X-ray Emission Measurements Research Articles

Design and performance of a versatile curved-crystal spectrometer for high-resolution spectroscopy in the tender x-ray range

A complete in-vacuum curved-crystal x-ray emission spectrometer in Johansson geometry has been constructed for a 2-6 keV energy range with sub natural line-width energy resolution. The spectrometer is designed to measure x-ray emission induced by photon and charged particle impact on solid and gaseous targets. It works with a relatively large x-ray source placed inside the Rowland circle and employs position sensitive detection of diffracted x-rays. Its compact modular design enables fast and easy installation at a synchrotron or particle accelerator beamline. The paper presents main characteristics of the spectrometer and illustrates its capabilities by showing few selected experimental examples.

Specific features of thermocouple calorimeter application for measurements of pulsed X-ray emission from plasma

It is shown that the accuracy of time-integrated measurements of pulsed X-ray emission from hot plasma with calibrated thermocouple calorimeters is mainly determined by two factors. The first and the most important factor is heating of the filter by the absorbed X-rays; as a result, the calorimeter measures the thermal radiation of the filter, which causes appreciable distortion of the temporal profile and amplitude of the recorded signal. The second factor is the dependence of the effective depth of X-ray absorption in the dielectric that covers the entrance window of the calorimeter on the energy of X-ray photons, i.e., on the recorded radiation spectrum. The results of model calculations of the calorimeter signal are compared with the experimental data.

超强激光脉冲作用下的Au等离子体L-X射线辐射测量

超强激光脉冲作用下的Au等离子体L-X射线辐射测量

Measurements of hard x-ray emission from runaway electrons in DIII-D

The spatial distribution of runaway electron (RE) strikes to the wall during argon pellet-initiated rapid shutdown of diverted and limited plasma shapes in DIII-D is studied using a new array of hard x-ray (HXR) scintillators. Two plasma configurations were investigated: an elongated diverted H-mode and a low-elongation limited L-mode. HXR emission from MeV level REs generated during the argon pellet injection is observed during the thermal quench (TQ) in diverted discharges from REs lost into the divertor. In limiter discharges, this prompt TQ loss is reduced, suggesting improved TQ confinement of REs in this configuration. During the plateau phase when the plasma current is carried by REs, toroidally symmetric HXR emission from remaining confined REs is seen. Transient HXR bursts during this RE current plateau suggest the presence of a small level of wall losses due to the presence of an unidentified instability. Eventually, an abrupt final loss of the remaining RE current occurs. This final loss HXR emission shows a strong toroidal peaking and a consistent spatiotemporal evolution that suggests the development of a kink instability.

In vitro evidence of dysregulation of blood–brain barrier function after acute and repeated/long-term exposure to TiO 2 nanoparticles

The effects of titanium dioxide nanoparticles (TiO 2 NPs) on blood–brain barrier (BBB) function are unknown. Here, we report such evidence of adverse effects after in vitro exposure of a rat primary cell-based BBB model to NPs. BBB integrity was studied by measuring the flux of sucrose through the monolayer. P-glycoprotein (P-gp) activity was assessed by measuring the passage of vinblastine. Transcription profiles of P-gp and other ABC transporters as well as of cytokines were investigated by real-time PCR. Electron microscopy and particle-induced X-ray emission measurements were performed. We compared several exposure modalities, from early to chronic, mimicking a brain-to-blood transport or a systemic contamination. In the first case, BBB integrity was preserved, but P-gp activity of endothelial cells (BECs) was reduced. In the second case, BBB integrity and P-gp function were impaired from 5 μg/mL for 24 h and expression of tight junction proteins and efflux transporters was modulated. An inflammatory response had repercussions on ABC transporter expression of glial cells. We demonstrate that NPs accumulated in BECs and crossed the cell monolayer. These findings suggest that there is an immunoregulatory loop between inflammatory components, BECs and glial cells in the dysfunction of the BBB during exposure to TiO 2 NPs.

Slowly rotating black holes in alternative theories of gravity

We present, in closed analytic form, a general stationary, slowly rotating black hole, which is solution to a large class of alternative theories of gravity in four dimensions. In these theories, the Einstein-Hilbert action is supplemented by all possible quadratic, algebraic curvature invariants coupled to a scalar field. The solution is found as a deformation of the Schwarzschild metric in General Relativity. We explicitly derive the changes to the orbital frequency at the innermost stable circular orbit and at the light ring in closed form. These results could be useful when comparing General Relativity against alternative theories by (say) measurements of X-ray emission in accretion disks, or by stellar motion around supermassive black holes. When gravitational-wave astronomy comes into force, strong constraints on the coupling parameters can in principle be made.

Orbital anisotropy and low-energy excitations of the quasi-one-dimensional conductorβ-Sr0.17V2O5

The electronic structure of the quasi-one-dimensional vanadium beta-bronze \ensuremath{\beta}-Sr${}_{0.17}$V${}_{2}$O${}_{5}$ has been measured in detail using soft x-ray absorption spectroscopy, x-ray emission spectroscopy, and resonant inelastic soft x-ray scattering. Together, these measurements have been used to derive the experimental site-resolved ($k$-integrated) band structure of a material whose electronic structure is difficult to obtain from first principles. The occupied states, probed by x-ray emission measurements, demonstrate the O 2$p$--V 3$d$ bonding hybridization at the bottom of the O 2$p$ band, with the V 3${d}_{xy}$ ``magnetic orbitals'' well separated in energy. These results are consistent with the carriers being small polarons. The strong anisotropy in the absorption spectrum is used to identify the energy and character of the unoccupied states. Additionally, absorption measurements at the V $L$-edge are compared with atomic multiplet calculations, clarifying the interpretation of the experimental multiplet structure and consistent with the presence of both V${}^{5+}$ and V${}^{4+}$ species. Site-specific electronic excitations, probed by resonant inelastic x-ray scattering at the V $L$-edge, are observed at an energy of 1.1 eV, and are suggested to correspond to transitions from the partially filled ${d}_{xy}$ magnetic orbital into the unoccupied ${d}_{xy,yz}$ orbitals.

Origin of step-like behavior in the Co/Si system

A systematic investigation of the structure, nature of the interface and theirpossible connections with magnetic properties for the as-deposited Co/Si/Cotrilayer system has been carried out. X-ray reflectivity, cross-sectional transmissionelectron microscopy and x-ray emission measurements performed on theCo/Si/Co trilayer system show that when the Si layer thickness is less than ∼ 20 Å, the full Si layer is converted into a cobalt silicide layer whereas when the Si layer thickness > 20 Å along with the silicide layer. the pure Si layer also remains. A comparison of magneto-opticalKerr effect and magnetoresistance measurements reveals the absence of antiferromagneticcoupling in these samples. Double-step-like magnetization, in the case of Si layer thickness > 20 Å between two Co layers, is explained by magnetization reversal of two ferromagnetic layershaving different coercivities, independent of each other.

X-Ray Measurement and Enhancement of SBUPF1 Plasma Focus Device in Different Ar Pressures and Operating Voltages

In this paper, best condition of filling gas pressure and operating voltage for SBUPF1 plasma focus device to have maximum intensity of hard and soft X-ray emission has been reported. For time resolved X-ray detection, PIN detector and fast plastic Scintillator detector with appropriate filters have been used and for time integrated X-ray emission measurement, radiography films with appropriate filter masks have been used. Rogowski coil has been used for pinch detection. The highest hard X-ray emission has been observed at the pressure of 0.45 mbar of Argon and discharge voltage about 23.5 kV. The highest Soft X-ray emission has been observed at the pressure of 0.35 mbar of Argon and discharge voltage about 23.5 kV. For enhancement of hard X-ray emission intensity, lead disk was placed in copper anode tip and measurements were repeated. Results have shown that hard X-ray emission has been enhanced about 23% and soft X-ray emission has been enhanced about 33% with inserting a high atomic number metal disk like lead. Results from integral X-ray measurement have shown presence of dominant peaks in ranges 13.2–15, 21–21.9 and 23.4–24.3 keV with significant spectral components in the range of 0–50 keV. Pinch size has measured with pin hole camera and it is about 0.6 mm × 2.12 mm. Captured images with SBUPF1 have confirmed that it is a suitable source for introspective imaging with capability of showing very fine details.

Side-chain effects on electronic structure and molecular stacking arrangement of PCBM spin-coated films

The electronic structure and molecular stacking arrangement of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was studied using a combination of near-edge X-ray absorption fine structure measurements and density functional theory calculations. Measurements show that the side chain lifts the energy degeneracy of the C60 molecular orbitals around the chain attachment. This breaks the orbital symmetry of the LUMO of the C60 backbone which is observed through polarization dependence of C 1s→π∗ transitions. This dependence is analyzed to determine the bulk crystal structure of PCBM. X-ray emission and absorption measurements indicate the band gap energy of PCBM to be 1.87eV.

Progress of in-air microbeam system at the Wakasa Wan Energy Research Center

Modifications of an in-air microbeam system at the Wakasa Wan Energy Research Center designed to improve its performance are described. In the previous setup, a silicon nitride membrane (area: 1×1mm2; thickness: 100nm) was used for the beam exit window and the distance between the window and the sample was restricted to ⩾1.7mm. Due to this restriction, the beam spot size obtained using the previous setup was 13×13μm2. To reduce the beam spot size, the beam exit window was replaced by a silicon nitride membrane (area: 3 (horizontal)×2 (vertical)mm2; thickness: 200nm). In this setup, the sample can be moved as close as 0.7mm to the window, enabling a beam spot size of 7×6μm2 to be achieved. An additional Si-PIN X-ray detector was installed to estimate the relative number of beam particles. It detects X-rays from the beam exit window. The number of the X-rays from the beam exit window (which is proportional to the number of beam particles) is used for quantitative analysis and for online monitoring of the beam current. This system has the potential to be used for simultaneous particle-induced X-ray emission (PIXE) and particle-induced gamma-ray emission (PIGE) measurements and for studying dental medicine.

Equilibrium reconstruction for single helical axis reversed field pinch plasmas

Single helical axis configurations are emerging as the natural state for high-current reversed field pinch plasmas. These states feature the presence of transport barriers in the core plasma. Here we present a method for computing the equilibrium magnetic surfaces for these states in the force-free approximation, which has been implemented in the SHEq code. The method is based on the superposition of a zeroth-order axisymmetric equilibrium and of a first-order helical perturbation computed according to Newcomb's equation supplemented with edge magnetic field measurements. The mapping of the measured electron temperature profiles, soft x-ray emission and interferometric density measurements on the computed magnetic surfaces demonstrates the quality of the equilibrium reconstruction. The procedure for computing flux surface averages is illustrated, and applied to the evaluation of the thermal conductivity profile. The consistency of the evaluated equilibria with Ohm's law is also discussed.

Detection of x-ray emission in a nanosecond discharge in air at atmospheric pressure

Measurement of x-ray emission is an important parameter to investigate runaway behavior of fast electrons produced in nanosecond-pulse gas discharge. An online detection system of x rays is described in this paper, and the system consists of an x-ray detector with NaI (Tl) scintillator and photomultiplier tube, and an integrated multichannel analyzer. The system is responsible for detecting x-ray emission signal, processing the detected signals, and scaling the energy distribution. The calibration results show that every channel of the detection system represents a given x-ray energy and various x rays can be divided into different energy ranges between 10 and 130 keV. For a repetitive nanosecond-pulse breakdown between highly nonuniform gaps in open air, an energy distribution is obtained using the online detection system. It shows that the x-ray emission is a continuous spectrum and the x rays of above 60 keV dominate in the detected energy distribution.

Scaling Hot-Electron Generation to High-Power, Kilojoule-Class Laser-Solid Interactions

Thin-foil targets were irradiated with high-power (1 ≤ P(L) ≤ 210 TW), 10-ps pulses focused to intensities of I>10(18) W/cm(2) and studied with K-photon spectroscopy. Comparing the energy emitted in K photons to target-heating calculations shows a laser-energy-coupling efficiency to hot electrons of η(L-e) = 20 ± 10%. Time-resolved x-ray emission measurements suggest that laser energy is coupled to hot electrons over the entire duration of the incident laser drive. Comparison of the K-photon emission data to previous data at similar laser intensities shows that η(L-e) is independent of laser-pulse duration from 1 ≤ τ(p) ≤ 10 ps.

The contribution of star-spots to coronal structure

Significant progress has been made recently in our understanding of the structure of stellar magnetic fields, thanks to advances in detection methods such as Zeeman-Doppler Imaging. The extrapolation of this surface magnetic field into the corona has provided 3D models of the coronal magnetic field and plasma. This method is sensitive mainly to the magnetic field in the bright regions of the stellar surface. The dark (spotted) regions are censored because the Zeeman signature there is suppressed. By modelling the magnetic field that might have been contained in these spots, we have studied the effect that this loss of information might have on our understanding of the coronal structure. As examples, we have chosen two stars (V374 peg and AB Dor) that have very different magnetograms and patterns of spot coverage. We find that the effect of the spot field depends not only on the relative amount of flux in the spots, but also its distribution across the stellar surface. For a star such as AB Dor with a high spot coverage and a large polar spot, at its greatest effect the spot field may almost double the fraction of the flux that is open (hence decreasing the spindown time) while at the same time increasing the X-ray emission measure by two orders of magnitude and significantly affecting the X-ray rotational modulation.

Rigid Field Hydrodynamic simulations of the magnetosphere of σ Orionis E

AbstractWe present Rigid Field Hydrodynamic simulations of the magnetosphere of σ Ori E. We find that the X-ray emission from the star's magnetically confined wind shocks is very sensitive to the assumed mass-loss rate. To compare the simulations against the measured X-ray emission, we first disentangle the star from its recently discovered late-type companion using Chandra HRC-I observations. This then allows us to place an upper limit on the mass-loss rate of the primary, which we find to be significantly smaller than previously imagined.

NONTHERMAL PROPERTIES OF SUPERNOVA REMNANT G1.9+0.3

The properties of the - presumably - youngest Galactic supernova remnant (SNR) G1.9+0.3 are investigated within the framework of nonlinear kinetic theory of cosmic ray acceleration in SNRs. The observed angular size and expansion speed as well as the radio and X-ray emission measurements are used to determine relevant physical parameters of this SNR. Under the assumption that SNR G1.9+0.3 is the result of a Type Ia supernova near the Galactic center (at the distance d=8.5 kpc) the nonthermal properties are calculated. In particular, the expected TeV gamma-ray spectral energy density is predicted to be as low as $\epsilon_{\gamma}F_{\gamma} \approx 5\times 10^{-15}$ erg cm$^{-2}$ s$^{-1}$, strongly dependent ($F_{\gamma}\propto d^{-11}$) upon the source distance d.

Energies and widths of atomic core-levels in liquid mercury

High-resolution measurements of the photoinduced X-ray emission of liquid mercury were performed, using a transmission DuMond-type crystal spectrometer for transitions above 11 keV and a reflection von Hamos-type crystal spectrometer for transitions below 11 keV. The target X-ray fluorescence was produced by irradiating the sample with the Bremsstrahlung from X-ray tubes. The energies and natural linewidths of 6 K-shell, 26 L-shell and 2 M-shell X-ray transitions were determined. Using a least-squares-fit method to solve the two sets of equations derived from the observed transition energies and transition widths the binding energies of the subshells K to M5 and O1 and the level widths of the subshells K to N5 and O1 could also be determined.

SYNCHROTRON CONSTRAINTS ON A HYBRID COSMIC-RAY AND THERMALLY DRIVEN GALACTIC WIND

Cosmic rays and magnetic fields can substantially impact the launching of large-scale galactic winds. Many researchers have investigated the role of cosmic rays; our group previously showed that a cosmic-ray and thermally-driven wind could explain soft X-ray emission towards the center of the Galaxy. In this paper, we calculate the synchrotron emission from our original wind model and compare it to observations; the synchrotron data shows that earlier assumptions about the launching conditions of the wind must be changed: we are required to improve that earlier model by restricting the launching region to the domain of the inner "Molecular Ring", and by decreasing the magnetic field strength from the previously assumed maximum strength. With these physically-motived modifications, we find that a wind model can fit both the radio synchrotron and the X-ray emission, although that model is required to have a higher gas pressure and density than the previous model in order to reproduce the observed X-ray emission measure within the smaller `footprint'. The drop in magnetic field also decreases the effect of cosmic-ray heating, requiring a higher temperature at the base of the wind than the previous model.

Properties of Gd 2O 3:Eu 3+, Tb 3+ nanopowders obtained by sol–gel process

A significant practical application for nanostructured materials is X-ray medical imagery, because it is necessary to use dense materials in order to enable absorption of high energy photons. An important requirement of these materials is UV–vis range emission produced by X-ray excitation, which can be influenced by the particle size. Europium doped gadolinium oxide is a well known red phosphor. Moreover, nanophosphors of Gd 2O 3 codoped with Tb 3+, Eu 3+ increase their light yield by energy transfer between Tb 3+ and Eu 3+. In this study, Gd 2O 3 nanopowders codoped with Eu 3+ and Tb 3+ (2.5 at.% Eu 3+, and 0.005 and 0.01 at.% Tb 3+) were obtained via a sol–gel process using gadolinium pentanedionate as precursor and europium and terbium nitrates as doping sources. In this paper, we report the influence of annealing temperature on the structure, morphology and luminescent properties of Gd 2O 3:Eu 3+, Tb 3+ by means of TGA, XRD, TEM and X-ray emission measurements.