Soft X-ray Emission Research Articles

Time resolved and time integrated analysis of the AXUV photodiode diagnostics for EUV and soft X-ray emission of nanosecond-laser-produced plasma

This paper addresses the experimental results and analysis of the time-resolved and time-integrated of AXUV (absolute extreme ultraviolet) photodiode diagnostics. These results are obtained by the measurement of EUV and soft X-ray (SX) power radiation of plasma-produced under the interaction of laser pulse (intensity ∼5 × 1011 W/cm2, pulse durations in the range of 10−30 ns and wavelength 1064 nm) with one steel-316 target. The EUV and SX signals with the three specific peaks are detected by AXUV photodiode. From the analysis of time resolved of the AXUV signal, it is inferred that the first signal peak can dominantly be related to the free-free transition mechanism of radiation and also the latter related to the free-band and bond-bond transitions respectively. The energy of EUV and SX pulse emission is observed to be approximately linear, proportional to the laser pulse energy. The time integrated results show that, the average energy conversion efficiency is determined to be about 3.7 %.

Design and construction of the x-ray instrumentation onboard the HaloSat CubeSat

HaloSat is the first mission funded by NASA’s Astrophysics Division to use the CubeSat platform. Using three co-aligned silicon drift detectors, the HaloSat observatory measures soft (0.4 to 7 keV) x-ray emission from sources of diffuse emission such as the hot, gaseous halo of the Milky Way. We describe the design and construction of the science payload on HaloSat and the reasoning behind many of the choices. As a direct result of the design choices and adherence to best practices during construction, the HaloSat science payload continues to perform well after more than one year on-orbit.

Final Spitzer IRAC Observations of the Rise and Fall of SN 1987A

Abstract Spitzer's final Infrared Array Camera observations of SN 1987A show the 3.6 and 4.5 μm emission from the equatorial ring (ER) continues a period of steady decline. Deconvolution of the images reveals that the emission is dominated by the ring, not the ejecta, and is brightest on the west side. Decomposition of the marginally resolved emission also confirms this, and shows that the west side of the ER has been brightening relative to the other portions of the ER. The infrared morphological changes resemble those seen in both the soft X-ray emission and the optical emission. The integrated ER light curves at 3.6 and 4.5 μm are more similar to the optical light curves than the soft X-ray light curve, though differences would be expected if dust is responsible for this emission and its destruction is rapid. Future observations with the James Webb Space Telescope will continue to monitor the ER evolution, and will reveal the true spectrum and nature of the material responsible for the broadband emission at 3.6 and 4.5 μm. The present observations also serendipitously reveal a nearby variable source, subsequently identified as a Be star, that has gone through a multiyear outburst during the course of these observations.

Using the Modified Lee Model Code to Calculate the Optimum Length of NiZn Ferrite to Enhance the DPF Argon SXR Emission

A modified version of the Lee Model Code with better calculation of the magnetic field inside the Dense Plasma Focus (DPF) tube has been used to investigate the NiZn ferrite effect on the Amirkabir Plasma Focus (APF) machine behavior. It has been explained how various lengths of the ferrite can affect the discharge current trace.The minimum ferrite length which had sensible effects on APF working in 10 kV filled with 0.1-Torr argon has been determined. Regarding the optimum conditions for energy-transfer and argon Soft X-Ray (SXR) emission, the optimum length of the NiZn ferrite has been calculated for various charging voltages and pressures and a scaling-law curve has been presented. Measurements have proved increase in the SXR emission by employing ferrites.

Inferred UV fluence focal-spot profiles from soft x-ray pinhole-camera measurements on OMEGA.

A method was developed with laser-irradiated Au planar foils to characterize the focal spot of UV laser beams on a target at full energy from soft x-ray emission. A pinhole camera with a back-thinned charge-coupled device detector and filtration with thin Be and Al foil filters provides images of the x-ray emission at photon energies <2 keV. This method requires a careful measurement of the relationship between the applied UV fluence and the x-ray signal, which can be described by a power-law dependence. The measured exponent γ ∼ 2 provides a dynamic range of ∼25 for the inferred UV fluence. UV fluence profiles of selected beams were measured for 100-ps and 1-ns laser pulses and were compared to directly measured profiles from an UV equivalent-target-plane diagnostic. The inferred spot size and super-Gaussian order from the x-ray technique agree within several percent with the values measured with the direct UV measurements.

Effects of HF on the Lithiation Behavior of the Silicon Anode in LiPF6 Organic Electrolyte Solution.

As one of the major impurities in the organic electrolyte, HF can react with the alkali components in the solid electrolyte interphase (SEI), such as lithium alkoxide and lithium carbonate, to form more LiF-rich SEI. Here, the effects of HF on the lithiation behavior of the single crystal Si(111) anode were studied using scanning electron microscopy, soft X-ray emission spectroscopy, and windowless energy-dispersive X-ray spectroscopy. When the Li–Si alloy is formed in 1.0 M LiPF6 in the propylene carbonate solvent, it has a layered structure that contained the first layer of crystalline Li15Si4 (c-Li15Si4) alloy pyramids, the second layer of amorphous Li13Si4 (a-Li13Si4) alloy, and a third layer of Li-diffused LixSi alloy. When the more concentrated HF is in the electrolyte solution, less amount of the c-Li15Si4 alloy is formed in the first layer. It suggests that the Si lithiation can form only amorphous LixSi alloy relative to the components in the electrolytes. The study also explains why only amorphous LixSi alloy formation was observed in some previous studies.

In-situ/operando soft x-ray spectroscopy characterization of energy and catalytic materials

The capabilities of soft x-ray absorption (XAS), soft x-ray emission spectroscopy (XES), resonant inelastic soft x-ray scattering (RIXS), and their application to characterization of solar energy materials are presented. We have discussed some recent developments of in-situ soft x-ray spectroscopy cells, which enable the investigation of critical solid/liquid or solid/gas interfaces in chemical and electrochemical processes under real-world practical conditions. In particular, in-situ soft x-ray spectroscopies can be utilized to probe the formation of intermediate species, charge separation upon illumination of sunlight and electron transfer to the interfacial reactions. A number of examples using soft x-ray spectroscopies to study these solar energy and catalytic materials are discussed to demonstrate how these powerful characterization tools could be helpful to further understand the energy conversion and energy storage systems.

The nuclear region of NGC 613 – I. Multiwavelength analysis

ABSTRACT In this paper, we report a detailed study with a variety of data from optical, near-infrared, X-ray, and radio telescopes of the nuclear region of the galaxy NGC 613 with the aim of understanding its complexity. We detected an extended stellar emission in the nucleus that, at first, appears to be, in the optical band, two stellar nuclei separated by a stream of dust. The active galactic nucleus (AGN) is identified as a variable point-like source between these two stellar components. There is a central hard X-ray emission and an extended soft X-ray emission that closely coincides with the ionization cone, as seen in the [O iii]λ5007 emission. The centroid of the [O i]λ6300 emission does not coincide with the AGN, being shifted by 0.24 arcsec towards the ionization cone; this shift is probably caused by a combination of differential dust extinction together with emission and reflection in the ionization cone. The optical spectra extracted from the central region are typical of low-ionization nuclear emission-line regions. We also identify 10 H ii regions, eight of them in a star-forming ring that is visible in Br γ, [Fe ii]λ16436, and molecular CO(3-2) images observed in previous studies. Such a ring also presents weak hard X-ray emission, probably associated with supernova remnants, not detected in other studies. The position of the AGN coincides with the centre of a nuclear spiral (detected in previous works) that brings gas and dust from the bar to the nucleus, causing the high extinction in this area.

Interface Formation between CdS and Alkali Postdeposition-Treated Cu(In,Ga)Se2 Thin-Film Solar Cell Absorbers-Key To Understanding the Efficiency Gain.

A combination of X-ray photoelectron/Auger electron spectroscopy and soft X-ray emission spectroscopy has been employed to investigate the impact of different alkali postdeposition treatments (PDTs) on the chemical structure of the (buried) CdS/Cu(In,Ga)Se2 heterojunction: the key interface in chalcopyrite-based thin-film solar cells. Chemical bath deposited (CBD) CdS layers of different thicknesses on NaF PDT (CIGSeNaF) and NaF + KF PDT (CIGSeNaF+KF) Cu(In,Ga)Se2 absorbers prepared at low temperature (to facilitate the use of flexible, e.g., polyimide, substrates) were studied. While we find the CdS/CIGSeNaF interface to be mainly free of significant chemical interaction, in the proximity of the CdS/CIGSeNaF+KF interface, an elemental redistribution involving Cd, In, K, S, and Se is revealed. For the early stages of the CBD-CdS process, our findings are in agreement with the conversion of the K-In-Se-type layer present on the CIGSeNaF+KF surface into a mixed Cd-In-(O,OH,S,Se)-type layer, probably having some Cd-In and (S,O)-Se composition gradients. For long CBD times-independent of employed PDT-we find the buffer material to be best described by a Cd(O,OH,S)-like species rather than by a pure CdS buffer. These findings shed light on the observed performance leap of corresponding CdS/CIGSeNaF+KF-based solar cells.

A NuSTAR view of GRS 1716−249 in the hard and intermediate states

ABSTRACT We present a detailed analysis of the spectral properties of the black hole transient GRS 1716−249, based on the archival Swift and NuSTAR observations taken during the outburst of this source in 2016–2017. The first six NuSTAR observations show that the source is in a canonical hard state, where the spectrum is dominated by a power-law continuum. The seventh NuSTAR observation is taken during the intermediate state where both a disc thermal component and a power-law continuum are shown. All of our observations show a broad emission-line feature in the iron band and a Compton hump above 10 keV. We model the broad-band spectra using a high-density disc reflection model, where the soft X-ray emission in the hard state is interpreted as part of the disc reflection component. This model enables us to constrain the disc density parameter of GRS 1716−249 in the range of 1019–1020 cm−3. We only obtain an upper limit of the inner disc radius using high-density disc reflection spectroscopy and the results indicate either a non-truncated disc or a slightly truncated disc with Rin ≲ 20 rg.

Multiple Temperature Components of the Hot Circumgalactic Medium of the Milky Way

Abstract We present a deep XMM-Newton observation of the Galactic halo emission in the direction of the blazar 1ES 1553+113. In order to extract the Galactic halo component from the diffuse soft X-ray emission spectrum, accurately modeling the foreground components is crucial. Here we present complex modeling of the foregrounds with unprecedented details. A careful analysis of the spectrum yields two-temperature components of the halo gas ( T 1 em = 10 6.25 − 6.42 K, T 2 em = 10 6.68 − 6.92 K). We find that these temperatures obtained from the emission spectrum are not consistent with those from the absorption spectrum ( T 1 ab = 10 6.07 − 6.13 K, T 2 ab = 10 6.96 − 7.15 K), unlike the previous studies that found only one-temperature component of the Milky Way circumgalactic medium. This provides us with interesting insights into the nature of emitting and absorbing systems. We discuss several possibilities objectively, and conclude that most likely we are observing multiple (3–4) discrete temperatures between 10 5.5 K and ≥ 10 7 K in the Milky Way circumgalactic medium.

Semitransparent Sb2S3 thin film solar cells by ultrasonic spray pyrolysis for use in solar windows.

The integration of photovoltaic (PV) solar energy in zero-energy buildings requires durable and efficient solar windows composed of lightweight and semitransparent thin film solar cells. Inorganic materials with a high optical absorption coefficient, such as Sb2S3 (>105 cm−1 at 450 nm), offer semitransparency, appreciable efficiency, and long-term durability at low cost. Oxide-free throughout the Sb2S3 layer thickness, as confirmed by combined studies of energy dispersive X-ray spectroscopy and synchrotron soft X-ray emission spectroscopy, semitransparent Sb2S3 thin films can be rapidly grown in air by the area-scalable ultrasonic spray pyrolysis method. Integrated into a ITO/TiO2/Sb2S3/P3HT/Au solar cell, a power conversion efficiency (PCE) of 5.5% at air mass 1.5 global (AM1.5G) is achieved, which is a record among spray-deposited Sb2S3 solar cells. An average visible transparency (AVT) of 26% of the back-contact-less ITO/TiO2/Sb2S3 solar cell stack in the wavelength range of 380–740 nm is attained by tuning the Sb2S3 absorber thickness to 100 nm. In scale-up from mm2 to cm2 areas, the Sb2S3 hybrid solar cells show a decrease in efficiency of only 3.2% for an 88 mm2 Sb2S3 solar cell, which retains 70% relative efficiency after one year of non-encapsulated storage. A cell with a PCE of 3.9% at 1 sun shows a PCE of 7.4% at 0.1 sun, attesting to the applicability of these solar cells for light harvesting under cloud cover.

Electron temperature optimization for efficient water-window soft x-ray emission from discharge-produced highly charged zirconium ions

We determined the optimum electron temperature for water-window soft x-ray emission by observing the spectral behavior in the 2.3–4.4 nm region of highly charged zirconium (Zr) ions in hot hydrogen plasmas produced in a magnetically confined fusion device. In the water-window soft x-ray spectral region, the main emission involved resonant ${3}d - {4}f$3d−4f ($\Delta n = {1}$Δn=1) transitions. According to the collisional-radiative (CR) model verified by the experimental results, the ionic population for the charge states from ${{\rm Zr}^{14 + }}$Zr14+ to ${{\rm Zr}^{20 + }}$Zr20+ required to produce the emission was maximized in the electron temperature range of 80–180 eV. For laboratory-scale water-window soft x-ray source application, it is therefore important to produce an electron temperature significantly lower than 200 eV for the production of the suitable ionic charge states of ${{\rm Zr}^{14 + }} - {{\rm Zr}^{20 + }}$Zr14+−Zr20+.

Electrolyte Stability and Discharge Products of an Ionic-Liquid-Based Li–O2 Battery Revealed by Soft X-Ray Emission Spectroscopy

We investigate the electrolyte stability and discharge products of an ionic-liquid-based Li–O2 battery through soft X-ray emission spectroscopy (XES) experiments, which offer unique site specificit...

Redistribution of carbon caused by butterfly defects in bearing steels

Butterfly defects initiate from inclusions in the subsurface of steel bearing components subject to rolling contact. The white etching matter (WEM) microstructure is a characteristic of butterflies and is related to the dissolution of carbides and thus generally believed to be enriched with carbon, in supersaturated solid solution, relative to the parent microstructure. Here, several butterflies are investigated using wavelength dispersive spectroscopy (WDS), soft x-ray emission spectroscopy (SXES) and electron microscopy (EM). Contrary to established thinking, in all cases investigated the butterfly-neighbouring WEM was found to be depleted in carbon, relative to parent material, by around 27% (measured in counts). Furthermore, the carbon level was shown to be lower than the matrix itself, suggesting that solute carbon is also expelled from the WEM during its formation, possibly due to the low level of solubility of carbon in ferrite. This was observed in both AISI 52100 and 18NiCrMo14-6 bearing steels. In spite of this depletion, nano-indentation found that WEM in both alloys was ~17% harder than the parent material. This may explain the strings of micro-voids observed near the WEM-parent interface, which appear to play a role in the growth of the butterfly cracks. It is suggested that the increased hardness of the WEM is mainly due to microstructural changes, rather than changes in solute carbon concentration.

PM-06 Electronic Structure of Nitrogen-Doped Graphite Films Studied by Soft X-ray Emission Spectroscopy

PM-06 Electronic Structure of Nitrogen-Doped Graphite Films Studied by Soft X-ray Emission Spectroscopy

PM-05 Anisotropic Electronic Structure of Metal Borides Studied by Soft X-ray Emission Spectroscopy

PM-05 Anisotropic Electronic Structure of Metal Borides Studied by Soft X-ray Emission Spectroscopy

Soft X-ray spectral analysis of laser produced molybdenum plasmas using the fundamental and second harmonics of a Nd:YAG laser.

Our measurement of the soft X-ray emission of Mo plasmas produced by picosecond Nd:YAG lasers emitting on the fundamental (1064 nm, 150 ps) and second (532 nm, 130 ps) harmonics is presented. The contrast in intensity between spectral peaks and the intensity outside them is lower for the second harmonic produced plasmas probably due to the presence more intense satellite emission and higher optical thickness. The measured spectra are absolutely calibrated and the observed output photon flux was (7 - 9) × 1013 photons/sr in the water-window (2.3 - 4.4 nm) spectral range for a laser energy of 160 mJ independent of laser wavelength. However, in the short wavelength range 1.5 - 2 nm, the emission using the second harmonic is strongly enhanced and is even higher than for the maximum energy of 220 mJ of the fundamental wavelength, so despite inevitable energy losses, laser wavelength conversion may lead to emission enhancement in certain spectral ranges. This enhancement is attributed to higher absorption of short wavelength laser light and higher charge state generation in denser plasmas.

Suzaku observation of diffuse X-ray emission from a southwest region of the Carina Nebula

Abstract A southwest region of the Carina Nebula was observed with the Suzaku observatory for $47\:$ks in 2010 December. This region shows distinctively soft X-ray emission in the Chandra campaign observations. Suzaku clearly detects the diffuse emission above known foreground and background components between 0.4–$5\:$keV at the surface brightness of $3.3\times 10^{-14}\:$erg$\:$s$^{-1}\:$arcmin$^{-2}$. The spectrum requires two plasma emission components with $kT \sim 0.2$ and $0.5\:$keV, which suffer interstellar absorption of $N_{\,\rm H} \sim 1.9 \times 10^{21}\:$cm$^{-2}$. Multiple absorption models assuming two-temperature plasmas at ionization equilibrium or non-equilibrium are tested but there is no significant difference in terms of $\chi ^{2}/$d.o.f. These plasma temperatures are similar to those of the central and eastern parts of the Carina Nebula measured in earlier Suzaku observations, but the surface brightness of the hot component is significantly lower than those of the other regions. This means that these two plasma components are physically separated and have different origins. The elemental abundances of O, Ne, and Mg with respect to Fe favor that the diffuse plasma originates from core-collapsed supernovae or massive stellar winds.

Chandra Survey of Nearby Highly Inclined Disk Galaxies. V. Emission Structure and Origin of Galactic Coronae

Abstract The origin of the extended soft X-ray emission around nearby highly inclined disk galaxies (often called the X-ray corona) remains uncertain. The emission could arise from volume-filling hot gas and/or its interaction with cool gas. Morphological properties of the X-ray emission can provide additional information to distinguish these different origins. We define model-independent parameters H 50, H 75, and H 95—vertical scales that enclose 50%, 75%, and 95% of the total flux of the emission, respectively. We study the correlation of these parameters with galaxy properties inferred from infrared observations of a sample of nearby highly inclined disk galaxies with high-quality Chandra data. We find weak negative correlations between H 50 or H 75 and the surface star formation rate (I SFR), and no correlation for H 95. However, we detect strong negative correlations of the vertical concentration of the emission, defined as H 50/H 95 or H 75/H 95, with I SFR. Our findings suggest that the X-ray emission around disk galaxies is likely comprised of two components: the extended, weak emission, characterized by H 95, is influenced by the outflowing hot gas entrained in star formation driven winds, whereas the strong emission close to the disk, which is often rich in cool gas characterized by H 50 or H 75, is largely impacted by cool–hot gas interaction.