Soft X-ray Energy Research Articles

Effect of the axial magnetic field on a metallic gas-puff pinch implosion

The effect of an axial magnetic field Bz on an imploding metallic gas-puff Z-pinch was studied using 2D time-gated visible self-emission imaging. Experiments were performed on the IMRI-5 generator (450 kA, 450 ns). The ambient field Bz was varied from 0.15 to 1.35 T. It was found that the initial density profile of a metallic gas-puff Z-pinch can be approximated by a power law. Time-gated images showed that the magneto-Rayleigh–Taylor instabilities were suppressed during the run-in phase both without axial magnetic field and with axial magnetic field. Helical instability structures were detected during the stagnation phase for Bz < 1.1 T. For Bz = 1.35 T, the pinch plasma boundary was observed to be stable in both run-in and stagnation phases. When a magnetic field of 0.3 T was applied to the pinch, the soft x-ray energy was about twice that generated without axial magnetic field, mostly due to longer dwell time at stagnation.

THE MULTI-WAVELENGTH CHARACTERISTICS OF THE TeV BINARY LS I+61°303

ABSTRACT We study the characteristics of the TeV binary LS I+61°303 in radio, soft X-ray, hard X-ray, and gamma-ray (GeV and TeV) energies. The long-term variability characteristics are examined as a function of the phase of the binary period of 26.496 days as well as the phase of the superorbital period of 1626 days, dividing the observations into a matrix of 10 × 10 phases of these two periods. We find that the long-term variability can be described by a sine function of the superorbital period, with the phase and amplitude systematically varying with the binary period phase. We also find a definite wavelength-dependent change in this variability description. To understand the radiation mechanism, we define three states in the orbital/superorbital phase matrix and examine the wideband spectral energy distribution. The derived source parameters indicate that the emission geometry is dominated by a jet structure showing a systematic variation with the orbital/superorbital period. We suggest that LS I+61°303 is likely a microquasar with a steady jet.

A high-resolution x-ray spectrometer for a kaon mass measurement

The ASPECT consortium (Adaptable Spectrometer Enabled by Cryogenic Technology) is currently constructing a generalised cryogenic platform for cryogenic detector work which will be able to accommodate a wide range of sensors. The cryogenics system is based on a small mechanical cooler with a further adiabatic demagnetisation stage and will work with cryogenic detectors at sub-Kelvin temperatures. The commercial aim of the consortium is to produce a compact, user-friendly device with an emphasis on reliability and portability which can easily be transported for specialised on-site work, such as beam-lines or telescope facilities. The cryogenic detector platform will accommodate a specially developed cryogenic sensor, either a metallic magnetic calorimeter or a magnetic penetration-depth thermometer. The detectors will be designed to work in various temperatures regions with an emphasis on optimising the various detector resolutions for specific temperatures. One resolution target is of about 10eV at the energies range typically created in kaonic atoms experiments (soft x-ray energies). A following step will see the introduction of continuous, high-power, sub-Kelvin cooling which will bring the cryogenic basis for a high resolution spectrometer system to the market. The scientific goal of the project will produce an experimental set-up optimised for kaon-mass measurements performing high-resolution x-ray spectroscopy on a beam-line provided foreseeably by the J-PARC (Tokai, Japan) or DAΦNE (Frascati, Italy) facilities.

Long-term studies of the Cygnus Region and its objects: Cyg X-3 and γCygni SNR

The long-term studies of the Cygnus Region at energies 800 GeV - 100 TeV by SHALON telescope are presented in this paper. The results of twenty-year-long observations of the Cyg X-3 binary at energies 800 GeV - 85 TeV, detected by SHALON in 1995y are presented with images and integral spectra. The 4.8 hour orbital modulation of TeV γ-ray emission of Cyg X-3 was found in SHALON data. A number of high activity period of Cyg X-3 were detected at energies > 800 GeV during the all observation time. The correlation soft X-ray and TeV energy γ-ray fluxes is traced. Additional to Cyg X-3 study data on the TeV sources of Cygnus Region, namely γCygni SNR was obtained with SHALON.

Nanoscale characterization of local structures and defects in photonic crystals using synchrotron-based transmission soft X-ray microscopy.

For the structural characterization of the polystyrene (PS)-based photonic crystals (PCs), fast and direct imaging capabilities of full field transmission X-ray microscopy (TXM) were demonstrated at soft X-ray energy. PS-based PCs were prepared on an O2-plasma treated Si3N4 window and their local structures and defects were investigated using this label-free TXM technique with an image acquisition speed of ~10 sec/frame and marginal radiation damage. Micro-domains of face-centered cubic (FCC (111)) and hexagonal close-packed (HCP (0001)) structures were dominantly found in PS-based PCs, while point and line defects, FCC (100), and 12-fold symmetry structures were also identified as minor components. Additionally, in situ observation capability for hydrated samples and 3D tomographic reconstruction of TXM images were also demonstrated. This soft X-ray full field TXM technique with faster image acquisition speed, in situ observation, and 3D tomography capability can be complementally used with the other X-ray microscopic techniques (i.e., scanning transmission X-ray microscopy, STXM) as well as conventional characterization methods (e.g., electron microscopic and optical/fluorescence microscopic techniques) for clearer structure identification of self-assembled PCs and better understanding of the relationship between their structures and resultant optical properties.

Towards hybrid pixel detectors for energy-dispersive or soft X-ray photon science.

JUNGFRAU (adJUstiNg Gain detector FoR the Aramis User station) is a two-dimensional hybrid pixel detector for photon science applications at free-electron lasers and synchrotron light sources. The JUNGFRAU 0.4 prototype presented here is specifically geared towards low-noise performance and hence soft X-ray detection. The design, geometry and readout architecture of JUNGFRAU 0.4 correspond to those of other JUNGFRAU pixel detectors, which are charge-integrating detectors with 75 µm × 75 µm pixels. Main characteristics of JUNGFRAU 0.4 are its fixed gain and r.m.s. noise of as low as 27 e(-) electronic noise charge (<100 eV) with no active cooling. The 48 × 48 pixels JUNGFRAU 0.4 prototype can be combined with a charge-sharing suppression mask directly placed on the sensor, which keeps photons from hitting the charge-sharing regions of the pixels. The mask consists of a 150 µm tungsten sheet, in which 28 µm-diameter holes are laser-drilled. The mask is aligned with the pixels. The noise and gain characterization, and single-photon detection as low as 1.2 keV are shown. The performance of JUNGFRAU 0.4 without the mask and also in the charge-sharing suppression configuration (with the mask, with a `software mask' or a `cluster finding' algorithm) is tested, compared and evaluated, in particular with respect to the removal of the charge-sharing contribution in the spectra, the detection efficiency and the photon rate capability. Energy-dispersive and imaging experiments with fluorescence X-ray irradiation from an X-ray tube and a synchrotron light source are successfully demonstrated with an r.m.s. energy resolution of 20% (no mask) and 14% (with the mask) at 1.2 keV and of 5% at 13.3 keV. The performance evaluation of the JUNGFRAU 0.4 prototype suggests that this detection system could be the starting point for a future detector development effort for either applications in the soft X-ray energy regime or for an energy-dispersive detection system.

Data processing for soft X-ray diagnostics based on GEM detector measurements for fusion plasma imaging

The measurement system based on GEM – Gas Electron Multiplier detector is developed for X-ray diagnostics of magnetic confinement fusion plasmas. The Triple Gas Electron Multiplier (T-GEM) is presented as soft X-ray (SXR) energy and position sensitive detector. The paper is focused on the measurement subject and describes the fundamental data processing to obtain reliable characteristics (histograms) useful for physicists. So, it is the software part of the project between the electronic hardware and physics applications. The project is original and it was developed by the paper authors. Multi-channel measurement system and essential data processing for X-ray energy and position recognition are considered. Several modes of data acquisition determined by hardware and software processing are introduced. Typical measuring issues are deliberated for the enhancement of data quality. The primary version based on 1-D GEM detector was applied for the high-resolution X-ray crystal spectrometer KX1 in the JET tokamak. The current version considers 2-D detector structures initially for the investigation purpose. Two detector structures with single-pixel sensors and multi-pixel (directional) sensors are considered for two-dimensional X-ray imaging. Fundamental output characteristics are presented for one and two dimensional detector structure. Representative results for reference source and tokamak plasma are demonstrated.

X-ray Surveys of the Hot and Energetic Cosmos

AbstractA science meeting is an opportunity to exchange ideas with colleagues, to hear of new results and to learn from comprehensive reviews of a topic. Much of it happens in the meeting room and much of it also happens in the corridors of the meeting venue and in restaurants and perhaps bars near the meeting location. Its a combination of people and of place that is a bit [hard to predict] but when it goes well, you know it.All these elements came together for IAU Focus Meeting 6, X-ray Surveys of the Hot and Energetic Cosmos, in Honolulu last August. There are not many places more pleasant for an astronomical meeting than Hawaii, and the speakers did an outstanding job of reviewing the field and relaying the latest results.X-ray surveys have been a staple of astrophysics for nearly 50 years. There are large surveys and small, deep surveys and shallow, soft X-ray energies and hard. The combination gives us invaluable information about the hottest and/or most relativistic environments known. Theory helps us interpret the data in terms of the underlying physics. The heady combination of all of the above shaken and mixed in Hawaiian paradise has given us all a deeper understanding of the Universe. Please read on to see why.

Uniformity of Kilo-Pixel Arrays of Transition-Edge Sensors for X-ray Astronomy

We are developing kilo-pixel arrays of transition-edge sensor (TES) microcalorimeters for use in future laboratory and space based X-ray astrophysics experiments. These arrays are required to achieve an energy resolution of ΔE FWHM <; 3 eV full-width-half-maximum (FWHM) in the soft X-ray energy range. In this contribution we report on the development of 32 × 32 arrays of Mo/Au TESs with Bi/Au X-ray absorbers. We present measurements from 8 × 8 test arrays and 32 × 32 uniform arrays. Measurements of the bias point resistance and magnetic field dependence of the transition properties show that by carefully tuning the applied magnetic field the requirements on T C and magnetic field uniformity can be reduced whilst maintaining the target energy resolution. Results show ΔE FWHM ≈ 2.0 - 2.5 eV FWHM at a photon energy of 6 keV, measured across several pixels. Despite larger than typical T C variation across the detector, time division multiplexed readout of 30 common electrically biased pixels in the 32 × 32 array (in a 2 column × 16 row configuration) show an average ΔE FWHM = 3.0 ± 0.3 eV.

Multiedge X-ray Absorption Spectroscopy Part II: XANES Analysis of Bridging and Terminal Chlorides in Hexachlorodipalladate(II) Complex.

X-ray absorption spectroscopy is a unique experimental technique that can provide ground state electronic structure information about transition metal complexes with unoccupied d-manifold. The quantitative treatments of pre-edge and rising-edge features have already been developed for the sulfur- and chlorine-ligand K-edge excitations. The complementarity of using multiple core excitation edges from hard, tender, and soft X-ray energy regions has been defined for the first paper of this series. The given study provides compelling evidence for the transferability of the empirical transition dipole integral from ligand K-edge to metal L-edge and back to ligand K-edge in the tender X-ray energy range. The case study was performed for a series of homoleptic chloropalladium compounds at the chlorine K- and palladium L-edges. We propose the method described here to be generally applicable for other core level excitations, where complementarity of ground state electronic structural information from XANES analysis can provide the complete electronic structure description.

Study of structural and optical properties of zirconium carbide (ZrC) thin-films deposited by ion beam sputtering for soft x-ray optical applications

Compound materials have shown stable and enhanced optical performance in soft x-ray energy region. However, the growth related change in structural and chemical properties lead to affect their performances. In the present study, thin films of different thicknesses of ZrC compound material were deposited on Si (100) substrate. Optical response of ZrC thin film was measured in soft x-ray energy region using Indus-1 reflectivity beamline. It was found that the soft x-ray reflectivity data of ZrC thin films cannot be explained with Henke's tabulated data. To understand this disagreement a detailed structural and chemical investigation was carried out using x-ray reflectivity, grazing incidence x-ray diffraction, atomic force microscopy and x-ray photoelectron spectroscopy techniques. It was found that the presence of unreacted carbon along with small oxygen in ZrC matrix is responsible for variation in optical constant value. Details of the investigations are discussed.

A SEARCH FOR FAST X-RAY VARIABILITY FROM ACTIVE GALACTIC NUCLEI USINGSWIFT

Blazars are a class of active galactic nuclei (AGNs) known for their very rapid variabilty in the high energy regions of the electromagnetic spectrum. Despite this known fast variability, X-ray observations have generally not revealed variability in blazars with rate doubling or halving timescales less than approximately 15 min. Since its launch, the Swift X-ray Telescope has obtained 0.2-10 keV X-ray data on 143 AGNs, including blazars, through intense target of opportunity observations that can be analyzed in a multiwavelength context and used to model jet parameters, particularly during flare states. We have analyzed this broad Swift data set in a search for short timescale variability in blazars that could limit the size of the emission region in the blazar jet. While we do find several low-significance possible flares with potential indications of rapid variability, we find no strong evidence for rapid ($<$15 minutes) doubling or halving times in flares in the soft X-ray energy band for the AGNs analyzed.

Overview of nanoscale NEXAFS performed with soft X-ray microscopes.

Today, in material science nanoscale structures are becoming more and more important. Not only for the further miniaturization of semiconductor devices like carbon nanotube based transistors, but also for newly developed efficient energy storage devices, gas sensors or catalytic systems nanoscale and functionalized materials have to be analysed. Therefore, analytical tools like near-edge X-ray absorption fine structure (NEXAFS) spectroscopy has to be applied on single nanostructures. Scanning transmission X-ray microscopes (STXM) as well as full-field transmission X-ray microscopes (TXM) allow the required spatial resolution to study individual nanostructures. In the soft X-ray energy range only STXM was used so far for NEXAFS studies. Due to its unique setup, the TXM operated by the Helmholtz-Zentrum Berlin (HZB) at the electron storage ring BESSY II is the first one in the soft X-ray range which can be used for NEXAFS spectroscopy studies which will be shown in this review. Here we will give an overview of the different microscopes used for NEXAFS studies and describe their advantages and disadvantages for different samples.

Development of Array Detectors with Three-Dimensional Structure toward 1000 Pixels of Superconducting Tunnel Junctions

Superconducting tunnel junction (STJ) array detectors can exhibit excellent performance with respect to energy resolution, detection efficiency, and counting rate in the soft X-ray energy range, by which those excellent properties STJ array detectors are well suited for detecting X-rays at synchrotron radiation facilities. However, in order to achieve a high throughput analysis for trace impurity elements such as dopants in structural or functional materials, the sensitive area of STJ array detectors should be further enlarged up to more than 10 times larger by increasing the pixel number in array detectors. In this work, for a large STJ-pixel number of up to 1000 within a 10 mm- square compact chip, we have introduced three-dimensional (3D) structure by embedding a wiring layer in a SiO2 isolation layer underneath a base electrode layer of STJs. The 3D structure is necessary for close-packed STJ arrangement, avoiding overlay of lead wiring, which is common in conventional two-dimensional layout. The fabricated STJ showed excellent current-voltage characteristics having low subgap currents less than 2 nA, which are the same as those of conventional STJs. An STJ pixel has an energy resolution of 31 eV (FWHM) for C-Kα (277 eV).

Band Structure Analysis of La0.7Sr0.3MnO3Perovskite Manganite Using a Synchrotron

Oxide semiconductors and their application in next-generation devices have received a great deal of attention due to their various optical, electric, and magnetic properties. For various applications, an understanding of these properties and their mechanisms is also very important. Various characteristics of these oxides originate from the band structure. In this study, we introduce a band structure analysis technique using a soft X-ray energy source to study aLa0.7Sr0.3MnO3(LSMO) oxide semiconductor. The band structure is formed by a valence band, conduction band, band gap, work function, and electron affinity. These can be determined from secondary electron cut-off, valence band spectrum, O 1s core electron, and O K-edge measurements using synchrotron radiation. A detailed analysis of the band structure of the LSMO perovskite manganite oxide semiconductor thin film was established using these techniques.

DIFFUSE X-RAY EMISSION FROM THE SUPERBUBBLES N70 AND N185 IN THE LARGE MAGELLANIC CLOUD

We present a study of the diffuse X-ray emission from superbubbles N 70 (DEM L301) and N 185 (DEM L25) located in the Large Magellanic Cloud, based on data from the XMM-Newton Satellite. We obtained spectra and images of these objects in the soft X-ray energy band. These X-ray spectra were fitted by a thermal plasma model, with temperatures of $2.6 \times 10^{6}$ K and $2.3 \times 10^{6}$ K, for N 70 and N 185, respectively. For N 70, images show that X-ray emission comes from the inner regions of the superbubble, when we compare the distribution of the X-ray and the optical emission; while for N 185, the X-ray emission is partially confined by the optical shell. We suggest that the observed X-ray emission is caused by shock-heated gas, inside of the optical shells. We also obtained X-ray luminosities which exceed the values predicted by the standard analytical model. This fact shows that, in addition to the winds of the interior stars, it is necessary to consider another ingredient in the description, such as a supernova explosion, as has been proposed in previous numerical models.

Note: Effect of photodiode aluminum cathode frame on spectral sensitivity in the soft x-ray energy band.

Silicon photodiodes used for soft x-ray detection typically have a thin metal electrode partially covering the active area of the photodiode, which subtly alters the spectral sensitivity of the photodiode. As a specific example, AXUV4BST photodiodes from International Radiation Detectors have a 1.0 μm thick aluminum frame covering 19% of the active area of the photodiode, which attenuates the measured x-ray signal below ~6 keV. This effect has a small systematic impact on the electron temperature calculated from measurements of soft x-ray bremsstrahlung emission from a high-temperature plasma. Although the systematic error introduced by the aluminum frame is only a few percent in typical experimental conditions on the Madison Symmetric Torus, it may be more significant for other instruments that use similar detectors.

Development of an in-vacuum diffractometer for resonant soft X-ray scattering

Resonant soft X-ray scattering measurements become one of powerful techniques to probe charge, orbital and spin orderings in strongly correlated electron systems. We have developed new in-vacuum diffractometer with a large vacuum chamber to solve experimental limitations of in-vacuum measurement in soft X-ray energy region, and for future instrumental developments. In this paper, the features of the diffractometer are presented.

Toward 1000-Pixel Superconducting-Tunnel-Junction Detectors for X-Ray Absorption Fine Structure Spectroscopy

Superconducting tunnel junction (STJ) detectors have excellent energy resolution, high detection efficiency, and high counting rate in the soft X-ray energy range. These properties are suitable for synchrotron radiation facilities. However, in order to achieve a high throughput analysis for dopants with a lower concentration, the pixel number of STJ array detectors should be further increased to enlarge the sensitive area. As a first step, we have fabricated 400-pixel STJ array detectors and checked the operation yield and the uniformity of leakage current (\(I_{leak}\)) values. Fabricated STJs showed excellent current-voltage curves having low subgap current. The operation yield of STJs with \(I_{leak}\) values of less than 10 nA was 96 \(\%\). The average \(I_{leak}\) of 3.6 nA is roughly equivalent to that of the 100-pixel STJ array detector, which is open to users at synchroton radiation beam lines and have 12 eV energy resolution at 400 eV.

Exceptional behavior of d-like surface resonances on W(110): the one-step model in its density matrix formulation

Spin–orbit-induced spin splitting of surface states has attracted great interest in recent years because of the high potential for technological applications associated with this phenomenon. This Rashba physics is found in a variety of systems ranging from simple metals like Ag or Au to the so-called topological insulators which are of special interest in spintronics. A very special and unique case is found at the W(110) surface. In this metal d-like surface resonances exhibit energy dispersions and spin-polarization structures which are reminiscent of topological surface states. In our theoretical study, we present a complete analysis of the surface electronic structure of W(110) and show that the atypical linear-shaped dispersion behavior is triggered by the amount of charge transfer from the bulk into the first few vacuum layers. Furthermore, we compare our theoretical spectra with experimental photoemission data on W(110) and demonstrate that our state-of-the-art photoemission theory is able to deal with these peculiar surface features in a quantitative way. Our analysis is based on a generalization of the relativistic one-step model of photoemission, recently extended by us to study photoelectron spectroscopy at high photon energies. This theoretical approach was realized in the full spin-density matrix formulation for the photocurrent, which allows for an unrestricted calculation of the spin-polarization vector of the photoelectron. As an additional result we predict very peculiar behavior of these surface features showing up even at soft and hard x-ray energies. This observation is very surprising, unprecedented for ordinary surface features on simple metal surfaces.