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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]

In this paper, we present the generalities of the Compton interaction process; we analyse the different paradigms of Inverse Compton Sources, implemented or in commissioning phase at various facilities, or proposed as future projects. We present an overview of the state of the art, with a discussion of the most demanding challenges. [ABSTRACT FROM AUTHOR]

One of the most noteworthy aspects of computed tomography (CT) based on the nuclear resonance fluorescence (NRF) transmission method is the isotope selectivity that makes it possible to discern an isotope of interest from other isotopes within a sample. We experimentally obtained a three-dimensional (3D) isotope-selective CT image based on the NRF transmission method (3D NRF-CT) for the enriched lead isotope distribution of 208Pb in a cylindrical holder in a previous study. The cylindrical holder's diameter and height are 25 mm and 20 mm, respectively. The NRF-CT imaging technique requires a considerable data accumulation time. It took 48 h to obtain an image with a resolution of 4 mm/pixel in the horizontal plane and 8 mm/pixel in the vertical plane using a laser Compton scattering (LCS) gamma-ray beam with a beam size of 2 mm and a flux density of 10 photons/s/eV. Improving the NRF-CT image resolution with the existing hardware is challenging. Therefore, we proposed an alternative method to improve the NRF-CT image resolution using the fusion visualization (FV) technique by combining the NRF-CT image including isotopic information with a gamma-CT image, which provides better pixel resolution. The 3D gamma-CT image for the same sample was measured at the same beamline BL1U in the ultraviolet synchrotron orbital radiation-III (UVSOR-III) synchrotron radiation facility at the Institute of Molecular Science at the National Institutes of Natural Sciences in Japan under similar experimental conditions except for the LCS gamma-ray beam flux and beam size. Obtaining a 3D gamma-CT image with a resolution of 1 mm/pixel took 5 h using an LCS gamma-ray beam with a beam size of 1 mm and a flux density of 0.7 photons/s/eV. The data processing of the FV technique has been developed, and the 3D NRF-CT image quality was improved. [ABSTRACT FROM AUTHOR]

• First-ever magnetic Compton profiles (MCPs) of non-stoichiometric Ni 0.9-x Pr x Fe 2.1 O 4 inverse spinel ferrites. • Decomposed experimental MCPs into constituent profiles of Ni, Fe, Pr-4f and diffuse electrons. • Validated MCP based total and site-specific spin moments using FP-LAPW calculations. • Explored role of orbital magnetic moments using MCP data and magnetization data. • Revealed effect of Pr-4f states in amending the spin moments and electronic properties. Magnetic Compton profiles of 5 % and 15 % Pr-doped non-stoichiometric NiFe 2 O 4 have been measured using synchrotron radiations of energy 182.65 keV at SPring-8, Japan. An analysis of MCPs measured at 6 and 300 K show that the total spin moment decreases with increasing temperature and Pr concentration in Ni 0.9-x Pr x Fe 2.1 O 4 which is consistent with the magnetic moment (spin + orbital) as observed from magnetization measurements data. Spin moments at different sites are deduced using decomposition of MCPs in the elemental profiles of Ni, Pr-4f, Fe and diffused electrons. Spin moments at Ni-site have been found to play crucial role in emergence of absolute spin moments. Spin moments at Pr-site is aligned antiparallel to that of Ni and Fe sites. The orbital magnetic moment is also deduced from the subtraction of MCP based spin moments from the magnetization data. Theoretical FP-LAPW based total and atom specific spin moments are found in consonance with the MCP based data. Total and spin projected density of states are also computed using the FP-LAPW method to validate role of Pr-4f and Fe-3d (O h) states in amending the total magnetic moment with Pr concentration. The M−H based saturation magnetization derived at 6 and 300 K temperature show that the saturation magnetic moments reduce from 2.21 → 2.05 μ B /f.u. at 6 K and 2.10 → 1.98 μ B /f.u. at 300 K with increase in Pr concentration from 5 % → 15 %. On the basis of hysteresis curve and coercive force, both the doped compounds show soft magnetism. [ABSTRACT FROM AUTHOR]

• Measured spin momentum densities for Ni/Co doped LCMO using synchrotron radiations. • Elaborated peculiarities of magnetism using experimental MCPs and DFT computations. • Revealed mixed valence states of Mn and its ferromagnetic interaction with Ni and Co. • Explored Z-in and Z-out JT distortion in LCMO and after Ni and Co doping. • Disseminated guidelines for interpretation of MCP data using ab-initio computations. Magnetic Compton profiles (MCPs) of La 0.7 Ca 0.3 Mn 0.95 (Ni/Co) 0.05 O 3 between 8 and 250 K have been measured using high energy inelastic scattering at SPring-8, Japan. For a quantitative analysis on amendment of magnetic properties, temperature-dependent experimental MCPs are decomposed into constituent profiles related to Mn, Ni/Co and itinerant (diffuse) electrons. Decomposed profiles unambiguously show that Mn-3d electrons are ferromagnetically coupled with Ni/Co ions while itinerant electrons are linked anti-ferromagnetically with Mn-3d and Ni/Co-3d electrons. An annotation of MCP and VSM data depicts that the orbital magnetic moments are anti-ferromagnetically coupled to total spin moments. Variation in magnetic response in undoped and Ni/Co doped perovskites is devoted to formation of mixed valence states of Mn atom. The spin contribution at different sites are found to be in tune with present density functional theory (DFT) based calculations which are thoroughly analyzed on the basis of changes in the e g and t 2g states of Mn, Ni/Co caused by Jahn-Teller distortion. Present MCP data and DFT calculations set guidelines to probe the reliable origin to examine magnetic response and half-metallic properties of such manganites. [ABSTRACT FROM AUTHOR]

Mammary neoplasms are the most common in female dogs, with high malignancy rates. Despite sharing many similarities with human breast tissues, the prevalence of this type of cancer in dogs are nearly three times higher. Taking that into account, this study aims to present preliminary results about chemical and structural changes occurring in samples of canine breast tumors. For this, we analyzed seven samples including normal, benign and malignant tissues, using micro X-ray fluorescence (μ -XRF) and Compton scattering technique. Our goal was to respectively map the spatial distribution of Fe, Cu and Zn and to determine the electron densities in selected regions of the samples. Results showed that Cu and Zn distributions were spatially correlated in normal tissues, with lower intensities in adipose regions and higher in the fibrous ones. Regarding benign neoplasms, both samples exhibited an increase in Cu intensity over the tumor area, however in different proportions. For the malignant ones, the presence of Fe was observed mostly in the tumor-adjacent regions. The electron density values obtained allowed to differentiate tissue structures, with generally higher density in tumorous regions and lower in adipose tissues. • Health and tumoral canine breast samples were analyzed using synchrotron radiation. • Micro-XRF and Compton scattering techniques were combined. • Micro-XRF provided the spatial distribution of Fe, Cu and Zn in the samples. • Compton scattering was sensitive to variations of electron densities in the samples. [ABSTRACT FROM AUTHOR]

MicroBeam Radiosurgery (MBRS, also referred to as Microbeam Radiation Therapy, MRT) is a potential clinical technique for the treatment of solid tumors. MBRS utilizes a series of narrow 30 to 50 μ m beams of ultra-high, lethal dose synchrotron x-ray radiation (peaks) separated by relatively wide spaces of no radiation (valleys) with spacings of 200 to 400 μ m center-to-center. It has been observed that healthy small animal tissue, including neurologic tissue (brain and spinal cord), can recover quickly, but solid tumors take a prolonged time of many months to regrow. This vast difference in recovery period is the basis for the therapeutic effect of MBRS on tumors. The interactions of X rays and tissue cells in alignment with the microbeams cause some deposited dose to be delivered to the tissue between the peak region of the microbeams and spill into the valley regions. It is generally believed that the dose delivered between the microbeam peak regions must be maintained at a low level to maximize the efficacy of MBRS. To date the most widely used criterion for the efficacy of MBRS is known as the Peak-to-Valley Dose Ratio (PVDR). This ratio depends on the geometry of the system along with the X-ray spectra. As most of the experimental work to date has used polychromatic microbeams of X rays, the PVDR will change with the energy range and spectrum. We are reporting novel investigations and present data suggesting considerations additional to the PVDR are needed for the design of a human clinical facility. In this paper we studied X-ray interactions in simulated human biologic material (Water - H 2 O) using the MCNP6 radiation transport computer code. The new slit geometry dependent information includes: (1) rounding of peak shape; (2) decrease of the maximum peak height with decreasing peak slit width; (3) qualitative and quantitative changes to the "skirt" radiation dose delivered in the valley regions adjacent to the peak regions. All these effects were highly dependent on incident X-ray energy because of the transition of the dominant X-ray interaction from the photo-electric effect to atomic Compton scattering with increasing energy in the 50 to 300 keV range. Changes in the radiation dose distributions, as a function of X-ray energy, delivered to both the peak and valley regions after the X-ray interactions were investigated in detail. Insights from understanding how the dose is delivered in the valley regions have implications for the calculations of the clinical radiation dose planning. Accurate dose distribution calculations are necessary in human clinical treatment since it is anticipated that most patients will have received prior radiation therapy treatments that need to be considered in microbeam dose planning so that radiation side-effects and toxicity are accounted for and minimized. This work suggests an X-ray energy range of 130–250 keV is the most appropriate range for a human clinical facility. Using the results of this work, the authors suggest that the PVDR may not be the only criteria one should consider for determining the energy range needed for a human clinical facility; analysis of the data presented demonstrates the benefit of also using the full width at 10% maximum of the distribution. [ABSTRACT FROM AUTHOR]

The uncertainty of the energy measurement of the electron beam on circular electron positron collider (CEPC) must be smaller than 10 MeV to make sure the accurate measurement of the mass of the Higgs boson. In order to simplify the energy measurement system, a new method is proposed by fitting the Compton edge of the energy distribution of the gamma ray from a microwave–electron Compton scattering. With our method, the uncertainty of the energy measurement is 6 MeV for the electron energy of 120 GeV in the Higgs mode. In this system, the energy resolution of the gamma detection needs to reach 1 0 − 4 . Therefore, only the high-purity germanium (HPGe) detector can meet the critical requirement. In a head-on collision mode, the initial photons should be microwave photons with the wavelength of 3.04 centimeters. A cylindrical resonant cavity with selected T M 010 mode is used to transmit microwaves. After the microwave–electron Compton backscattering, the scattered photons and the synchrotron-radiation background transmit a shielding structure and then are detected by a HPGe detector at the end of the beam line of the synchrotron-radiation applications. The hole radius in the side wall of the cavity is about 1. 5 mm to allow the electron beam passing through. The results of the computer simulation technology (CST) software shows that the influence of the hole radius on the cavity field is negligible. The change of the resonance frequency can be easily corrected by fine-tuning the cavity size. [ABSTRACT FROM AUTHOR]