Showing papers on "Synchrotron radiation published in 2019"

Teraelectronvolt emission from the γ-ray burst GRB 190114C

Abstract: Long-duration γ-ray bursts (GRBs) are the most luminous sources of electromagnetic radiation known in the Universe. They arise from outflows of plasma with velocities near the speed of light that are ejected by newly formed neutron stars or black holes (of stellar mass) at cosmological distances 1$^{,}$2 . Prompt flashes of megaelectronvolt-energy γ-rays are followed by a longer-lasting afterglow emission in a wide range of energies (from radio waves to gigaelectronvolt γ-rays), which originates from synchrotron radiation generated by energetic electrons in the accompanying shock waves 3$^{,}$4 . Although emission of γ-rays at even higher (teraelectronvolt) energies by other radiation mechanisms has been theoretically predicted 5$^{–}$8 , it has not been previously detected 7$^{,}$8 . Here we report observations of teraelectronvolt emission from the γ-ray burst GRB 190114C. γ-rays were observed in the energy range 0.2–1 teraelectronvolt from about one minute after the burst (at more than 50 standard deviations in the first 20 minutes), revealing a distinct emission component of the afterglow with power comparable to that of the synchrotron component. The observed similarity in the radiated power and temporal behaviour of the teraelectronvolt and X-ray bands points to processes such as inverse Compton upscattering as the mechanism of the teraelectronvolt emission 9$^{–}$11 . By contrast, processes such as synchrotron emission by ultrahigh-energy protons 10$^{,}$12$^{,}$13 are not favoured because of their low radiative efficiency. These results are anticipated to be a step towards a deeper understanding of the physics of GRBs and relativistic shock waves.

Observation of inverse Compton emission from a long γ-ray burst

Abstract: Long-duration γ-ray bursts (GRBs) originate from ultra-relativistic jets launched from the collapsing cores of dying massive stars. They are characterized by an initial phase of bright and highly variable radiation in the kiloelectronvolt-to-megaelectronvolt band, which is probably produced within the jet and lasts from milliseconds to minutes, known as the prompt emission1,2. Subsequently, the interaction of the jet with the surrounding medium generates shock waves that are responsible for the afterglow emission, which lasts from days to months and occurs over a broad energy range from the radio to the gigaelectronvolt bands1-6. The afterglow emission is generally well explained as synchrotron radiation emitted by electrons accelerated by the external shock7-9. Recently, intense long-lasting emission between 0.2 and 1 teraelectronvolts was observed from GRB 190114C10,11. Here we report multi-frequency observations of GRB 190114C, and study the evolution in time of the GRB emission across 17 orders of magnitude in energy, from 5 × 10-6 to 1012 electronvolts. We find that the broadband spectral energy distribution is double-peaked, with the teraelectronvolt emission constituting a distinct spectral component with power comparable to the synchrotron component. This component is associated with the afterglow and is satisfactorily explained by inverse Compton up-scattering of synchrotron photons by high-energy electrons. We find that the conditions required to account for the observed teraelectronvolt component are typical for GRBs, supporting the possibility that inverse Compton emission is commonly produced in GRBs.

X-Ray Free-Electron Lasers for the Structure and Dynamics of Macromolecules.

Abstract: X-ray free-electron lasers provide femtosecond-duration pulses of hard X-rays with a peak brightness approximately one billion times greater than is available at synchrotron radiation facilities. One motivation for the development of such X-ray sources was the proposal to obtain structures of macromolecules, macromolecular complexes, and virus particles, without the need for crystallization, through diffraction measurements of single noncrystalline objects. Initial explorations of this idea and of outrunning radiation damage with femtosecond pulses led to the development of serial crystallography and the ability to obtain high-resolution structures of small crystals without the need for cryogenic cooling. This technique allows the understanding of conformational dynamics and enzymatics and the resolution of intermediate states in reactions over timescales of 100 fs to minutes. The promise of more photons per atom recorded in a diffraction pattern than electrons per atom contributing to an electron micrograph may enable diffraction measurements of single molecules, although challenges remain.

Simulation of Interaction of Synchrotron Radiation Emission as a Function of the Beam Energy and Bohrium Nanoparticles Using 3D Finite Element Method (FEM) as an Optothermal Human Cancer Cells, Tissues and Tumors Treatment

Abstract: In the current study, thermoplasmonic characteristics of Bohrium nanoparticles with spherical, core–shell and rod shapes are investigated. In order to investigate these characteristics, interaction of synchrotron radiation emission as a function of the beam energy and Bohrium nanoparticles were simulated using 3D finite element method. Firstly, absorption and extinction cross sections were calculated. Then, increases in temperature due to synchrotron radiation emission as a function of the beam energy absorption were calculated in Bohrium nanoparticles by solving heat equation. The obtained results show that Bohrium nanorods are more appropriate option for using in optothermal human cancer cells, tissues and tumors treatment method.

Prompt optical emission as a signature of synchrotron radiation in gamma-ray bursts

Abstract: Information on the spectral shape of prompt emission in gamma-ray bursts (GRB) is mostly available only at energies ≳10 keV, where the main instruments for GRB detection are sensitive. The origin of this emission is still very uncertain because of the apparent inconsistency with synchrotron radiation, which is the most obvious candidate, and the resulting need for considering less straightforward scenarios. The inclusion of data down to soft X-rays (∼0.5 keV), which are available only in a small fraction of GRBs, has firmly established the common presence of a spectral break in the low-energy part of prompt spectra, and even more importantly, the consistency of the overall spectral shape with synchrotron radiation in the moderately fast-cooling regime, the low-energy break being identified with the cooling frequency. In this work we further extend the range of investigation down to the optical band. In particular, we test the synchrotron interpretation by directly fitting a theoretically derived synchrotron spectrum and making use of optical to gamma-ray data. Secondly, we test an alternative model that considers the presence of a black-body component at ∼keV energies, in addition to a non-thermal component that is responsible for the emission at the spectral peak (100 keV–1 MeV). We find that synchrotron radiation provides a good description of the broadband data, while models composed of a thermal and a non-thermal component require the introduction of a low-energy break in the non-thermal component in order to be consistent with optical observations. Motivated by the good quality of the synchrotron fits, we explore the physical parameter space of the emitting region. In a basic prompt emission scenario we find quite contrived solutions for the magnetic field strength (5 G ′ γ > 1016 cm). We discuss which assumptions of the basic model would need to be relaxed in order to achieve a more natural parameter space.

Modeling non-thermal emission from the jet-launching region of M 87 with adaptive mesh refinement

Abstract: Context. The galaxy M 87 harbors a kiloparsec-scale relativistic jet, whose origin coincides with a compact source thought to be a supermassive black hole. Observational millimeter very long baseline interferometry campaigns are capable of resolving the jet-launching region at the scale of the event horizon. In order to provide a context for interpreting these observations, realistic general-relativistic magnetohydrodynamical (GRMHD) models of the accretion flow are constructed.Aims. Electrons in the jet are responsible for the observed synchrotron radiation, which is emitted in frequencies ranging from radio to near-infrared (NIR) and optical. The characteristics of the emitted radiation depend on the shape of the electrons’ energy-distribution function (eDF). The dependency on the eDF is omitted in the modeling of the first Event Horizon Telescope results. In this work, we aim to model the M 87 spectral-energy distribution from radio up to optical frequencies using a thermal-relativistic Maxwell–Juttner distribution, as well as a relativistic κ -distribution function. The power-law index of the eDF is modeled based on sub-grid, particle-in-cell parametrizations for sub-relativistic reconnection.Methods. A GRMHD simulation in Cartesian–Kerr–Schild coordinates, using eight levels of adaptive mesh refinement (AMR), forms the basis of our model. To obtain spectra and images, the GRMHD data was post-processed with the ray-tracing code RAPTOR, which is capable of ray tracing through GRMHD simulation data that is stored in multi-level AMR grids. The resulting spectra and images maps are compared with observations.Results. We obtain radio spectra in both the thermal-jet and κ -jet models consistent with radio observations. Additionally, the κ -jet models also recover the NIR and optical emission. The images show a more extended structure at 43 GHz and 86 GHz and more compact emission at 228 GHz. The models recover the observed source sizes and core shifts and obtain a jet power of ≈1043 ergs s−1 . In the κ -jet models, both the accretion rates and jet powers are approximately two times lower than the thermal-jet model. The frequency cut-off observed at ν ≈ 1015 Hz is recovered when the accelerator size is 106 − 108 cm, this could potentially point to an upper limit for plasmoid sizes in the jet of M 87.

Comparison of synchrotron radiation and synchrocyclotron radiation performance in monitoring of human cancer cells, tissues and tumors

Abstract: Received: June 04, 2019; Accepted: July 03, 2019; Published: July 10, 2019 DNA/RNA hypermethylation and hypomethylation is hygroscope and can be mixed easily with human cancer cells, tissues and tumors and lots of organic components. Hydrate inhabitation, coolant, stabilizer, etc. are some applications of DNA/RNA hypermethylation and hypomethylation. DNA/RNA hypermethylation and hypomethylation are used widely in human cancer cells, tissues and tumors extraction sites as an anti–freezing substance. Therefore, it’s found in the effluent of human cancer cells, tissues and tumors refinery science. Besides, DNA/ RNA hypermethylation and hypomethylation are traced in the effluent of DNA/RNA hypermethylation and hypomethylation producing science. According to presence of DNA/RNA hypermethylation and hypomethylation in the monitoring of human cancer cells, tissues and tumors, the effect of presence of DNA/RNA hypermethylation and hypomethylation on a moving synchrotron radiation and synchrocyclotron radiation performance is investigated in this research. The experiments where designed for 200, 400, 600, 800 and 1000 (ppm) of DNA/RNA hypermethylated and hypomethylated’s concentrations. The hydraulic retention time was set 96 hours for the of synchrotron radiation and 48 hours for the synchrocyclotron radiation. The DNA/ RNA hypermethylated and hypomethylated removal percentage for the synchrotron radiation was measured 27.3%, 46.9% and 71.7% for different concentrations, respectively. This parameter was measured for the second system 54.6%, 68.3% and 79.4%, respectively. The study was carried out using synchrotron radiation and synchrocyclotron radiation performance in monitoring of human cancer cells, tissues and tumors, plus balanced macro nutrients and alkalinity. The DNA/RNA hypermethylated and hypomethylated was enriched with the macronutrients by adding some proteins as Nitrogen sources and nucleic acids as Phosphorus sources and in addition to different amount of DNA/RNA hypermethylated and hypomethylated concentration from 500 to 700 (ppm). The temperature and pH of the influent were set as 23 ± 3 C° and 7.0 ± 7, respectively (Figure 1) [1-364].

Soft X-ray spectroscopy with transition-edge sensors at Stanford Synchrotron Radiation Lightsource beamline 10-1.

Abstract: We present results obtained with a new soft X-ray spectrometer based on transition-edge sensors (TESs) composed of Mo/Cu bilayers coupled to bismuth absorbers. This spectrometer simultaneously provides excellent energy resolution, high detection efficiency, and broadband spectral coverage. The new spectrometer is optimized for incident X-ray energies below 2 keV. Each pixel serves as both a highly sensitive calorimeter and an X-ray absorber with near unity quantum efficiency. We have commissioned this 240-pixel TES spectrometer at the Stanford Synchrotron Radiation Lightsource beamline 10-1 (BL 10-1) and used it to probe the local electronic structure of sample materials with unprecedented sensitivity in the soft X-ray regime. As mounted, the TES spectrometer has a maximum detection solid angle of 2 × 10-3 sr. The energy resolution of all pixels combined is 1.5 eV full width at half maximum at 500 eV. We describe the performance of the TES spectrometer in terms of its energy resolution and count-rate capability and demonstrate its utility as a high throughput detector for synchrotron-based X-ray spectroscopy. Results from initial X-ray emission spectroscopy and resonant inelastic X-ray scattering experiments obtained with the spectrometer are presented.

Computational approach to interaction between synchrotron radiation emission as a function of the beam energy and ruthenium nanoparticles in human gum cancer cells, tissues and tumors treatment

Abstract: In recent decade, metallic nanoparticles have been widely interested due to their interesting optical characteristics [1-8]. Resonances of surface Plasmon in these nanoparticles lead to increase in synchrotron radiation emission as a function of the beam energy scattering and absorption in related frequency [9,10]. Synchrotron radiation emission as a function of the beam energy absorption and induced produced heat in nanoparticles has been considered as a side effect in plasmonic applications for a long time [11-15]. Recently, scientists find that thermoplasmonic characteristic can be used for various optothermal applications in cancer, nanoflows and photonic [16-22]. In optothermal human cancer cells, tissues and tumors treatment, the descendent laser light stimulate resonance of surface Plasmon of metallic nanoparticles and as a result of this process, the absorbed energy of descendent light converse to heat in nanoparticles [23-25]. The produced heat devastates tumor tissue adjacent to nanoparticles without any hurt to Abstract

Laser heating setup for diamond anvil cells for in situ synchrotron and in house high and ultra-high pressure studies

Abstract: The diamond anvil cell (DAC) technique combined with laser heating is one of the major methods for studying materials at high pressure and high temperature conditions. In this work, we present a transferable double-sided laser heating setup for DACs with in situ temperature determination. The setup allows precise heating of samples inside a DAC at pressures above 200 GPa and could be combined with synchrotron beamline equipment. It can be applied to X-ray diffraction and X-ray transmission microscopy experiments. In the setup, we use high-magnification and low working distance infinity corrected laser focusing objectives that enable us to decrease the size of the laser beam to less than 5 µm and achieve the maximum optical magnification of 320 times. All optical components of the setup were chosen to minimize chromatic and spatial aberrations for accurate in situ temperature determination by multiwavelength spectroscopy in the 570–830 nm spectral range. Flexible design of our setup allows simple interchange of laser sources and focusing optics for application in different types of studies. The setup was successfully tested in house and at the high-pressure diffraction beamline ID15B at the European Synchrotron Radiation Facility. We demonstrate an example of application of the setup for the high pressure–high temperature powder diffraction study of PdH and X-ray transmission microscopy of platinum at 22(1) GPa as a novel method of melting detection in DACs.

Hartree-fock Methods Analysis Protonated Rhodochrosite Crystal and Potential in the Elimination of Cancer Cells Through Synchrotron Radiation

Abstract: The rhodochrosite as crystal oscillator for being an alternative to those of quartz. The rhodochrosite (MnCO3) shows complete solid solution with siderite (FeCO3), and it may contain substantial amounts of Zn, Mg, Co, and Ca. There is no precedent in the literature on the treatment of tumor tissues by eliminating these affected tissues, using rhodocrosite crystals in tissue absorption and eliminating cancerous tissues by synchrotron radiation. The studies that are found are the research papers of this team. Through an unrestricted Hartree-Fock (UHF) computational simulation, Compact effective potentials (CEP), the infrared spectrum of the protonated rhodochrosite crystal, CH19Mn6O8, and the load distribution by the unit molecule by two widely used methods, Atomic Polar Tensor (APT) and Mulliken, were studied. The rhodochrosite crystal unit cell of structure CMn6O8, where the load distribution by the molecule was verified in the UHF CEP-4G (Effective core potential (ECP) minimal basis), UHF CEP-31G (ECP split valance) and UHF CEP121G (ECP triple-split basis). The largest load variation in the APT and Mulliken methods were obtained in the CEP-121G basis set, with δ = 2.922 e δ = 2.650 u. a., respectively, being δAPT > δMulliken. The maximum absorbance peaks in the CEP-4G, CEP-31G and CEP121G basis set are present at the frequencies 2172.23 cm-1 , with a normalized intensity of 0.65; 2231.4 cm-1 and 0.454; and 2177.24 cm-1 and 1.0, respectively. An in-depth study is necessary to verify the absorption by the tumoral and non-tumoral tissues of rhodochrosite, before and after irradiating of synchrotron radiation using Small–Angle X–Ray Scattering (SAXS), Ultra–Small Angle X–Ray Scattering (USAXS), Fluctuation X–Ray Scattering (FXS), Wide–Angle X–Ray Scattering (WAXS), Grazing–Incidence Small–Angle X–Ray Scattering (GISAXS), Grazing–Incidence Wide–Angle X–Ray Scattering (GIWAXS), Small–Angle Neutron Scattering (SANS),Grazing–Incidence Small–Angle Neutron Scattering (GISANS), X–Ray Diffraction (XRD), Powder X–Ray Diffraction (PXRD), Wide–Angle X–Ray Diffraction (WAXD), Grazing– Incidence X–Ray Diffraction (GIXD) and Energy–Dispersive X–Ray Diffraction (EDXRD). Later studies could check the advantages and disadvantages of rhodochrosite in the treatment of cancer through synchrotron radiation, such as one oscillator crystal. Studying the sites of rhodocrosite action may lead to a better understanding of its absorption by healthy and/or tumor tissues, thus leading to a better application of synchrotron radiation to the tumors to eliminate them

Structure Development in Polymers during Fused Filament Fabrication (FFF): An in Situ Small- and Wide-Angle X-ray Scattering Study Using Synchrotron Radiation

Abstract: Microstructure formation in individual layers during fused filament fabrication (FFF) of a Π-shaped multilayer single-walled polymer sample was studied by simultaneous measurement of small- and wide-angle X-ray scattering (SAXS and WAXS, respectively) methods employing synchrotron radiation. We investigated individual layers and the welding zone between individual layers. As a model material, we used isotactic polypropylene (iPP), which is a commodity semicrystalline polymer and has a strong potential as a feedstock material for additive manufacturing. The layers were deposited by an FFF three-dimensional (3D) printer that was custom-built to fit into the synchrotron beamline. WAXS data were utilized to determine the temperature of the irradiated volume. The polymer microstructure was characterized in terms of crystallinity and long-spacing. Avrami analysis indicates that the crystallization behavior of iPP in thin layers is rather similar to that observed in quiescent crystallization of bulk iPP, suggest...

A laboratory-based double X-ray spectrometer for simultaneous X-ray emission and X-ray absorption studies

Abstract: X-ray spectroscopy studies are usually performed using synchrotron radiation sources, which offer bright, coherent, energy-tuneable and monochromatic light. However, the application of synchrotron- ...

Bacteriorhodopsin: Structural Insights Revealed Using X-Ray Lasers and Synchrotron Radiation.

Abstract: Directional transport of protons across an energy transducing membrane—proton pumping—is ubiquitous in biology. Bacteriorhodopsin (bR) is a light-driven proton pump that is activated by a buried al...

Perspectives On Sub–nanometer Level of Electronic Structure of the Synchrotron With Mendelevium Nanoparticles For Elimination of Human Cancer Cells, Tissues and Tumors Treatment Using Mathematica 12.0

Abstract: Mendelevium nanoparticles absorb energy of descendent light and generate some heat in the particle. The generated heat transferred to the surrounding environment and leads to increase in temperature of adjacent points to nanoparticles. Heat variations can be obtained by heat transfer equation. In the current study, thermoplasmonic characteristics of Mendelevium nanoparticles with spherical, core–shell and rod shapes are investigated. In order to investigate these characteristics, interaction of synchrotron radiation emission as a function of the beam energy and Mendelevium nanoparticles were simulated using 3D finite element method. Firstly, absorption and extinction cross sections were calculated. Then, increases in temperature due to synchrotron radiation emission as a function of the beam energy absorption were calculated in Mendelevium nanoparticles by solving heat equation. The obtained results show that Mendelevium nanorods are more appropriate option for using in optothermal human cancer cells, tissues and tumors treatment method. When Mendelevium nanoparticles are subjected to descendent light, a part of light scattered (emission process) and the other part absorbed (non–emission process). The amount of energy dissipation in non–emission process mainly depends on material and volume of nanoparticles and it can be identified by absorption cross section. At the other hand, emission process which its characteristics are depend on volume, shape and surface characteristics of nanoparticles explains by scattering cross section. Sum of absorption and scattering processes which lead to light dissipation is called extinction cross section. DOI: 10.14302/issn.2642-3146.jec-19-3072 Corresponding author: Alireza Heidari, Faculty of Chemistry, California South University, 14731 Comet St. Irvine, CA 92604, USA, Email: Scholar.Researcher.Scientist@gmail.com, Alireza.Heidari@calsu.us

Coherent control in the extreme ultraviolet and attosecond regime by synchrotron radiation.

Abstract: Quantum manipulation of populations and pathways in matter by light pulses, so-called coherent control, is currently one of the hottest research areas in optical physics and photochemistry. The forefront of coherent control research is moving rapidly into the regime of extreme ultraviolet wavelength and attosecond temporal resolution. This advance has been enabled by the development of high harmonic generation light sources driven by intense femtosecond laser pulses and by the advent of seeded free electron laser sources. Synchrotron radiation, which is usually illustrated as being of poor temporal coherence, hitherto has not been considered as a tool for coherent control. Here we show an approach based on synchrotron radiation to study coherent control in the extreme ultraviolet and attosecond regime. We demonstrate this capability by achieving wave-packet interferometry on Rydberg wave packets generated in helium atoms.

Light Curves of a Shock-breakout Material and a Relativistic Off-axis Jet from a Binary Neutron Star System

Abstract: Binary neutron star mergers are believed to eject significant masses with a diverse range of velocities. Once these ejected materials begin to be decelerated by a homogeneous medium, relativistic electrons are mainly cooled down by synchrotron radiation, generating a multiwavelength long-lived afterglow. Analytic and numerical methods illustrate that the outermost matter, the merger shock-breakout material, can be parametrized by power-law velocity distributions $\propto \left(\beta_{\rm c}\Gamma \right)^{-\alpha_s}$. Considering that the shock-breakout material is moving on-axis towards the observer and the relativistic jet off-axis, we compute the light curves during the relativistic and the lateral expansion phase. As a particular case, we successfully describe the X-ray, optical and radio light curves alongside the spectral energy distribution from the recently discovered gravitational-wave transient GW170817, when the merger shock-breakout material moves with mildly relativistic velocities near-Newtonian phase and the jet with relativistic velocities. Future electromagnetic counterpart observations of this binary system could be able to evaluate different properties of these light curves.

Grazing-Incidence Small-Angle X-Ray Scattering (GISAXS) and Grazing-Incidence Wide-Angle X-Ray Scattering (GIWAXS) Comparative Study on Malignant and Benign Human Cancer Cells and Tissues under Synchrotron Radiation

Abstract: In the current study, we have experimentally and comparatively investigated and compared malignant human cancer cells and tissues before and after irradiating of synchrotron radiation using Grazing-Incidence Small-Angle X-Ray Scattering (GISAXS) and Grazing-Incidence Wide-Angle X-Ray Scattering (GIWAXS). It is clear that malignant human cancer cells and tissues have gradually transformed to benign human cancer cells and tissues under synchrotron radiation with the passing of time.

Proton-synchrotron as the radiation mechanism of the prompt emission of GRBs?

Abstract: We discuss the new surprising observational results that indicate quite convincingly that the prompt emission of Gamma-Ray Bursts (GRBs) is due to synchrotron radiation produced by a particle distribution that has a low energy cut-off. The evidence of this is provided by the low energy part of the spectrum of the prompt emission, that shows the characteristic F(nu) \propto nu^(1/3) shape followed by F(nu) \propto nu^(-1/2) up to the peak frequency. This implies that although the emitting particles are in fast cooling, they do not cool completely. This poses a severe challenge to the basic ideas about how and where the emission is produced, because the incomplete cooling requires a small value of the magnetic field, to limit synchrotron cooling, and a large emitting region, to limit the self-Compton cooling, even considering Klein-Nishina scattering effects. Some new and fundamental ingredient is required for understanding the GRBs prompt emission. We propose proton-synchrotron as a promising mechanism to solve the incomplete cooling puzzle.

Megahertz x-ray microscopy at x-ray free-electron laser and synchrotron sources

Abstract: Modern emerging technologies, such as additive manufacturing, bioprinting, and new material production, require novel metrology tools to probe fundamental high-speed dynamics happening in such systems. Here we demonstrate the application of the megahertz (MHz) European X-ray Free-Electron Laser (EuXFEL) to image the fast stochastic processes induced by a laser on water-filled capillaries with micrometer-scale spatial resolution. The EuXFEL provides superior contrast and spatial resolution compared to equivalent state-of-the-art synchrotron experiments. This work opens up new possibilities for the characterization of MHz stochastic processes on the nanosecond to microsecond time scales with object velocities up to a few kilometers per second using XFEL sources.

Constraining the Magnetic Field in the TeV Halo of Geminga with X-Ray Observations

Abstract: Recently, the High Altitude Water Cherenkov (HAWC) collaboration reported the discovery of a TeV halo around the Geminga pulsar. The TeV emission is believed to originate from the inverse Compton scattering of pulsar-injected electrons/positrons off cosmic microwave background photons. During this time, these electrons should inevitably radiate X-ray photons via synchrotron radiation, providing a useful constraint on the magnetic field in the TeV halo. In this work, we analyze the data of XMM-Newton and Chandra, and obtain an upper limit for the diffuse X-ray flux in a 600 '' region around the Geminga pulsar, which is at a level of less than or similar to 10(-14) erg cm(-2)s(-1). By numerically modeling both the X-ray and TeV observations assuming the isotropic diffusion of injected electrons/ positrons, we find that the magnetic field inside the TeV halo is required to be <1 mu G, which is significantly weaker than the typical magnetic field in the interstellar medium. The weak magnetic field together with the small diffusion coefficient inferred from the HAWC observation implies that the Bohm limit of particle diffusion may probably have been achieved in the TeV halo. We also discuss alternative possibilities for the weak X-ray emission, such as the hadronic origin of the TeV emission or a specific magnetic field topology, in which a weak magnetic field and a very small diffusion coefficient might be avoided.

Propagation‐Based X‐Ray Phase‐Contrast Tomography of Mastectomy Samples Using Synchrotron Radiation

Abstract: PURPOSE Propagation-based phase-contrast computed tomography (PB-CT) is a method for three-dimensional x-ray imaging that utilizes refraction, as well as absorption, of x rays in the tissues to increase the signal-to-noise ratio (SNR) in the resultant images, in comparison with equivalent conventional absorption-only x-ray tomography (CT). Importantly, the higher SNR is achieved without sacrificing spatial resolution or increasing the radiation dose delivered to the imaged tissues. The present work has been carried out in the context of the current development of a breast CT imaging facility at the Australian Synchrotron. METHODS Seven unfixed complete mastectomy samples with and without breast cancer lesions have been imaged using absorption-only CT and PB-CT techniques under controlled experimental conditions. The radiation doses delivered to the mastectomy samples during the scans were comparable to those approved for mammographic screening. Physical characteristics of the reconstructed images, such as spatial resolution and SNR, have been measured and compared with the results of the radiological quality assessment of the complete absorption CT and PB-CT image stacks. RESULTS Despite the presence of some image artefacts, the PB-CT images have outperformed comparable absorption CT images collected at the same radiation dose, in terms of both the measured objective image characteristics and the radiological image scores. The outcomes of these experiments are shown to be consistent with predictions of the theory of PB-CT imaging and previous reported experimental studies of this imaging modality. CONCLUSIONS The results presented in this paper demonstrate that PB-CT holds a high potential for improving on the quality and diagnostic value of images obtained using existing medical x-ray technologies, such as mammography and digital breast tomosynthesis (DBT). If implemented at suitable synchrotron imaging facilities, PB-CT can be used to complement existing imaging modalities, leading to more accurate breast cancer diagnosis.

A Fundamental Plane for Gamma-Ray Pulsars

Abstract: We show that the γ-ray pulsar observables, i.e., their total γ-ray luminosity, L(sub γ), spectral cutoff energy, ϵ (sub cut), stellar surface magnetic field, B(sub ⋆), and spin-down power e, obey a relation of the form L(sub γ) = f (ϵ (sub cut), B(sub ⋆), e ), which represents a 3D plane in their 4D logspace. Fitting the data of 88 pulsars of the second Fermi pulsar catalog, we show this relation to be L(sub γ) ∝ ϵ (sub cut)(sup 1.18±0.24 B(sub ⋆)(sup 0.17± 0.05) e(sup 0.41±0.08), a pulsar fundamental plane (FP). We show that the observed FP is remarkably close to the theoretical relation L(sub γ) ∝ ϵ (sub cut)(sup 4/3) B(sub ⋆)(sup 1/6) e(sup 5/12) obtained assuming that the pulsar γ-ray emission is due to curvature radiation by particles accelerated at the pulsar equatorial current sheet just outside the light cylinder. Interestingly, the FP seems incompatible with emission by synchrotron radiation. The corresponding scatter about the FP is ∼0.35 dex and can only partly be explained by the observational errors while the rest is probably due to the variation of the inclination and observer angles. We predict also that ϵ (sub cut) ∝ e (sup 7/16) toward low e for both young and millisecond pulsars implying that the observed death line of γ-ray pulsars is due to ϵ (sub cut) dropping below the Fermi band. Our results provide a comprehensive interpretation of the observations of γ-ray pulsars, setting requirements for successful theoretical modeling.

A compact light source providing high-flux, quasi-monochromatic, tunable X-rays in the laboratory

Abstract: There is a large performance gap between conventional, electron-impact X-ray sources and synchrotron radiation sources. Electron-impact X-ray sources are compact, low to moderate cost, widely available and can have high total flux, but have limited tunability (broad spectrum bremsstrahlung plus fixed characteristic lines) and low brightness. By contrast, synchrotron radiation sources provide extremely high brightness (coherent flux), are tunable and can be monochromatized to a very high degree. However, they are very large and expensive, and typically operated as national user facilities with limited access. An Inverse Compton Scattering (ICS) X-ray source can bridge this gap by providing a narrow-band, high flux and tunable X-ray source that fits into a laboratory at a cost of a few percent of a large synchrotron facility. It works by colliding a high-power laser beam with a relativistic electron beam, in which case the backscattered photons have an energy in the X-ray regime. This paper will describe the working principle of the Lyncean Compact Light Source, a storage-ring based ICS source, its unique beam properties and recent developments that are expected to increase flux and brightness by an order of magnitude compared to earlier versions. Furthermore, it will illustrate how such an X-ray source can be the cornerstone of a local X-ray facility serving applications from diffraction and imaging to scattering and spectroscopy. An overview of demonstrated and potential applications will be provided.

Validation of a Monte Carlo simulation for Microbeam Radiation Therapy on the Imaging and Medical Beamline at the Australian Synchrotron.

Abstract: Microbeam Radiation Therapy (MRT) is an emerging cancer treatment modality characterised by the use of high-intensity synchrotron-generated x-rays, spatially fractionated by a multi-slit collimator (MSC), to ablate target tumours. The implementation of an accurate treatment planning system, coupled with simulation tools that allow for independent verification of calculated dose distributions are required to ensure optimal treatment outcomes via reliable dose delivery. In this article we present data from the first Geant4 Monte Carlo radiation transport model of the Imaging and Medical Beamline at the Australian Synchrotron. We have developed the model for use as an independent verification tool for experiments in one of three MRT delivery rooms and therefore compare simulation results with equivalent experimental data. The normalised x-ray spectra produced by the Geant4 model and a previously validated analytical model, SPEC, showed very good agreement using wiggler magnetic field strengths of 2 and 3 T. However, the validity of absolute photon flux at the plane of the Phase Space File (PSF) for a fixed number of simulated electrons was unable to be established. This work shows a possible limitation of the G4SynchrotronRadiation process to model synchrotron radiation when using a variable magnetic field. To account for this limitation, experimentally derived normalisation factors for each wiggler field strength determined under reference conditions were implemented. Experimentally measured broadbeam and microbeam dose distributions within a Gammex RMI457 Solid Water® phantom were compared to simulated distributions generated by the Geant4 model. Simulated and measured broadbeam dose distributions agreed within 3% for all investigated configurations and measured depths. Agreement between the simulated and measured microbeam dose distributions agreed within 5% for all investigated configurations and measured depths.

Effects of Synchrotron Cooling and Pair Production on Collisionless Relativistic Reconnection

Abstract: High-energy radiation from nonthermal particles accelerated in relativistic magnetic reconnection is thought to be important in many astrophysical systems, ranging from blazar jets and black hole accretion disk coronae to pulsars and magnetar flares. The presence of a substantial density of high-energy photons (>MeV) in these systems can make two-photon pair production (γγ → e − e +) an additional source of plasma particles and can affect the radiative properties of these objects. We present the results of novel particle-in-cell simulations that track both the radiated synchrotron photons and the created pairs, with which we study the evolution of a two-dimensional reconnecting current sheet in pair plasma. Synchrotron radiation from accelerated particles in the current sheet produces hot secondary pairs in the upstream, which are later advected into the current sheet where they are reaccelerated and produce more photons. In the optically thin regime, when most of the radiation is leaving the upstream unaffected, this process is self-regulating and depends only on the background magnetic field and the optical depth of photons to pair production. The extra plasma loading also affects the properties of reconnection. We study how the inflow of the secondary plasma, with multiplicities up to several hundred, reduces the effective magnetization of the plasma, suppressing the acceleration and thus decreasing the high-energy photon spectrum cutoff. This offers an explanation for the weak dependence of the observed gamma-ray cutoff in pulsars on the magnetic field at the light cylinder.

An inverse free electron laser acceleration-driven Compton scattering X-ray source.

Abstract: The generation of X-rays and γ-rays based on synchrotron radiation from free electrons, emitted in magnet arrays such as undulators, forms the basis of much of modern X-ray science. This approach has the drawback of requiring very high energy, up to the multi-GeV-scale, electron beams, to obtain the required photon energy. Due to the limit in accelerating gradients in conventional particle accelerators, reaching high energy typically demands use of instruments exceeding 100's of meters in length. Compact, less costly, monochromatic X-ray sources based on very high field acceleration and very short period undulators, however, may enable diverse, paradigm-changing X-ray applications ranging from novel X-ray therapy techniques to active interrogation of sensitive materials, by making them accessible in energy reach, cost and size. Such compactness and enhanced energy reach may be obtained by an all-optical approach, which employs a laser-driven high gradient accelerator based on inverse free electron laser (IFEL), followed by a collision point for inverse Compton scattering (ICS), a scheme where a laser is used to provide undulator fields. We present an experimental proof-of-principle of this approach, where a TW-class CO2 laser pulse is split in two, with half used to accelerate a high quality electron beam up to 84 MeV through the IFEL interaction, and the other half acts as an electromagnetic undulator to generate up to 13 keV X-rays via ICS. These results demonstrate the feasibility of this scheme, which can be joined with other techniques such as laser recirculation to yield very compact photon sources, with both high peak and average brilliance, and with energies extending from the keV to MeV scale. Further, use of the IFEL acceleration with the ICS interaction produces a train of high intensity X-ray pulses, thus enabling a unique tool synchronized with a laser pulse for ultra-fast strobe, pump-probe experimental scenarios.