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1
Rich, David, Diling Zhu, James Turner, Dehong Zhang, Bruce Hill i Yiping Feng. "The LCLS variable-energy hard X-ray single-shot spectrometer". Journal of Synchrotron Radiation 23, nr 1 (1.01.2016): 3–9. http://dx.doi.org/10.1107/s1600577515022559.
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The engineering design, implementation, operation and performance of the new variable-energy hard X-ray single-shot spectrometer (HXSSS) for the LCLS free-electron laser (FEL) are reported. The HXSSS system is based on a cylindrically bent Si thin crystal for dispersing the incident polychromatic FEL beam. A spatially resolved detector system consisting of a Ce:YAG X-ray scintillator screen, an optical imaging system and a low-noise pixelated optical camera is used to record the spectrograph. The HXSSS provides single-shot spectrum measurements for users whose experiments depend critically on the knowledge of the self-amplified spontaneous emission FEL spectrum. It also helps accelerator physicists for the continuing studies and optimization of self-seeding, various improved mechanisms for lasing mechanisms, and FEL performance improvements. The designed operating energy range of the HXSSS is from 4 to 20 keV, with the spectral range of order larger than 2% and a spectral resolution of 2 × 10−5or better. Those performance goals have all been achieved during the commissioning of the HXSSS.
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Чариков, Ю. Е., i А. Н. Шабалин. "Моделирование коронального источника жесткого рентгеновского излучения в турбулентной плазме солнечных вспышек". Журнал технической физики 91, nr 8 (2021): 1204. http://dx.doi.org/10.21883/jtf.2021.08.51092.20-21.
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The kinetics of electron beams accelerated in the collisional plasma of solar (stellar) flares is considered, taking into account the stationary ion-acoustic mode localized at the magnetic looptop and magnetic fluctuations. The astrophysical aspect of the propagation process is related to the interpretation of hard X-rays in the plasma of flare loops. It is shown that when the plasma density in the coronal part of the solar flare loops does not exceed 1010 cm-3, taking into account the additional scattering on the ion-acoustic mode with the ratio of the turbulence energy density to the thermal energy of the plasma ~5 * 10-5-10-3 and magnetic fluctuations with a level of 5·10-2 does not lead to the appearance of a bright hard X-ray source in the coronal part of the loop in the model with the isotropic pitch-angle distribution of accelerated electrons. In the anisotropic case with a hard electron energy spectrum, the coronal hard X-ray source, in the presence of ion-acoustic turbulence, can exist for a short time after the beginning of turbulence generation. And only in the case of a soft energy spectrum of accelerated electrons (power spectrum index >5) and a relatively high plasma density at the magnetic looptop >1010 cm-3, a bright coronal hard X-ray source is generated at energies of 25-50 keV, regardless of the pitch-angular distribution of accelerated electrons at the moment of injection. A significant effect of turbulence on the distribution of the linear degree of hard X-ray polarization along the loop is shown, leading to a decrease in the extreme values in the coronal part by 5-35%. The integral values of the hard X-ray polarization do not exceed 10%.
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Babayev, Arif, Sukru Cakmaktepe i Deniz Turkoz. "The Energy Spectrum of Carriers between Two Concentric Spheres of Kane-Type Semiconductors". Journal of Nanomaterials 2006 (2006): 1–3. http://dx.doi.org/10.1155/jnm/2006/57519.
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The electronic states of carriers between two concentric spheres of Kane-type semiconductor are theoretically investigated and compared with the results of the parabolic band approximation. Calculations are performed for a hard-wall confinement potential and the eigenstates and the eigenvalues of the Kane Hamiltonian are obtained. Taking into account the real band structure (strong spin-orbital interaction, narrow band gap), the size dependence of the energy of electrons, light holes, and spin-orbital splitting holes in InSb semiconductor concentric spheres are calculated. According to the obtained results both in parabolic and nonparabolic (Kane model) cases, the electron energy levels come close to each other with the increasing of the radius.
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Sahakyan, N. "Investigation of the γ-ray spectrum of CTA 102 during the exceptional flaring state in 2016–2017". Astronomy & Astrophysics 635 (marzec 2020): A25. http://dx.doi.org/10.1051/0004-6361/201936715.
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The flat spectrum radio quasar CTA 102 entered an extended period of activity from 2016 to 2017 during which several strong γ-ray flares were observed. By using Fermi large area telescope data, a detailed investigation of γ-ray spectra of CTA 102 during the flaring period was performed. In several periods, the γ-ray spectrum is not consistent with a simple power-law, having a hard photon index with an index of ∼(1.8−2.0) that shows a spectral cut-off around an observed photon energy of ∼(9−16) GeV. The internal γ-ray absorption via photon-photon pair production on the broad-line-region-reflected photons cannot account for the observed cut-off and break even if the emitting region is very close to the central source. This cut-off and break are likely due to a similar intrinsic break in the energy distribution of emitting particles. The origin of the spectral break is investigated through the multiwavelength modeling of the spectral energy distribution in considering a different location for the emitting region. The observed X-ray and γ-ray data is modeled as inverse Compton scattering of synchrotron and/or external photons on the electron population that produces the radio-to-optical emission, which allowed to constrain the power-law index and cut-off energy in the electron energy distribution. The obtained results are discussed in the context of a diffusive acceleration of electrons in the CTA 102 jet.
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Melrose, D. B. "The Nature of Flat Spectrum Sources". Symposium - International Astronomical Union 175 (1996): 423–26. http://dx.doi.org/10.1017/s0074180900081328.
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Nonthermal radio sources near the Galactic Center with flat or weakly inverted spectra (S((ω) ∝ ωα with α ≳ 0) are attributed to optically thin synchrotron emission from a hard electron energy spectrum, N(ε) ∝ ε–α with a = 1 – 2α ≲ 1, produced by Fermi acceleration or diffusive shock acceleration at multiple shocks combined with a synchrotron pile up. This basic mechanism is also plausible for flat-spectrum AGN.
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Purohit, S., M. K. Gupta, M. B. Chowdhuri, I. Mansuri, M. Bhandarkar, B. K. Shukla, K. Shah i in. "Initial results from time-resolved LaBr based hard x-ray spectrometer for ADITYA-U tokamak". Review of Scientific Instruments 93, nr 9 (1.09.2022): 093512. http://dx.doi.org/10.1063/5.0101310.
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Runaway electrons (REs) are passively studied by hard x-ray (HX) emissions generated by REs. A LaBr3(Ce) detector-based HX spectroscopic diagnostic (operational within ∼75 keV to 3.5 MeV) has been set up on the ADITYA-U. The diagnostic acquisition software utility is upgraded to obtain the temporal evolution of the HX spectrum to understand the RE energy distribution in plasma during its various phases. The peak position moves to lower energy for Ohmically heated discharges (200–80 keV), indicating a relative increase in the thermal particle content in the plasma. The peak position of RE energy shows a decreasing tendency with increasing ne with Ne gas puffing and termination of the electron cyclotron resonance pulse.
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Khangulyan, Dmitry, Andrew M. Taylor i Felix Aharonian. "The Formation of Hard Very High Energy Spectra from Gamma-ray Burst Afterglows via Two-zone Synchrotron Self-Compton Emission". Astrophysical Journal 947, nr 2 (1.04.2023): 87. http://dx.doi.org/10.3847/1538-4357/acc24e.
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Abstract Electron Compton scattering of target photons into the gamma-ray energy band (inverse Compton scattering; IC) is commonly expected to dominate the very high energy (VHE) spectra in gamma-ray bursts (GRBs) especially during the afterglow phase. For sufficiently large center-of-mass energies in these collisions, the effect of the electron recoil starts reducing the scattering cross-section (the Klein–Nishina regime). The IC spectra generated in the Klein–Nishina regime is softer and has a smaller flux level compared to the synchrotron spectra produced by the same electrons. The detection of afterglow emission from nearby GRB190829A in the VHE domain with H.E.S.S. has revealed an unexpected feature: the slope of the VHE spectrum matches well the slope of the X-ray spectra, despite expectations that, for the IC production process, the impact of the Klein–Nishina effect should be strong. The multi-wavelength spectral energy distribution appears to be inconsistent with predictions of one-zone synchrotron–self-Compton models. We study the possible impact of two-zone configuration on the properties of IC emission when the magnetic field strength differs considerably between the two zones. Synchrotron photons from the strong magnetic field zone provide the dominant target for cooling of the electrons in the weak magnetic field zone, which results in a formation of hard electron distribution and consequently of a hard IC emission. We show that the two-zone model can provide a good description of the Swift's X-ray Telescope and VHE H.E.S.S. data.
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Fiocchi, M., F. Onori, A. Bazzano, A. J. Bird, A. Bodaghee, P. A. Charles, V. A. Lepingwell i in. "Evolution of MAXI J1631–479 during the January 2019 outburst observed by INTEGRAL/IBIS". Monthly Notices of the Royal Astronomical Society 492, nr 3 (11.01.2020): 3657–61. http://dx.doi.org/10.1093/mnras/staa068.
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ABSTRACT We report on a recent bright outburst from the new X-ray binary transient MAXI J1631–479, observed in January 2019. In particular, we present the 30–200 keV analysis of spectral transitions observed with INTEGRAL/IBIS during its Galactic plane monitoring program. In the MAXI and BAT monitoring period, we observed two different spectral transitions between the high/soft and low/hard states. The INTEGRAL spectrum from data taken soon before the second transition is best described by a Comptonized thermal component with a temperature of kTe ∼ 30 keV and a high-luminosity value of $L_{2-200\, \mathrm{keV}}\sim 3\times 10^{38}$ erg−1 (assuming a distance of 8 kpc). During the second transition, the source shows a hard, power-law spectrum. The lack of high energy cut-off indicates that the hard X-ray spectrum from MAXI J1631–479 is due to a non-thermal emission. Inverse Compton scattering of soft X-ray photons from a non-thermal or hybrid thermal/non-thermal electron distribution can explain the observed X-ray spectrum although a contribution to the hard X-ray emission from a jet cannot be determined at this stage. The outburst evolution in the hardness-intensity diagram, the spectral characteristics, and the rise and decay times of the outburst are suggesting that this system is a black hole candidate.
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Wadiasingh, Zorawar, Matthew G. Baring, Peter L. Gonthier i Alice K. Harding. "Hard Spectral Tails in Magnetars". Proceedings of the International Astronomical Union 13, S337 (wrzesień 2017): 108–11. http://dx.doi.org/10.1017/s1743921317009073.
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AbstractPulsed non-thermal quiescent emission between 10 keV and around 150 keV has been observed in ~10 magnetars. For inner magnetospheric models of such hard X-ray signals, resonant Compton upscattering of soft thermal photons from the neutron star surface is the most efficient radiative process. We present angle-dependent hard X-ray upscattering model spectra for uncooled monoenergetic relativistic electrons. The spectral cut-off energies are critically dependent on the observer viewing angles and electron Lorentz factor. We find that electrons with energies less than around 15 MeV will emit most of their radiation below 250 keV, consistent with the observed turnovers in magnetar hard X-ray tails. Moreover, electrons of higher energy still emit most of the radiation below around 1 MeV, except for quasi-equatorial emission locales for select pulses phases. Our spectral computations use new state-of-the-art, spin-dependent formalism for the QED Compton scattering cross section in strong magnetic fields.
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Tibaldo, L., R. Zanin, G. Faggioli, J. Ballet, M. H. Grondin, J. A. Hinton i M. Lemoine-Goumard. "Disentangling multiple high-energy emission components in the Vela X pulsar wind nebula with the Fermi Large Area Telescope". Astronomy & Astrophysics 617 (wrzesień 2018): A78. http://dx.doi.org/10.1051/0004-6361/201833356.
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Context. Vela X is a pulsar wind nebula in which two relativistic particle populations with distinct spatial and spectral distributions dominate the emission at different wavelengths. An extended 2° × 3° nebula is seen in radio and GeV gamma rays. An elongated cocoon prevails in X-rays and TeV gamma rays. Aims. We use ~9.5 yr of data from the Fermi Large Area Telescope (LAT) to disentangle gamma-ray emission from the two components in the energy range from 10 GeV to 2 TeV, bridging the gap between previous measurements at GeV and TeV energies. Methods. We determine the morphology of emission associated to Vela X separately at energies <100 and >100 GeV, and compare it to the morphology seen at other wavelengths. Then, we derive the spectral energy distribution of the two gamma-ray components over the full energy range. Results. The best overall fit to the LAT data is provided by the combination of the two components derived at energies <100 and >100 GeV. The first component has a soft spectrum, spectral index 2.19 ± 0.16−0.22+0.05, and extends over a region of radius 1.°36±0.°04, consistent with the size of the radio nebula. The second component has a harder spectrum, spectral index 0.9 ± 0.3−0.1+0.3, and is concentrated over an area of radius 0.°63±0.°03, coincident with the X-ray cocoon that had already been established as accounting for the bulk of the emission at TeV energies. Conclusions. The spectrum measured for the low-energy component corroborates previous evidence for a roll-over of the electron spectrum in the extended radio nebula at energies of a few tens of GeV possibly due to diffusive escape. The high-energy component has a very hard spectrum: if the emission is produced by electrons with a power-law spectrum, the electrons must be uncooled, and there is a hint that their spectrum may be harder than predictions by standard models of Fermi acceleration at relativistic shocks.
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Petrillo, Vittoria, Illya Drebot, Geoffrey Krafft, Cesare Maroli, Andrea R. Rossi, Marcello Rossetti Rossetti Conti, Marcel Ruijter i Balša Terzić. "A Laser Frequency Transverse Modulation Might Compensate for the Spectral Broadening Due to Large Electron Energy Spread in Thomson Sources". Photonics 9, nr 2 (25.01.2022): 62. http://dx.doi.org/10.3390/photonics9020062.
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Compact laser plasma accelerators generate high-energy electron beams with increasing quality. When used in inverse Compton backscattering, however, the relatively large electron energy spread jeopardizes potential applications requiring small bandwidths. We present here a novel interaction scheme that allows us to compensate for the negative effects of the electron energy spread on the spectrum, by introducing a transverse spatial frequency modulation in the laser pulse. Such a laser chirp, together with a properly dispersed electron beam, can substantially reduce the broadening of the Compton bandwidth due to the electron energy spread. We show theoretical analysis and numerical simulations for hard X-ray Thomson sources based on laser plasma accelerators.
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Wang, Dengwang, Ruomeng Ying, Wei Chen i Sheng Wang. "Study on Effects of Energy Deposition and Thermal Shock Wave by Electron Beam Irradiation". Applied Sciences 12, nr 7 (27.03.2022): 3395. http://dx.doi.org/10.3390/app12073395.
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The electron beam is an important way to effectively simulate the thermodynamic effects of an intense pulsed X-ray and the materials for electron beam irradiation are of great significance to study the effects of energy deposition and thermal shock waves. Based on the input conditions like the actual current, voltage, and energy spectrum of an electron beam device (REB), the analytic method and the Monte Carlo method were used to calculate the energy deposition of a multi-energy-spectrum electron beam in materials of hard aluminum and carbon phenolic, the differences of the two methods were analyzed, the energy deposition profiles of different incident angles and energies were obtained, and the energy deposition of electron beam irradiation of a multilayer target was calculated as well. Through the numerical simulation and experimental study of thermal shock waves of electron beam irradiation materials, the calculation error was less than 10% by comparing the stress changes of thermal shock waves with different energies. This is helpful for studying the protective structure of spacecraft.
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Hu, Wen, Da-Hai Yan i Qiang-Lin Hu. "Two-injection Scenario for the Hard X-Ray Excess Observed in Mrk 421". Astrophysical Journal 948, nr 2 (1.05.2023): 82. http://dx.doi.org/10.3847/1538-4357/accc2e.
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Abstract An interesting result that was recently reported for Mrk 421 is the detection of a significant excess at hard X-ray energies, which could provide useful information to investigate particle acceleration and emission mechanisms in the relativistic jet. Considering a two-injection scenario, we develop a self-consistent one-zone leptonic model to understand the origin of the hard X-ray excess in Mrk 421 during the period of extremely low X-ray and very high-energy flux in 2013 January. In the model, two populations of mono-energetic ultra-relativistic electrons are injected into the emission region, which is a magnetized plasmoid propagating along the blazar jet. We numerically calculate the emitting electron energy distribution by solving a kinetic equation that incorporates both shock acceleration and stochastic acceleration processes. Moreover, we infer analytic expressions relating the electrons’ acceleration, cooling, escape, and injection to the observed spectra and variability. In particular, for the injection luminosity, we derive a new approximate analytical expression for the case of continual injection with a mono-energetic distribution. Based on a comparison between the theoretical predictions and the observed SED, we conclude that the hard X-ray excess that was observed in Mrk 421 may be due to the synchrotron radiation emitted by an additional electron population, which is co-spatial with an electron population producing simultaneous optical/UV, soft X-ray, and γ-ray emissions. Therefore, stochastic acceleration may play a major role in producing the observed X-ray spectrum.
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Deng, B., Z. Liu, H. Yang, Q. Zhang, H. Deng i B. Liu. "Proposal of a non-invasive spectrum diagnostic instrumentation for hard X-rays with high repetitions". Journal of Instrumentation 17, nr 05 (1.05.2022): P05046. http://dx.doi.org/10.1088/1748-0221/17/05/p05046.
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Abstract The X-ray free-electron laser (XFEL) is one of the most powerful tools in scientific frontiers due to its ultra-fast pulse duration and high peak brightness. The non-invasive, energy spectrum monitoring of XFEL pulses is an emerging demand to enhance its operation. This work proposes a non-invasive photo-electron spectrometer equipped with four time-of-flight assemblies to monitor the spectrum of high-repetition-rate XFEL. A comprehensive numerical model is established for start-to-end simulations of the instrumentation, through which the performance of the instrumentation is evaluated and optimized. The simulation results suggest that an energy resolution of 0.05 eV can be fully feasible for XFEL pulses around 1 keV. The position and angular response of the TOF assembly are also discussed, which indicates the transverse radius of XFEL pulses is smaller than 1 mm and that the collecting angle of the design is suitable for monitoring.
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Ran, Xianwen, Bo Wang, Kun Zhang i Wenhui Tang. "A Method to Optimize the Electron Spectrum for Simulating Thermo-Mechanical Response to X-ray Radiation". Symmetry 12, nr 1 (27.12.2019): 59. http://dx.doi.org/10.3390/sym12010059.
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The X-ray pulse originating from high altitude nuclear detonation (HAND) is mainly soft X-ray and its intensity is high enough to gasify the penetrated material and then lead to the severe thermo-mechanical deformation of unpenetrated material from the gasified blow-off effect. This effect cannot be directly reproduced in a lab for the lack of the X-ray source like HAND. At present, the low-energy relativistic electron beams resulting from an electron accelerator are usually used to approximately reproduce this effect, but the difference in the energy-deposited profile in materials between the electron and X-ray cannot be eliminated. In this paper, the symmetric linear least squares method was used to optimize the electron spectrum, and the general Monte Carlo N-Particle Transport Code calculations showed the optimized spectrum can produce the same energy-deposited profile in aluminum, copper, and tantalum with the soft X-rays like 1 keV or 3 keV spectrums. This indicates that it is possible to simulate the severe thermo-mechanical deformation resulting from HAND using the optimized electron spectrums.
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Muto, S., S. Morita, S. Kubo, T. Shimozuma, H. Idei i Y. Yoshimura. "First measurement of hard x-ray spectrum emitted from high-energy electrons in electron cyclotron heated plasma of LHD". Review of Scientific Instruments 74, nr 3 (marzec 2003): 1993–96. http://dx.doi.org/10.1063/1.1538329.
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Godleski, John J., Rebecca C. Stearns i Emil J. Millet. "Electron spectroscopic imaging and analysis of electron energy loss spectra with an energy filtering Electron Microscope". Proceedings, annual meeting, Electron Microscopy Society of America 47 (6.08.1989): 404–5. http://dx.doi.org/10.1017/s0424820100153993.
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The Zeiss CEM902, energy filtering electron microscope, can be used to image the structure of unstained 30 nm sections of biologic materials, to image the distribution of selected elements in such sections, and to determine electron energy loss spectra (EELS) of elements in areas as small as 10 nm. Although the integrated computer in the latest version of the CEM902 can collect and display signals from the scintillation detector for recording EELS, our instrument did not have this capability. Therefore, we have added a Leading Edge Model D personal computer with a 20 Mbyte hard disk, Hercules compatible graphics display adapter, and a programmable gain analog to digital converter board (Metrabyte DAS16-G1) to collect and analyze voltage signals corresponding to changes in accelerating voltage and changes in the signal from the photomultiplier tube (PMT) of the scintillation detector. With this board, the gain on the PMT channel is dynamically adjusted for optimal resolution. Software is designed to monitor and display voltages, store data on the hard disk, display spectra with adjustable axes, as well as subtract spectra and determine areas beneath regions of interest.Canine alveolar macrophages with ingested cobalt oxide particles were fixed with 2.5% glutaraldehyde in 0.164M phosphate buffer, post-fixed in 1% OsO4 in 0.lM Na cacodylate buffer, dehydrated through alcohols, embedded in araldite, and sectioned at 30nm. Sections were assessed with our CEM902 as described above. The spectral range of 500 to 900 electron volts while focused on acobalt oxide particle at 20,000x is illustrated in Figure 1 .
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TAO, Y. Z., N. Y. WANG, Y. S. SHAN, Y. J. LI, X. Z. TANG i H. F. ZHANG. "The hard X-ray continuum from intense ultrashort KrF laser–solid interaction". Laser and Particle Beams 20, nr 1 (styczeń 2002): 129–32. http://dx.doi.org/10.1017/s0263034602201196.
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The hard X-ray (>30 keV) continuum from the interaction of a Ti:sapphire/KrF intense femtosecond UV laser (50 mJ, 440 fs, 10 Hz at 248 nm) with a solid has been measured; the intensity on the target is up to 1017 W/cm2. The X-ray with energy of 200 keV has been observed; the temperature of the hot electron from fitting the spectrum utilizing Maxwellian distribution is 67 keV. This is the first measurement of hard X-rays from femtosecond KrF laser–solid interaction.
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Morgner, Harald, i Hubert Seiberle. "Transition state spectroscopy with electrons as studied by 3D-trajectory calculations of the reaction He+ + Br2− → He+Br− + Br". Canadian Journal of Chemistry 72, nr 3 (1.03.1994): 995–1003. http://dx.doi.org/10.1139/v94-128.
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We investigate electron emission from the interaction of metastable helium (ls2s; 23S) with Br2 molecules. A small part of the electron energy spectrum is due to direct Penning ionization, giving rise to spectral features familiar from photoionization of Br2. However, the dominant contribution to electron emission originates from a collision complex that can be described as ion pair state He+–Br2−. In analogy to a collision between the alkali atom Li(2s) and Br2, which leads via Li+–Br2− to salt formation LiBr + Br, this system can be viewed as undergoing a chemical reaction to He+Br− Br. Of course, no stable products He+Br− can be produced in this way since the large recombination energy of He+ causes autoionization to He + Br+ + e−. On the other hand, this situation is ideal if one wishes to study spectroscopically the transition state of a chemical reaction, in our case the development of the system from He(1s2s) + Br2 to (He+Br−) + Br. Neither of the separate reaction partners is able to emit electrons. During the encounter the lifetime against autoionization is so short that decay into the ionized channel cannot occur long after the chemical reaction is complete. Thus, electron emission is confined to the lifetime of the reaction complex. Accordingly, the electron energy spectrum contains information exclusively on the transition state with no blending by emission from educts or products as could be the case in optical spectroscopy. As a case study we carry out 3D-trajectory calculations on the collision complex He+–Br2−, monitoring the energy distribution of emitted electrons throughout the lifetime of the complex. We find that the electron energy spectrum varies strongly from the initial to the final stages of the ongoing chemical reaction.
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Samoylova, Liubov, Ulrike Boesenberg, Aleksandr Chumakov, Vladimir Kaganer, Ilia Petrov, Thomas Roth, Rudolf Rüffer, Harald Sinn, Sergey Terentyev i Anders Madsen. "Diffraction properties of a strongly bent diamond crystal used as a dispersive spectrometer for XFEL pulses". Journal of Synchrotron Radiation 26, nr 4 (6.06.2019): 1069–72. http://dx.doi.org/10.1107/s1600577519004880.
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Self-amplified spontaneous emission (SASE) enables X-ray free-electron lasers (XFELs) to generate hard X-ray pulses of sub-100 fs duration. However, due to the stochastic nature of SASE, the energy spectrum fluctuates from pulse to pulse. Many experiments that employ XFEL radiation require the resolution of the spectrum of each pulse. The work presented here investigates the capacity of a thin strongly bent diamond crystal to resolve the energy spectra of hard X-ray SASE pulses by studying its diffraction properties. Rocking curves of the symmetric C*(440) reflection have been measured for different bending radii. The experimental data match the theoretical modelling based on the Takagi–Taupin equations of dynamical diffraction. A uniform strain gradient has proven to be a valid model of strain deformations in the crystal.
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Rodi, James, E. Jourdain i J. P. Roques. "MAXI J1535–571 2017 Outburst Seen by INTEGRAL/SPI and Investigating the Origin of Its Hard Tail". Astrophysical Journal 935, nr 1 (1.08.2022): 25. http://dx.doi.org/10.3847/1538-4357/ac7fff.
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Abstract On 2017 September 2 MAXI J1535–571 went into outburst and peaked at ∼5 Crab in the 2–20 keV energy range. Early in the flare, the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) performed target of opportunity pointings and monitored the source as it transitioned from the hard state to the soft state. Using quasi-simultaneous observations from MAXI/GSC and INTEGRAL/SPI, we studied the temporal and spectral evolution of MAXI J1535–571 in the 2–500 keV range. Early spectra show a Comptonized spectrum and a high-energy component dominant above ∼150 keV. CompTT fits to the SPectrometer on INTEGRAL (SPI) data found electron temperatures (kT e ) evolve from ∼31 keV to 18 keV with a tied optical depth (τ ∼ 0.85) or τ evolving from ∼1.2–0.65 with a tied kT e (∼24 keV). To investigate the nature of the high-energy component, we performed a spectral decomposition of the 100–400 keV energy band. The CompTT flux varies significantly during the hard state while the high-energy component flux is consistent with a constant flux. This result suggests that the two components originate from different locations, which favors a jet origin interpretation for the high-energy component over a hybrid corona interpretation. Lastly, two short rebrightenings during the hard-to-soft transition are compared to similar events reported in MAXI J1820+070.
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Bellucci, Stefano, Sergei Kruchinin, Stanislav P. Repetsky, Iryna G. Vyshyvana i Ruslan Melnyk. "Behavior of the Energy Spectrum and Electric Conduction of Doped Graphene". Materials 13, nr 7 (6.04.2020): 1718. http://dx.doi.org/10.3390/ma13071718.
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We consider the effect of atomic impurities on the energy spectrum and electrical conductance of graphene. As is known, the ordering of atomic impurities at the nodes of a crystal lattice modifies the graphene spectrum of energy, yielding a gap in it. Assuming a Fermi level within the gap domain, the electrical conductance diverges at the ordering of graphene. Hence, we can conclude about the presence of a metal–dielectric transition. On the other hand, for a Fermi level occurring outside of the gap, we see an increase in the electrical conductance as a function of the order parameter. The analytic formulas obtained in the Lifshitz one-electron strong-coupling model, describing the one-electron states of graphene doped with substitutional impurity atoms in the limiting case of weak scattering, are compared to the results of numerical calculations. To determine the dependence of the energy spectrum and electrical conductance on the order parameter, we consider both the limiting case of weak scattering and the case of finite scattering potential. The contributions of the scattering of electrons on a vapor of atoms to the density of states and the electrical conductance of graphene with an admixture of interstitial atoms are studied within numerical methods. It is shown that an increase in the electrical conductance with the order parameter is a result of both the growth of the density of states at the Fermi level and the time of relaxation of electron states. We have demonstrated the presence of a domain of localized extrinsic states on the edges of the energy gap arising at the ordering of atoms of the admixture. If the Fermi level falls in the indicated spectral regions, the electrical conductance of graphene is significantly affected by the scattering of electrons on clusters of two or more atoms, and the approximation of coherent potential fails in this case.
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Zhang, S. N. "High Energy Continuum Spectra from X-Ray Binaries". International Astronomical Union Colloquium 163 (1997): 41–52. http://dx.doi.org/10.1017/s0252921100042482.
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AbstractA variety of high energy (>1 keV) spectra have been observed in recent years from Black Hole (BH) and Neutron Star (NS) X-ray Binaries (XB). Some common physical components exist between BHXBs and NSXBs, resulting in some high energy spectral features. A common component between a BHXB and a weakly magnetized NSXB is the inner accretion disk region extending very close to the surface (for a NS) or the horizon (for a BH). The inner disk radiation can be described by a multi-color blackbody (MCB) spectral model. The surface radiation of the NS can be approximated by a Single Color Blackbody (SCB) spectrum. For a strongly magnetized NSXB, the high energy emission is from its magnetosphere, characterised by a thermal bremsstrahlung (TB) spectrum. In both BHXBs and weakly magnetized NSXBs, a hot electron cloud may exist, producing the hard X-ray power law (photon index −1.5 to −2.0) with thermal cutoff (50–200 keV). It has been recently proposed that a converging flow may be formed near the horizon of a BH, producing a softer power law (photon index about −2.5) without cutoff up to several hundred keV. Based on these concepts we also discuss possible ways to distinguish between BH and NS XBs. Finally we discuss briefly spectral state transitions in both BH and NS XBs.
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Bassi, T., J. Malzac, M. Del Santo, E. Jourdain, J.-P. Roques, A. D’Aì, J. C. A. Miller-Jones i in. "On the nature of the soft γ-ray emission in the hard state of the black hole transient GRS 1716−249". Monthly Notices of the Royal Astronomical Society 494, nr 1 (18.03.2020): 571–83. http://dx.doi.org/10.1093/mnras/staa739.
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ABSTRACT The black hole transient GRS 1716−249 was monitored from the radio to the γ-ray band during its 2016–2017 outburst. This paper focuses on the spectral energy distribution (SED) obtained in 2017 February–March, when GRS 1716−249 was in a bright hard spectral state. The soft γ-ray data collected with the INTEGRAL/SPI telescope show the presence of a spectral component that is in excess of the thermal Comptonization emission. This component is usually interpreted as inverse Compton emission from a tiny fraction of non-thermal electrons in the X-ray corona. We find that hybrid thermal/non-thermal Comptonization models provide a good fit to the X-/γ-ray spectrum of GRS 1716−249. The best-fitting parameters are typical of the bright hard state spectra observed in other black hole X-ray binaries. Moreover, the magnetized hybrid Comptonization model belm provides an upper limit on the intensity of the coronal magnetic field of about 106 G. Alternatively, this soft γ-ray emission could originate from synchrotron emission in the radio jet. In order to test this hypothesis, we fit the SED with the irradiated disc plus Comptonization model combined with the jet internal shock emission model ishem. We found that a jet with an electron distribution of p ≃ 2.1 can reproduce the soft γ-ray emission of GRS 1716−249. However, if we introduce the expected cooling break around 10 keV, the jet model can no longer explain the observed soft γ-ray emission, unless the index of the electron energy distribution is significantly harder (p < 2).
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Fletcher, L. B., C. B. Curry, M. Gauthier, G. D. Glenn, Z. Chen, E. Cunningham, A. Descamps i in. "Investigation of hard x-ray emissions from terawatt laser-irradiated foils at the Matter in Extreme Conditions instrument of the Linac Coherent Light Source". Journal of Instrumentation 17, nr 04 (1.04.2022): T04004. http://dx.doi.org/10.1088/1748-0221/17/04/t04004.
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Abstract In this technical report, we investigate the hard x-ray background produced at the Matter in Extreme Conditions (MEC) instrument of the Linac Coherent Light Source (LCLS) from the interaction of a high-intensity (∼1019 W/cm2) femtosecond laser with solid μm-thick aluminum and polypropylene targets. This background is dominated by bremsstrahlung from laser-generated relativistic electrons, and a measurement of the broadband x-ray spectrum via differential x-ray energy filtering was used to infer the existence of two electron distributions with electron temperatures of Thot = 500 ± 300 keV and Tcold = 5.0 ± 0.5 keV. Simultaneous single-shot measurements of the proton energies accelerated from laser-irradiated solid targets could be correlated with these measurements to further constrain the on-target laser parameters. Measurements of the hard x-ray photon background generated from laser-irradiated foils can be used to directly monitor and test the signal-to-background limits of silicon-based hybrid pixel array x-ray detectors at laser intensities approaching 1019 W/cm2.
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Ding, G. Q., J. L. Qu, L. M. Song, Y. Huang, S. Zhang, Q. C. Bu, M. Y. Ge i in. "Insight-HXMT Detections of Hard X-Ray Tails in Scorpius X-1". Astrophysical Journal 950, nr 1 (1.06.2023): 69. http://dx.doi.org/10.3847/1538-4357/accf91.
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Abstract Using the observations of the high-energy detector of the Hard X-ray Modulation Telescope (Insight-HXMT) for Scorpius X-1 from 2017 to 2020, we search for hard X-ray tails in the X-ray spectra in ∼30–200 keV. The hard X-ray tails are found throughout the Z-track on the hardness–intensity diagram, and the detected hard X-ray tails become hard and weak from the horizontal branch (HB), through the normal branch (NB), to the flaring branch (FB). Comparing the hard X-ray spectra of Insight-HXMT between Cyg X-1 and Sco X-1, it is concluded that the hard X-ray spectrum of Cyg X-1 shows a high-energy cutoff, implying a hot corona in it, but the high-energy cutoff is not seen in the hard X-ray spectrum of Sco X-1. From fitting the broadband spectrum of Sco X-1 in ∼2–200 keV, it is proposed that the hard X-ray tails in the HB and NB can be explained by the overall Comptonization COMPTB model, suggesting that the hard X-ray tails could have resulted from the Comptonization of the photons from the neutron star (NS) surface by the thermal electrons in the region between the NS and the disk and the energetic electrons in the freefall toward the NS in the converging flow onto the NS. However, this model cannot be responsible for the hard X-ray tails in the FB. Further study on the FB hard X-ray tails is needed.
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Vilmer, N. "Solar Hard X-Ray and Gamma-Ray Observations from GRANAT". International Astronomical Union Colloquium 142 (1994): 611–21. http://dx.doi.org/10.1017/s0252921100077885.
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AbstractHard X-rays and gamma-rays are the most direct signature of the energetic electrons and ions which are accelerated during solar flares. Since the beginning of 1990 the PHEBUS instrument and the SIGMA anticoincidence shield aboard GRANAT have provided hard X-ray and gamma-ray observations of solar bursts in the energy range 0.075-124 and 0.200-15 MeV, respectively. After a brief description of the experiments, we present some results obtained on solar bursts recorded in 1990 and 1991 June. Special emphasis is given to the results related with particle acceleration during solar flares.The first part of the review is devoted to the constraints obtained on the electron acceleration timescale through the analysis of the temporal characteristics of the bursts. Combined studies of hard X-ray and gamma-ray emissions from PHEBUS and radio emissions from the Nançay Multifrequency Radioheliograph are used to infer constraints on the coronal magnetic topology involved in flares. The characteristics (location, spectrum) of the radio-emitting sources are found to vary within a flare from one hard X-ray peak to the other. Hard X-ray and gamma-ray burst onsets and rapid increases of the > 10 MeV emission are coincident with changes in the associated radio emission pattern. These results will be discussed in the context of the flare energy release.The second part of the paper concerns the heliocentric angle distribution of > 10 MeV events and presents more detailed observations of some of the largest flares in the gamma-ray line and the high-energy domains produced by ultrarelativistic electrons and > 100 MeV nucleon−1 ions. The PHEBUS observations of the gamma-ray line flare of 11 June 1991 have been used to deduce the hardness of the accelerated ion spectrum. The link between the main part of the flare and the late long-lasting >50 MeV emission detected by EGRET/COMPTON is discussed. Finally some observations of the large 1990 May 24 flare which produced a large neutron event at ground level are presented.Subject headings: acceleration of particles — Sun: flares — Sun: radio radiation — Sun: X-rays, gamma rays
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Wang, Wen, Andrea Francesco Battaglia, Säm Krucker i Linghua Wang. "The 2013 November 12 Solar Energetic Electron Event Associated with Solar Jets". Astrophysical Journal 950, nr 2 (1.06.2023): 118. http://dx.doi.org/10.3847/1538-4357/accc86.
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Abstract We investigate the hard X-ray (HXR) flare-associated “prompt” solar energetic electron (SEE) 2013 November 12 event with joint EUV jet observations from Solar Dynamics Observatory/Atmospheric Imaging Assembly and STEREO-A/EUVI. The SEE energy spectrum observed by Wind/3D Plasma and Energetic Particle shows a triple-power-law shape with a low-energy break of 10.0 ± 1.7 keV and a high-energy break of 56.6 ± 8.9 keV, which has never been reported before for jet-related SEE events. Associated HXR emissions observed by RHESSI and FGST/Gamma-ray Burst Monitor show three distinctive peaks with different spectral indices β HPE of HXR-producing electrons (HPEs) derived by means of thick-target bremsstrahlung model. The high-energy spectral index β 3 = 4.63 ± 0.65 of SEE is consistent with the HPE spectral index β HPE derived in HXR peak 1 but different from β HPE of HXR peak 2 and peak 3. The main stream of EUV jets reaches a speed of 370 ± 25 km s−1 after an acceleration of up to 2.9 ± 0.4 km s−2 in a timescale of ∼2 minutes, and the acceleration time coincides with the decay phase of HXR peak 1. EUV observations from two different viewing directions help to reconstruct the jet magnetic configurations. After the investigation on HXR emissions and jet configurations, the interchange-reconnection model triggered by the emerging flux could be a satisfactory explanation for this jet event.
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Cristofari, Pierre. "The transition from Galactic to extragalactic cosmic rays: The high–energy end of the Galactic spectrum". EPJ Web of Conferences 283 (2023): 04002. http://dx.doi.org/10.1051/epjconf/202328304002.
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Understanding the transition from Galactic to extragalactic cosmic rays (CRs) is essential to make sense of the Local cosmic ray spectrum. Several models have been proposed to account for this transition in the 0.1 - 10 × 1018 eV range. For instance: ankle models, where the change from a steep Galactic component to a hard extragalactic spectrum occurs in the 4 − 10 × 1018 eV region, dip models, where the interactions of CR protons with the CMB producing electron-positron pairs shape the ankle, or mixed composition models, in which extragalactic CRs are composed of nuclei of various types. In all these scenarios, the low-energy part of the transition involves the high-energy part of the Galactic component. Therefore, any information on the Galactic component, such as maximum energy, chemical composition, and spectrum after propagation, is crucial to understanding the Galactic-extragalactic transition. We briefly review the high-energy part of the CR spectrum expected from the best potential sources of Galactic CRs.
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Beck, Geoff. "Hunting dark matter in galaxy clusters with non-thermal electrons". Monthly Notices of the Royal Astronomical Society 494, nr 1 (24.03.2020): 1128–32. http://dx.doi.org/10.1093/mnras/staa806.
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ABSTRACT The electron population inferred to be responsible for the mini-halo within the Ophiuchus galaxy cluster is a steep power law in energy with a slope of 3.8. This is substantially different to that predicted by dark matter (DM) annihilation models. In this work, we present a method of indirect comparison between the observed electron spectrum and that predicted for indirect DM emissions. This method utilizes differences in the consequences of a given electron distribution on the subsequent spectral features of synchrotron emissions. To fully exploit this difference, by leveraging the fact that the peak and cut-off synchrotron frequencies are substantially different to hard power-law cases for WIMP masses above ∼50 GeV, we find that we need μJy sensitivities at frequencies above 10 GHz while being sensitive to arcminute scales. We explore the extent to which this electron spectrum comparison can be validated with the up-coming next-generation Very Large Array (ngVLA) instrument. We show that, with the ngVLA, this method allows us to produce far stronger constraints than existing VLA data, indeed these exceed the Fermi-LAT dwarf searches in a wide variety of annihilation channels and for all studied magnetic field scenarios.
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Sahakyan, N. "Broad-band study of high-synchrotron-peaked BL Lac object 1ES 1218+304". Monthly Notices of the Royal Astronomical Society 496, nr 4 (2.07.2020): 5518–27. http://dx.doi.org/10.1093/mnras/staa1893.
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ABSTRACT The origin of the multiwavelength emission from the high-synchrotron-peaked BL Lac 1ES 1218+304 is studied using the data from SwiftUVOT/XRT, NuSTAR, and Fermi-LAT. A detailed temporal and spectral analysis of the data observed during 2008–2020 in the γ-ray (>100 MeV), X-ray (0.3–70 keV), and optical/UV bands is performed. The γ-ray spectrum is hard with a photon index of 1.71 ± 0.02 above 100 MeV. The SwiftUVOT/XRT data show a flux increase in the UV/optical and X-ray bands; the highest 0.3–3 keV X-ray flux was (1.13 ± 0.02) × 10−10 erg cm−2 s−1. In the 0.3–10 keV range, the averaged X-ray photon index is >2.0 which softens to 2.56 ± 0.028 in the 3–50 keV band. However, in some periods, the X-ray photon index became extremely hard (<1.8), indicating that the peak of the synchrotron component was above 1 keV, and so 1ES 1218+304 behaved like an extreme synchrotron BL Lac. The hardest X-ray photon index of 1ES 1218+304 was 1.60 ± 0.05 on MJD 58489. The time-averaged multiwavelength spectral energy distribution is modelled within a one-zone synchrotron self-Compton leptonic model using a broken power law and power law with an exponential cutoff electron energy distributions. The data are well explained when the electron energy distribution is $E_{\rm e}^{-2.1}$ extending up to γbr/cut ≃ (1.7 − 4.3) × 105, and the magnetic field is weak (B ∼ 1.5 × 10−2 G). By solving the kinetic equation for electron evolution in the emitting region, the obtained electron energy distributions are discussed considering particle injection, cooling, and escape.
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Bitter, Olivia Meredith, i Dan Hooper. "Constraining the local pulsar population with the cosmic-ray positron fraction". Journal of Cosmology and Astroparticle Physics 2022, nr 10 (1.10.2022): 081. http://dx.doi.org/10.1088/1475-7516/2022/10/081.
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Abstract Observations of the TeV halos associated with nearby pulsars indicate that these objects inject significant fluxes of very high-energy electron-positrons pairs into the interstellar medium (ISM), thereby likely providing the dominant contribution to the cosmic-ray positron flux. In this paper, we use the cosmic-ray positron fraction as measured by the AMS-02 Collaboration to constrain the characteristics of the local pulsar population. For reasonable model parameters, we find that we can obtain good agreement with the measured positron fraction up to energies of Ee ∼ 300 GeV. At higher energies, the positron fraction is dominated by a small number of pulsars, making it difficult to reliably predict the shape of the expected positron fraction. The low-energy positron spectrum supports the conclusion that pulsars typically transfer approximately η ∼ 5–20% of their total spindown power into the production of very high-energy electron-positron pairs, producing a spectrum of such particles with a hard spectral index, α ∼ 1.5–1.7. Such pulsars typically spindown on a timescale on the order of τ ∼ 104 years. Our best fits were obtained for models in which the radio and gamma-ray beams from pulsars are detectable to 28% and 62% of surrounding observers, respectively.
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Maia, A. V. D. M., i K. Bakke. "On an electron in an elastic medium with a spiral dislocation". International Journal of Modern Physics A 34, nr 27 (27.09.2019): 1950153. http://dx.doi.org/10.1142/s0217751x19501537.
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Topological effects of a spiral dislocation on an electron are investigated when it is confined to a hard-wall confining potential. Besides, the influence of the topology of the spiral dislocation on the interaction of the electron with a nonuniform radial electric field and a uniform axial magnetic field is analyzed. It is shown that the spectrum of energy can be obtained in all these cases. Moreover, it is shown that there is one case where an analog of the Aharonov–Bohm effect for bound states is yielded by the topology of the spiral dislocation.
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Bespalov, P. A., V. V. Zaitsev i A. V. Stepanov. "Energetic Particles in a Flare Loop: Spectra and Radiation Signatures". Symposium - International Astronomical Union 142 (1990): 421–27. http://dx.doi.org/10.1017/s0074180900088343.
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It has been shown that high energy particle spectra, particle dynamics, and radiation in a flare loop are determined by wave-particle interactions. The electron-whistler interaction occurs under conditions of strong pitch angle diffusion that makes the particle distribution function isotropic. The flare loop electrons retain information about the particle source spectrum. The interaction of energetic ions with Alfven waves is characterized by strong, moderate, and weak diffusion. The time delays in hard X-ray and gamma-ray emission during one-step acceleration processes might be understood in terms of a trap-plus-turbulent propagation model. The density of precipitating particles is less than or equal to the trapping one. Radiation signatures of flare loop electrons are discussed.
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Hu, Chun Lian, i Shang Lin Hou. "Study on Microstructure of NiCrMoY Alloy Coatings". Applied Mechanics and Materials 577 (lipiec 2014): 62–65. http://dx.doi.org/10.4028/www.scientific.net/amm.577.62.
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The microstructure of rare earth NiCrMoY alloy manufactured by atomization and oxygen-acetylene flame spray and high frequency induction remelting technique is investigated by a combination of scanning electron microscopy (SEM), energy spectrum, X-ray diffraction meter (XRD). The results indicate that Microstructure of NiCrMoY alloy coatings are finer and bulk-and needle-like hard Metallograph are precipitated, a new phase MoB is produced.
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Panontin, E., A. Dal Molin, M. Nocente, G. Croci, J. Eriksson, L. Giacomelli, G. Gorini i in. "Comparison of unfolding methods for the inference of runaway electron energy distribution from γ-ray spectroscopic measurements". Journal of Instrumentation 16, nr 12 (1.12.2021): C12005. http://dx.doi.org/10.1088/1748-0221/16/12/c12005.
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Abstract Unfolding techniques are employed to reconstruct the 1D energy distribution of runaway electrons from Bremsstrahlung hard X-ray spectrum emitted during plasma disruptions in tokamaks. Here we compare four inversion methods: truncated singular value decomposition, which is a linear algebra technique, maximum likelihood expectation maximization, which is an iterative method, and Tikhonov regularization applied to χ 2 and Poisson statistics, which are two minimization approaches. The reconstruction fidelity and the capability of estimating cumulative statistics, such as the mean and maximum energy, have been assessed on both synthetic and experimental spectra. The effect of measurements limitations, such as the low energy cut and few number of counts, on the final reconstruction has also been studied. We find that the iterative method performs best as it better describes the statistics of the experimental data and is more robust to noise in the recorded spectrum.
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WANG, XIANG-YU, HAO-NING HE i ZHUO LI. "KLEIN–NISHINA EFFECTS IN THE PROMPT AND EXTENDED HIGH-ENERGY GAMMA-RAY EMISSION OF GAMMA-RAY BURSTS". International Journal of Modern Physics D 20, nr 10 (wrzesień 2011): 2023–27. http://dx.doi.org/10.1142/s0218271811020111.
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Prompt and extended high-energy (> 100 MeV) gamma-ray emission has been observed from more than ten gamma-ray bursts by Fermi Large Area Telescope (LAT). Such emission is likely to be produced by synchrotron radiation of electrons accelerated in internal or external shocks. We show that IC scattering of these electrons with synchrotron photons are typically in the Klein–Nishina (KN) regime. For the prompt emission, the KN effect can suppress the IC component and as a result, one single component is seen in some strong bursts. The KN inverse-Compton cooling may also affect the low-energy electron number distribution and hence result in a hard low-energy synchrotron photon spectrum. During the afterglow, KN effect makes the Compton-Y parameter generally less than 1 in the first seconds for a wide range of parameter space. Furthermore, we suggest that the KN effect can explain the somewhat faster-than-expected decay of the early-time high-energy emission observed in GRB090510 and GRB090902B.
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Chollet, Matthieu, Roberto Alonso-Mori, Marco Cammarata, Daniel Damiani, Jim Defever, James T. Delor, Yiping Feng i in. "The X-ray Pump–Probe instrument at the Linac Coherent Light Source". Journal of Synchrotron Radiation 22, nr 3 (21.04.2015): 503–7. http://dx.doi.org/10.1107/s1600577515005135.
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The X-ray Pump–Probe instrument achieves femtosecond time-resolution with hard X-ray methods using a free-electron laser source. It covers a photon energy range of 4–24 keV. A femtosecond optical laser system is available across a broad spectrum of wavelengths for generating transient states of matter. The instrument is designed to emphasize versatility and the scientific goals encompass ultrafast physical, chemical and biological processes involved in the transformation of matter and transfer of energy at the atomic scale.
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Hongbin, Xu, Hu Jianjun, Li Hui, Mao Rongshan, Sun Fei i Hou Tianfeng. "Study of Alloying Process on 40Cr Surface with Electron Beam after Electroplated Cr Layer". Advances in Materials Science and Engineering 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/984231.
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The electroplated hard chromium coat was selected as precoating to improve surface properties of 40Cr. Then electron beam alloying process was experimentalized. The relation rules were summarized between alloying process parameters and overall surface properties by surface morphology observation, surface energy spectrum analysis, EDX analysis in section, and XRD. Experiment results showed that the microcracks appeared on surface of electron beam alloying specimen. Microcracks could disappear when the orthogonal experimental optimum process was used. The matrix metal elements diffused into metal coating surface after electron beam treatment. The maximum depth of alloyed layer could reach 8 μm after electron beam alloying treatment, and electron beam alloying process generated new residual austenite phase.
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Paperny, V. L., I. V. Romanov, A. A. Kologrivov, V. I. Krasov, Yu V. Korobkin i A. A. Rupasov. "Emission of anomalously hard x-ray radiation by a target upon exposition with an electron beam, ejected by a low-energy vacuum discharge with laser ignition". Physics of Plasmas 29, nr 6 (czerwiec 2022): 063102. http://dx.doi.org/10.1063/5.0090368.
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The characteristics of x-ray radiation of a target that is bombarded by a beam of accelerated electrons ejected by a low-power vacuum discharge with laser ignition are studied. It is shown that the maximum radiation energy exceeds the applied potential difference across the discharge gap by almost an order of magnitude and is inversely proportional to the mass of the cathode material ablated by laser radiation. The energy spectrum of x-ray radiation reconstructed from the radiation attenuation curve by filters-absorbers of various thicknesses showed that in the maximum acceleration mode the average energy of the main part of the spectrum is more than four times higher than the voltage across the discharge gap at the moment of beam emission. Possible mechanisms providing anomalous acceleration of electrons in the discharge are considered.
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Çakmak, Seyfettin. "Energy Spectrum of Carriers in a Kane-type Semiconductor Anti-wire". Zeitschrift für Naturforschung A 60, nr 8-9 (1.09.2005): 593–98. http://dx.doi.org/10.1515/zna-2005-8-906.
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The electronic states of a Kane-type semiconductor anti-wire with and without a magnetic field are theoretically investigated. The eigenvalues and eigenstates of Kane’s Hamiltonian are obtained. The calculations are performed for a hard-wall confinement potential, and electronic states are obtained as functions of the magnetic field applied along the cylinder axis. The size dependences of the effective g-value in InSb for electrons and light holes are calculated. The effective g-values of the electrons and light holes decreased with decreasing anti-wire radius.
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Lacki, Brian C., i Todd A. Thompson. "Cosmic rays and high energy emission from starburst galaxies". Proceedings of the International Astronomical Union 7, S284 (wrzesień 2011): 393–96. http://dx.doi.org/10.1017/s1743921312009489.
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AbstractThe nearby starburst galaxies M82 and NGC 253 are now detected in GeV and TeV γ-rays, allowing us to directly study cosmic rays (CRs) in starburst galaxies. Combined with radio observations, the detections constrain the propagation and density of CRs in these starbursts. We discuss the implications for “proton calorimetry”, whether CR protons cool through pion losses before escaping these galaxies. The ratio of γ-ray and radio luminosities constrains how much of the CR electron cooling is due to synchrotron losses. As for leptonic emission, we predict that synchrotron and Inverse Compton emission make up ~1–10% of the unresolved hard X-ray emission from M82, and a few percent or less of the total X-ray emission from starbursts. A detection of these components would inform us of the magnetic field strength and 10 – 100 TeV electron spectrum. We conclude by discussing the prospects for detecting leptonic MeV γ-rays from starbursts and the cosmic γ-ray background.
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Van Oss, R. F., G. H. J. Van Den Oord i M. Kuperus. "Accretion Disk Flares in Energetic Radiation Fields". Symposium - International Astronomical Union 157 (1993): 217–18. http://dx.doi.org/10.1017/s0074180900174157.
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We consider the physics of magnetic flares in the energetic radiation field of an accretion disk corona (ADC). The X-ray emission from these flares is thought to be responsable for the observed hard powerlaw component in the X-ray spectra of galactic black hole candidates in their ‘high’ spectral state. During the flare event (inverse Compton) scattering of soft photons from the underlying disk into hard photons occurs on accelerated electrons in current sheets. The electrons are decelerated by the radiation drag force that results from the up-scattering. This friction-like effect of the intense background radiation field on the motion of the electrons in the sheet can be considered as a form of resistivity in the magnetohydrodynamical picture of the current sheet: Compton resistivity. A spectrum is derived for the up-scattered radiation from current sheets in the ADC and it is found that this spectrum mimics a powerlaw above a critical photon energy.
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Varga, L., i D. Venkatesan. "Detection of very soft X-ray spectra by balloon-borne detectors". Canadian Journal of Physics 69, nr 8-9 (1.08.1991): 999–1006. http://dx.doi.org/10.1139/p91-158.
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A balloon payload launched from Cold Lake, Alta., Canada, on October 14, 1982, measured the spectrum of X rays (E = 20–160 keV) with a hard and a very soft component. The latter contributes significantly only to the 20–40 keV channel; thus a "flapping motion" at the lower energy end of the composite spectrum is observed. We have simulated, using the Monte-Carlo technique, the propagation of X rays through the atmosphere and determined the e-folding energy of the very soft component, which we estimate to be 5 keV, at a particular time (10:45 UT). The electron spectrum producing this soft X-ray source agrees well with in situ satellite and rocket-borne measurements of electron spectra during active auroras. Simulataneous auroral optical emissions (5577 Å (1 Å = 10−10 m)) by a ground-based all-sky charge-coupled device camera are also available for comparison. We also determine the count rate ratio between 20–40 and 60–80 keV channels as a parameter of the variability of the intensity of the very soft component. The time-changes of this ratio and that of the auroral optical emission intensity near the vicinity of the balloon are correlated. The lack of correlation at some other times is ascribed to differences in the behavior of the low- and high-energy ends of the elecron spectrum.
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Cheng, Shikui, Jie Zhang, Yipo Zhang, Li He, Hongbing Xu, Yuxuan Zhu, Xuwen Zhan, Zhongbing Shi i Wulv Zhong. "Development of hard X-ray spectrometer with full digital data acquisition for runaway electron studies at HL-2M". Journal of Instrumentation 18, nr 02 (1.02.2023): T02006. http://dx.doi.org/10.1088/1748-0221/18/02/t02006.
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Abstract The development of hard X-ray (HXR) spectrometers with full digital data acquisition for runaway electron studies on the HL-2M tokamak is presented. Consisting of large-sized NaI:Tl detectors and high-performance multichannel analyzers, this system can realize the measurement of HXR with energies ranging from 0.5 to 10 MeV, and spectrum temporal resolution of 1 ms. An average energy resolution of 56 keV at 662 keV has been achieved at counts rates of about 100 kcps. The spectra data is acquired by a digital-based data acquisition system with fast digitization and software signal processing technology. The energy calibrations are performed by using several radioisotope gamma-ray sources, and the detection efficiencies are simulated by MCNP code. First experimental results from HL-2M Ohmic discharges are presented in this paper.
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Zhang, Qiang, Yong-Feng Huang i Hong-Shi Zong. "MODELING THE MULTI-BAND AFTERGLOW OF GRB 091127: EVIDENCE OF A HARD ELECTRON ENERGY SPECTRUM WITH AN INJECTION BREAK". Astrophysical Journal 811, nr 2 (24.09.2015): 83. http://dx.doi.org/10.1088/0004-637x/811/2/83.
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Bhatta, Gopal, Maksym Mohorian i Illya Bilinsky. "Hard X-ray properties of NuSTAR blazars". Astronomy & Astrophysics 619 (listopad 2018): A93. http://dx.doi.org/10.1051/0004-6361/201833628.
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Context. Investigation of the hard X-ray emission properties of blazars is key to the understanding of the central engine of the sources and associated jet process. In particular, simultaneous spectral and timing analyses of the intraday hard X-ray observations provide us a means to peer into the compact innermost blazar regions that are not accessible to our current instruments. Aims. The primary objective of the work is to associate the observed hard X-ray variability properties in blazars with their flux and spectral states, thereby, based on the correlation among these states, extract the details about the emission regions and processes occurring near the central engine. Methods. We carried out timing, spectral, and cross-correlation analysis of 31 NuSTAR observations of 13 blazars. We investigated the spectral shapes of the sources using single power-law, broken power-law, and log-parabola models. We also studied the co-relation between the soft and hard emission using z-transformed discrete correlation function. In addition, we attempted to constrain the smallest emission regions using minimum variability timescales derived from the light curves. Results. We found that, for most of the sources, the hard X-ray emission can be well represented by the log-parabola model and that the spectral slopes for different blazar subclasses are consistent with the so-called blazar sequence. We also report the steepest spectra (Γ ∼ 3) in the BL Lacertae PKS 2155–304 and the hardest spectra (Γ ∼ 1.4) in the flat-spectrum radio quasar PKS 2149–306. In addition, we noted a close connection between the flux and spectral slope within the source subclass in the sense that high flux and/or flux states tend to be harder in spectra. In BL Lacertae objects, assuming particle acceleration by diffusive shocks and synchrotron cooling as the dominant processes governing the observed flux variability, we constrain the magnetic field of the emission region to be a few Gauss; whereas in flat-spectrum radio quasars, using external Compton models, we estimate the energy of the lower end of the injected electrons to be a few Lorentz factors.
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Osaka, Taito, Ichiro Inoue, Ryota Kinjo, Takashi Hirano, Yuki Morioka, Yasuhisa Sano, Kazuto Yamauchi i Makina Yabashi. "A micro channel-cut crystal X-ray monochromator for a self-seeded hard X-ray free-electron laser". Journal of Synchrotron Radiation 26, nr 5 (27.08.2019): 1496–502. http://dx.doi.org/10.1107/s1600577519008841.
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A channel-cut Si(111) crystal with a channel width of 90 µm was developed for achieving reflection self-seeding in hard X-ray free-electron lasers (XFELs). With the crystal a monochromatic seed pulse is produced from a broadband XFEL pulse generated in the first undulator section with an optical delay of 119 fs at 10 keV. The small optical delay allows a temporal overlap between the seed optical pulse and the electron bunch by using a small magnetic chicane for the electron beam placed between two undulator sections. Peak reflectivity reached 67%, which is reasonable compared with the theoretical value of 81%. By using this monochromator, a monochromatic seed pulse without broadband background in the spectrum was obtained at SACLA with a conversion efficiency from a broadband XFEL pulse of 2 × 10−2, which is ∼10 times higher than the theoretical efficiency of transmission self-seeding using a thin diamond (400) monochromator.
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Kluźniak, W., M. Ruderman, J. Shaham i M. Tavani. "Low Energy Galactic Center Gamma Rays from Low Mass X-Ray Binaries". Symposium - International Astronomical Union 136 (1989): 627–32. http://dx.doi.org/10.1017/s0074180900187121.
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The hard X-ray and low energy γ-ray emission from the galactic center region (GCR) has four components: a power-law continuum between 20/50 keV and 200/300 keV with a power-law photon index β in the range ~ 2.5 to ~ 3.1; a harder spectrum with β ~ 1.–1.5 between 200/300 keV and ~ 511 keV; a narrow electron-positron annihilation line at 511 keV, reported to disappear in less than < 1/2 yr, although the temporal variation is controversial; and an equally variable continuum emission between 511 keV and several MeV (“MeV bump”). All four have luminosities 1037–1038 erg s−1, if they are located 10 kpc away. We propose non-thermal processes in low mass X-ray binaries (LMXB's) concentrated in the galactic bulge as the direct source of the three continuum components of the emission, as well as of an escaping electron-positron e± wind whose positron annihilation relatively far from the star could be the source of the 511 keV line. We consider a model for energetic emission from LMXB's that reproduces the softer power-law component of the GCR continuum through synchrotron emission of relativistic electrons in the strongly non-uniform (dipolar) magnetic field of the neutron star. We also explain, with less confidence, the variable MeV bump as the result of interaction of harder γ-rays with the power-law photons. The harder power law might be due to Compton scattering of relativistic electrons or photons.
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Wu, H., Y. Dai i M. D. Ding. "Highly Energetic Electrons Accelerated in Strong Solar Flares as a Preferred Driver of Sunquakes". Astrophysical Journal Letters 943, nr 1 (1.01.2023): L6. http://dx.doi.org/10.3847/2041-8213/acb0d1.
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Abstract Sunquakes are enhanced seismic waves excited in some energetic solar flares. Up to now, their origin has still been controversial. In this Letter, we select and study 20 strong flares in Solar Cycle 24, whose impulse phase is fully captured by the Reuven Ramaty High Energy Solar Spectroscopic Imager. For 11 out of 12 sunquake-active flares in our sample, the hard X-ray emission shows a good temporal and spatial correlation with the white-light enhancement and the sunquake. Spectral analysis also reveals a harder photon spectrum that extends to several hundred keV, implying a considerable population of flare-accelerated nonthermal electrons at high energies. Quantitatively, the total energy of electrons above 300 keV in sunquake-active flares is systematically different from that in sunquake-quiet flares, while the difference is marginal for electrons above 50 keV. All these facts support highly energetic electrons as a preferred driver of the sunquakes. Such an electron-driven scenario can be reasonably accommodated in the framework of a recently proposed selection rule for sunquake generation. For the remaining one event, the sunquake epicenter is cospatial with a magnetic imprint, i.e., a permanent change of magnetic field on the photosphere. Quantitative calculation shows that the flare-induced downward Lorentz force can do enough work to power the sunquake, acting as a viable sunquake driver for this specific event.