data on GPD extraction at moderate ξ which has only been brushed in the literature so far, paving the way for a joint extraction of GPDs. [ABSTRACT FROM AUTHOR]

Gamma-ray bursts (GRBs) comprise short, bright, energetic flashes of emission from extragalactic sources followed by a longer afterglow phase of decreased brightness. Recent discoveries of very high energy (VHE, ≳100 GeV) afterglow emission from GRB 180720B and GRB 190829A by the High Energy Stereoscopic System have raised questions regarding the emission mechanism responsible. We interpret this observed late-time emission to be the result of inverse Compton emission of ultrarelativistic electrons in the GRB blast wave in an external radiation field, i.e. external Compton (EC), considering both the wind and interstellar medium scenarios. We present predictions of multiwavelength light curves and energy spectra, ranging from optical to VHE, and include the synchrotron and synchrotron self-Compton (SSC) radiation mechanisms as well. We corrected the EC and SSC models for the gamma-ray attenuation by absorption of photons through their interaction with the extragalactic background light. We compared our results to multiwavelength data and found that EC gives a satisfactory fit for a given set of fixed model parameters for GRB 180720B, whereas SSC results in a better fit for GRB 190829A. For both GRBs, a wind environment is preferred over constant-density interstellar medium, and the cosmic microwave background as the external radiation field. However, with more data and an effective optimization tool we can find a more robust fit of the model, implying better constraints on the GRB environment and the particle energy requirements for the emission observed at late times. This has consequences for future observations of GRBs at these extreme energies. [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]

The structure of a compact X-ray source based on inverse Compton scattering and the beam dynamics in the linac and the storage ring is considered. The features of collective effects in the storage rings of such installations are studied in compaаrison with fourth-generation SR sources. The thresholds of longitudinal microwave instability and transverse instability of coupled modes are calculated. [ABSTRACT FROM AUTHOR]

Low-luminosity active galactic nuclei are strong sources of X-ray emission produced by Compton scattering originating from the accretion flows surrounding their supermassive black holes. The shape and energy of the resulting spectrum depend on the shape of the underlying electron distribution function (DF). In this work, we present an extended version of the grmonty code, called κmonty. The grmonty code previously only included a thermal Maxwell–Jütner electron DF. We extend the grmonty code with non-thermal electron DFs, namely the κ and power-law DFs, implement Cartesian Kerr–Schild coordinates, accelerate the code with mpi , and couple the code to the non-uniform adaptive mesh refinement grid data from the general relativistic magnetohydrodynamics code bhac. For the Compton scattering process, we derive two sampling kernels for both DFs. Finally, we present a series of code tests to verify the accuracy of our schemes. The implementation of non-thermal DFs opens the possibility of studying the effect of non-thermal emission on previously developed black hole accretion models. [ABSTRACT FROM AUTHOR]

Compton profiles (CPs) of TM2O3 (TM = Ti, V and Cr) have been measured using 100 mCi 241Am Compton spectrometer. The experimental momentum densities have been used to check the applicability of exchange-correlation energies using pure and hybrid density functional theory (DFT). Present ab-initio computations have been accomplished using the texture of Gaussian orbitals within linear combination of atomic orbitals (LCAO) scheme. Based on experimental and theoretical CPs, hybrid DFT schemes namely B3LYP and PBESOL0 have shown better performance than pure DFT (within local density and generalized gradient approximation), whereas the best agreement (through χ2 fitting of goodness) is obtained for B3LYP prescriptions. Besides Compton spectroscopy, the spin-up (↑) energy bands and density of states (DOS) have confirmed the metallic nature of all three compounds, whereas the spin-down (↓) energy bands and DOS for Ti2O3 and V2O3 have shown a peculiar semiconducting behaviour leading to their very peculiar half-metallic character. Further, higher values of charge transfer from all the 3d transition elements to O atoms, as witnessed using Mulliken's population analysis, show a dominancy of ionic nature in these oxides. Equally normalized CPs of these oxides show that the 3d electrons in oxide environment are delocalized (in real space) in the ascending sequence Cr→V→Ti, which is in contrast to their elemental-free atom environment. [ABSTRACT FROM AUTHOR]

Unitarity and the optical theorem are used to derive the reduced density matrices of Compton scattering in the presence of a witness particle. Two photons are initially entangled wherein one photon participates in Compton scattering, while the other is a witness, i.e., does not interact with the electron. Unitarity is shown to require that the entanglement entropy of the witness photon does not change after its entangled partner undergoes scattering. The final mutual information of the electron's and witness particle's polarizations is shown to be nonzero for low-energy Compton scattering. This indicates that the two particles became correlated in spite of no direct interaction. Assuming an initial maximally entangled state, the change in entanglement entropy of the scattered photon's polarization is calculated in terms of Stokes parameters. A common ratio of areas occurs in the final reduced density matrix elements, von Neumann entropies, Stokes parameter, and mutual information. This common ratio consists of the Thomson scattering cross-section and an accessible regularized scattering area. [ABSTRACT FROM AUTHOR]

We revisit the next-to-leading order (NLO) perturbative QCD corrections for the deeply virtual meson production (DVMP) process, exploring its phenomenology both in isolation and in a multichannel fit combined with deeply virtual Compton scattering (DVCS). Our approach involves the conformal partial wave (CPaW) formalism, which allows for the straightforward inclusion of higher-order contributions and evolutionary effects. Our findings indicate that a description of the longitudinal component of the vector meson DVMP cross-section at high energies is achievable only at NLO within the standard collinear approach. Furthermore, we demonstrate a simultaneous description of DIS, DVCS, and DVMP processes, providing insights into the proton structure described at NLO by unique universal generalized parton distribution (GPD) functions. [ABSTRACT FROM AUTHOR]

Multi-radionuclide in vivo imaging with submillimetre resolution can be a potent tool for biomedical research. While high-resolution radionuclide imaging faces challenges in sensitivity, multi-radionuclide imaging encounters difficulty due to radiation contamination, stemming from crosstalk between radionuclides and Compton scattering. Addressing these challenges simultaneously is imperative for multi-radionuclide high-resolution imaging. To tackle this, we developed a high-spatial-resolution and high-energy-resolution small animal single-photon emission computed tomography (SPECT) scanner, named CdTe-DSD SPECT-I. We first assessed the feasibility of multi-tracer SPECT imaging of submillimetre targets. Using the CdTe-DSD SPECT-I, we performed SPECT imaging of submillimetre zeolite spheres absorbed with 125I- and subsequently imaged 125I-accumulated spheroids of 200–400 µm in size within an hour, achieving clear and quantitative images. Furthermore, dual-radionuclide phantom imaging revealed a distinct image of the submillimetre sphere absorbed with 125I- immersed in a 99mTc-pertechnetate solution, and provided a fair quantification of each radionuclide. Lastly, in vivo imaging was conducted on a cancer-bearing mouse with lymph node micro-metastasis using dual-tracers. The results displayed dual-tracer images of lymph tract by 99mTc-phytic acid and the submillimetre metastatic lesion by 125I-, shown to align with the immunofluorescence image. [ABSTRACT FROM AUTHOR]

The research aims to study the primary interaction between gamma radiation in CeBr3 crystal. The analysis of mass attenuation coefficient (MAC), effective atomic number (Zeff), electron density (Neff), mean free path (MFP), and energy absorption buildup factor (EABF) was evaluated using the using the WinXCom software. Also, the interaction with charged particles as the total mass stopping power (TMSP), projected range (PR) of proton ( H 1 1 ) and alpha ( H 2 4 e ) particles were evaluated by SRIM programming. The results found that the MAC depends on the energy ranges, the photoelectric effect is the main interaction at low energy ranges, Compton scattering phenomena illustrate and evidents at intermediate energy ranges, and pair production characteristics dominate over on 1.022 MeV in high energy ranges. Moreover, absorption edges appear on energy's discontinuity at low energy. The Zeff and Neff show similar trends and correspond to the energy ranges. The MFP of the CeBr3 compared with some standard scintillators such as NaI and BGO crystal and found that the BGO responds to faster interaction than CeBr3 and NaI crystals. The EABF shows scattering energies followed by atomic equivalent (Zeq), and they also increase with increasing penetration depth (mfp). The TMSP and PR depend on charged particles, density, and the unit path distance of a material. [ABSTRACT FROM AUTHOR]

Gamma-ray bursts (GRBs) are the phenomena of rapid energy release of enormous power associated with the collapse or merging of stars. As a result of internal processes, populations of nonthermal accelerated particles radiating in a wide energy range are formed in them. A number of observations have shown that photons with energies up to tens of TeV are detected from some GRBs. However, due to the great energy losses of radiating particles, the explanation of this high-energy radiation in terms of standard radiation mechanisms runs into great difficulties. In this paper, based on the model of adiabatic expansion for the GRB afterglow phase, we investigate the influence of magnetic inhomogeneities on the spectra within the electron and proton synchrotron radiation mechanism by taking into account the Compton scattering of synchrotron photons. We show that the magnetic inhomogeneity effect can increase the maximum energies of the synchrotron radiation from electrons and protons several fold without affecting the maximum energies of the Compton photons being produced in the Klein–Nishina regime. [ABSTRACT FROM AUTHOR]

The short wavelength operation of free-electron laser (FEL) oscillators is limited by the availability of high-reflectivity, thermally stable, and radiation-resistant FEL mirrors in the vacuum UV (VUV) wavelength. We report our recent work to extend the shortest lasing wavelength of the oscillator FEL to 168.6 nm using a storage ring FEL. This progress has been made possible by developing a new FEL configuration with substantially reduced undulator harmonic radiation on the FEL mirror, a thermally stable FEL optical cavity, and a new type of high-reflectivity fluoride-based multilayer coating with a protective capping layer. Using these fluoride-based mirrors, we have demonstrated storage ring FEL lasing from 168.6 to 179.7 nm with excellent beam stability. Employing this VUV FEL in Compton scattering, we have produced the first 120 MeV gamma rays at the High Intensity Gamma-ray Source (HIGS). Operating the HIGS in this new high-energy region will create many new opportunities for photonuclear physics research, in particular, the low-energy quantum chromodynamics research. [ABSTRACT FROM AUTHOR]

Radiation hydrodynamical equations with Compton scattering are presented in a convenient way; equations are available in the subrelativistic regime of |$k_{\rm B}T/(m_{\rm e}c^2) \lesssim 0.1$|⁠ , |$h\nu /(m_{\rm e}c^2) \lesssim 0.1$| (or |$k_{\rm B}T_{\rm rad}/(m_{\rm e}c^2) \lesssim 0.1$|⁠), and |$v/c \lesssim 0.1$|⁠ , where T is the electron temperature, ν the photon frequency, T rad the photon temperature, and v the fluid bulk velocity. Several basic concepts and radiation hydrodynamical phenomena under Compton scattering are briefly discussed; e.g. electron-scattering opacity and the Eddington luminosity, optical depth and a static atmosphere, the photon trapping radius, the magic terminal speed, the pseudo-photosphere of radiative winds, the explicit form of basic equations for steady flows, radiation acoustic wave, and so on. [ABSTRACT FROM AUTHOR]

All-optical Compton sources combine laser-wakefield accelerators and intense scattering pulses to generate ultrashort bursts of backscattered radiation. The scattering pulse plays the role of a small-period undulator (${\sim }1\,\mathrm {\mu }{\rm m}$) in which relativistic electrons oscillate and emit X-ray radiation. To date, most of the working laser-plasma accelerators operate preferably at energies of a few hundreds of megaelectronvolts and the Compton sources developed so far produce radiation in the range from hundreds of kiloelectronvolts to a few megaelectronvolts. However, for such applications as medical imaging and tomography the relevant energy range is 10–100 keV. In this article, we discuss different scattering geometries for the generation of X-rays in this range. Through numerical simulations, we study the influence of electron beam parameters on the backscattered photons. We find that the spectral bandwidth remains constant for beams of the same emittance regardless of the scattering geometry. A shallow interaction angle of $30^{\circ }$ or less seems particularly promising for imaging applications given parameters of existing laser-plasma accelerators. Finally, we discuss the influence of the radiation properties for potential applications in medical imaging and non-destructive testing. [ABSTRACT FROM AUTHOR]

Accurate modeling is necessary to support precision experiments investigating strong-field QED phenomena. This modeling is particularly challenging in the transition between the perturbative and nonperturbative regimes, where the normalized laser amplitude a0 is comparable to unity and wavelength-scale interference is significant. Here, we describe how to simulate nonlinear Compton scattering, Breit–Wheeler pair creation, and trident pair creation in this regime, using the Monte Carlo particle-tracking code Ptarmigan. This code simulates collisions between high-intensity lasers and beams of electrons or γ rays, primarily in the framework of the locally monochromatic approximation. We benchmark our simulation results against full QED calculations for pulsed plane waves and show that they are accurate at the level of a few per cent, across the full range of particle energies and laser intensities. This work extends our previous results to linearly polarized lasers and arbitrary polarized γ rays. [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]

Spin-polarized positron beams have widely been utilized in applications ranging from fundamental physical studies to material processing. Preparing highly polarized positron beams for accurate probing is a long-standing issue. Here, we put forward a method to produce ultra-relativistic polarized positrons with unprecedented purity in a femtosecond timescale employing a few-PW circularly polarized laser pulse. The fully spin-resolved QED Monte Carlo method is used for simulating the two successive QED processes during the interaction, i.e., nonlinear Compton scattering and nonlinear Breit–Wheeler pair production. As the photons emitted in a circularly polarized laser field are symmetrically polarized, the polarization of the intermediate gamma photon beam averages out to zero, which is advantageous for improving the polarization of positrons. Meanwhile, the moderate laser intensity suppresses the depolarization of the new-born positrons induced by radiation reaction effect. As a result, the polarization of the positrons can reach up to ≳ 90%, the highest among the laser-driven polarization schemes conceived hitherto. Furthermore, our method relaxes the requirement on laser intensity to few-PW level, offering a promising way of preparing polarized positrons with current-generation laser facilities. [ABSTRACT FROM AUTHOR]

The infiltration of immune cells into sites of inflammation is one key feature of immune mediated inflammatory diseases. A detailed assessment of the in vivo dynamics of relevant cell subtypes could booster the understanding of this disease and the development of novel therapies. We show in detail how advanced X-ray fluorescence imaging enables such quantitative in vivo cell tracking, offering solutions that could pave the way beyond what other imaging modalities provide today. The key for this achievement is a detailed study of the spectral background contribution from multiple Compton scattering in a mouse-scaled object when this is scanned with a monochromatic pencil X-ray beam from a synchrotron. Under optimal conditions, the detection sensitivity is sufficient for detecting local accumulations of the labelled immune cells, hence providing experimental demonstration of in vivo immune cell tracking in mice. [ABSTRACT FROM AUTHOR]

Hydrogen spillover is an elusive process, and its characterization, using experimental probes and ab initio modeling, poses a serious challenge. In this work, the nuclear quantum dynamics of hydrogen in a palladium-decorated cubic polymorph of tungsten oxide, Pd/cWO3, are characterized by the technique of neutron Compton scattering augmented by ab initio harmonic lattice modeling. The deeply penetrating nature of the neutron scattering process, the lack of spectroscopic selection rules, the inherent high sensitivity to hydrogen, the high energy and momentum resolution for hydrogen, and the mass selectivity of the technique render the neutron Compton scattering a very potent and unique tool for investigating the local dynamics of hydrogen species in bulk matrices. The total neutron Compton scattering response of hydrogen is described in terms of the hydrogen momentum distribution. The distribution is deconvoluted under the assumption of three pools of hydrogen with distinctly different nuclear quantum dynamical behavior: (i) hydrogen-terminated beta-palladium hydride, (ii) hydrogen in acid centers (OH+ groups) on the surface of the cubic phase of tungsten oxide, and (iii) quasi-free atomic hydrogen inside the saturated hydrogen bronze resulting from the spillover process. The ab initio modeling of lattice dynamics yields theoretical predictions for the values of the widths of proton momentum distributions in the first two hydrogen pools, which allows for obtaining the contribution and the width of the momentum distribution of the quasi-free atomic hydrogen resulting from the hydrogen spillover process. The analysis reveals that the local binding strength of the quasi-free hydrogen is characterized by the values of nuclear momentum distribution width, nuclear kinetic energy, and force constant of the underlying potential of the mean force close to those of free, unconstrained hydrogen atomic species in a gas of non-interacting particles described by the Maxwell–Boltzmann distribution. Moreover, this picture of the local dynamics of the quasi-free hydrogen is consistent with the proton polaron model of hydrogen-induced coloration of bulk hydrogenated WO3. [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]

Inspired by a dipole asymmetric template for the CMB temperature map in the primordial scalar fluctuations observed by Planck at a large scale, we examine the contribution of a similar template for power asymmetry in modifying the linear polarization pattern of CMB. Replacing un-modulated temperature fluctuation with dipolar modulated one in time evolution equations somehow breaks linear perturbation in the various components of the CMB map. This non-linearity allows deflecting CMB polarization in patterns that contain divergence-free components. The explicit expressions for the angular power spectra of the electric and magnetic-type parities of linear polarization are derived in the form of the line of sight integral solutions. Our results demonstrate that the electric-type polarization is modified and the magnetic-type polarization would be produced. Such imprints depend on the linear and square of the asymmetric amplitude for E- and B-modes power spectra, respectively. For the observed dipole template, the value of B polarization spectrum at the large scale ( ℓ ≲ 10 ) is almost equivalent to the power spectrum obtained from Compton scattering in the presence of tensor perturbation with tensor to scalar ratio about r ≃ 0.005 . [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]

The exclusive dilepton photoproduction in pp and pAu collisions at RHIC is investigated considering the contribution of the Bethe–Heitler (BH) and the timelike Compton scattering (TCS) processes. The TCS amplitude is estimated at next-to-leading-order of the strong running coupling constant α s and assuming the Goloskokov–Kroll model for the quark and gluon generalized parton distributions. The TCS differential cross section is estimated as well the contribution associated to the interference between the TCS and BH amplitudes. Predictions for the TCS, BH and interference contributions are presented considering the kinematical range covered by the RHIC detectors. [ABSTRACT FROM AUTHOR]

We estimate the impact of asymmetry measurements of Deeply Virtual Compton Scattering (DVCS) with transversely polarized proton beam taken at a future Electron Ion Collider in China (EicC) on the extraction of Compton Form Factors (CFFs). The CFFs extracted from an analysis based on artificial neural-network approach are reweighted by means of pseudo-data generated in the expected kinematic region of EicC. We find a remarkable improvement in the extraction of CFF I m E , especially at the range of parton momentum fraction x ∼ 0.01, thus hinting for a future experimental probe of the parton orbital angular momentum. This work casts a glance at a practical implementation of Bayesian reweighting method on CFFs' impact study. [ABSTRACT FROM AUTHOR]

We introduce a novel bootstrap method for heavy-mass effective field theory classical Compton scattering amplitudes involving two massless particles and two arbitrary-spin infinite-mass limit particles. Using a suitable ansatz, we deduce new and explicit classical spin results for gluon four and five-point infinite mass processes that exhibit a certain exponentiated three-point tree-level factorizations and feature no spurious poles. We discuss the generalization of our bootstrap to higher multiplicities and summarize future potential applications. [ABSTRACT FROM AUTHOR]

We present analyses of an Intermediate Polar, IGR J15094-6649, based on the archival optical data obtained from the Transiting Exoplanet Survey Satellite (TESS) and X-ray data obtained from the Suzaku, NuSTAR , and Neil Gehrels Swift Observatory (Swift). Present analysis confirms and refines the previously reported spin period of IGR J15094-6649 as 809.49584 ± 0.00075 s. Clear evidence of a beat period of 841.67376 ± 0.00082 s is found during the long-term TESS optical observations, which was not evident in the earlier studies. The dominance of X-ray and optical spin pulse unveils the disc-fed dominance accretion, however, the presence of an additional beat frequency indicates that part of the accreting material also flows along the magnetic field lines. The energy-dependent spin pulsations in the low (<10 keV) energy band are due to the photoelectric absorption in the accretion flow. However, the complex absorbers may be responsible to produce low amplitude spin modulations via Compton scattering in the hard (>10 keV) energy band and indicate that the height of the X-ray emitting region may be negligible. The observed double-humped X-ray profiles with a pronounced dip are indicative of the photoelectric absorption in the intervening accretion stream. Analysis of the X-ray spectra reveals the complexity of the X-ray emission, being composed of multitemperature plasma components with a soft excess, reflection, and suffers from strong absorption. [ABSTRACT FROM AUTHOR]