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Novel light sources have been new probes or “eyes” to develop our science and technology. Soft X-ray free-electron lasers (SXFELs) are an ultrahigh brilliant soft X-ray source with ultrashort pulse...

The shape of soft X-ray spectra and energy confinement dynamics is studied in experiments on central ECR heating with a power to 1 MW using the L-2M stellarator. It is shown that the spectra remain two-temperature with increasing heating power. In this case, the average electron energy in the epithermal spectral region increases reaching 25% of the average energy over the entire spectrum at an ECR heating power of 950 kW. It is shown that the plasma confinement energy in the L-2M stellarator gradually decreases at heating powers above 700 kW, which is associated with an increase in the plasma radiative loss power, caused by impurity accumulation.

Soft X-ray spectra coming from the ECR heating region, non-distorted by the effect of the plasma-wall interaction, are measured at the L-2M stellarator in experiments on axial and off-axial ECR heating. In both cases, the measured soft X-ray spectra turned out to be non-Maxwellian. It was found that the electrons forming the suprathermal spectral region are produced in the heating region, but do not come from the plasma-wall interaction region.

We present our $AstroSat$ soft X-ray observations of a compact binary system, AR Sco, and analysis of its X-ray observations with $Chandra$ that were taken only about a week before the $AstroSat$ observations. An analysis of the soft X-ray ($0.3-2.0$ keV) data limits the modulation of the spin, orbital, or beat periods to less than 0.03 counts s$^{-1}$ or $, Comment: 9 pages, 8 figures, to be published in the Journal of Astrophysics and Astronomy

Laboratory and synchrotron X-ray tomography are powerful tools for non-invasive studies of biological samples at micrometric resolution. In particular, the development of phase contrast imaging is enabling the visualization of sample details with a small range of attenuation coefficients, thus allowing in-depth analyses of anatomical and histological structures. Reproductive medicine is starting to profit from these techniques, mainly applied to animal models. This study reports the first imaging of human ovarian tissue where the samples consisted of surgically obtained millimetre fragments, properly fixed, stained with osmium tetroxide and included in epoxydic resin. Samples were imaged by the use of propagation phase contrast synchrotron radiation micro-computed tomography (microCT), obtained at the SYRMEP beamline of Elettra light source (Trieste, Italy), and X-ray absorption microCT at the Theoretical Biology MicroCT Imaging Laboratory in Vienna, Austria. The reconstructed microCT images were compared with the soft X-ray absorption and phase contrast images acquired at the TwinMic beamline of Elettra in order to help with the identification of structures. The resulting images allow the regions of the cortex and medulla of the ovary to be distinguished, identifying early-stage follicles and visualizing the distribution of blood vessels. The study opens to further application of micro-resolved 3D imaging to improve the understanding of human ovary's structure and support diagnostics as well as advances in reproductive technologies.

Arrival timing diagnostics between a soft X-ray free-electron laser and synchronized optical laser pulses were performed at SACLA BL1., An arrival timing monitor for the soft X-ray free-electron laser (XFEL) beamline of SACLA BL1 has been developed. A small portion of the soft XFEL pulse is branched using the wavefront-splitting method. The branched FEL pulse is one-dimensionally focused onto a GaAs wafer to induce a transient reflectivity change. The beam branching method enables the simultaneous operation of the arrival timing diagnostics and experiments. The temporal resolution evaluated from the imaging system is ∼22 fs in full width at half-maximum, which is sufficient considering the temporal durations of the soft XFEL and the optical laser pulses.

We demonstrate the feasibility of soft X-ray absorption spectroscopy in the water window using a table-top laser-based approach with organic molecules and inorganic salts in aqueous solution. A high-order harmonic source delivers femtosecond pulses of short wavelength radiation in the photon energy range from 220 to 450 eV. We report static soft X-ray absorption measurements in transmission on the solvated compounds O=C(NH

The Soft X-ray Telescope (SXT) aboard the $AstroSat$ satellite is the first Indian X-ray telescope in space. It is a modest size X-ray telescope with a charge coupled device (CCD) camera in the focal plane, which provides X-ray images in the $\sim 0.3-8.0$ keV band. A forte of SXT is in providing undistorted spectra of relatively bright X-ray sources, in which it excels some current large CCD-based X-ray telescopes. Here, we highlight some of the published spectral and timing results obtained using the SXT data to demonstrate the capabilities and overall performance of this telescope., 8 pages, 6 figures, accepted for publication in The Journal of Astrophysics and Astronomy

With the ongoing upgrades FLASH2020+ will extend capabilities of existing Free- Electron-Lasers. Combining a superconducting electron-beam accelerator with a new external seeding scheme, FLASH2020+ will provide up to 1 MHz repletion rate highly coherent pulses.

This paper presents a statistical analysis of soft X-ray flares during the period January 1986 to June 2017 covering the last three solar cycles (SCs) 22, 23, and 24. We have analyzed the distribution of flare number, the relationship between the occurrence rate of soft X-ray flares and solar activity, and the duration of different intensity class (B, C, M, and X) solar flares during the period of investigation. The total occurrence rates of M and X class flares are 10.33%, 6.77%, and 5.45% in SCs 22, 23, and 24, respectively, which indicates that SC 22 is an SC with frequent large flares. Meanwhile, the M and X class flares are mainly concentrated in solar maximum (71.13%) in SC 22. The correlation coefficients between the annual number of flares and solar F10.7 index, X-ray flux in 0.1–0.8 nm, and EUV flux in 0.1–50 nm in SC 24 (0.91, 0.88, and 0.96) are greater than that in SCs 23 (0.87, 0.85, and 0.86) and 22 (0.88 and 0.81). The median values of the duration of M and X class flares are 39.00 and 71.50 minutes in SC 22, 21.00 and 26.50 minutes in SC 23, and 19.00 and 24.00 minutes in SC 24. The duration of M and X class flares in SC 22 is obviously longer than that in SCs 23 and 24. In addition, the duration of flares increases with the increase of flare intensity.

We develop an Arrival Time Monitor (ATM) achieving high sensitivity for soft X-ray pulses in low-fluence conditions. The ATM cross-correlates ultrashort X-ray with 800nm laser pulses using a new multi-layer target designed and grown in-house to achieve optimal sensitivity.

Progress in nanotechnology calls for material probing techniques of high sensitivity and resolution. Such techniques are also used for high-impact studies of nanoscale materials in medicine and biology. Soft X-ray microscopy has been successfully used for investigating complex biological processes occurring at micrometric and sub-micrometric length scales and is one of the most powerful tools in medicine and the life sciences. Here, we present the capabilities of the TwinMic soft X-ray microscopy end-station at the Elettra synchrotron in the context of medical and biological imaging, while we also describe novel uses and developments.

The Soft X-ray Imager (SXI) on-board the joint ESA-CAS SMILE mission is a wide-field lobster-eye telescope designed to characterize the Earth's magnetospheric boundaries, by observing emission from the solar wind charge exchange (SWCX) process in the soft X-ray band. It has two large CCD370 (Teledyne-e2v) detectors, derived from the CCD-Bruyeres for ESA’s PLATO mission, with minor optimizations for soft X-ray detection, related to higher responsivity and increased radiation hardness. We present the first performance results under X-ray illumination of the CCD370 in SXI-specific operating conditions, including 6x6 on-chip pixel binning, over a range of pixel readout rates and operating temperatures.

We present observations of four bright stars observed with the AstroSat Soft X-ray Telescope (SXT). Visible light from bright stars like these can leak through the very thin filter in front of the CCD in the focal plane CCD camera of the SXT and thus making the extraction of X-ray events difficult. Here, we show how to extract the X-ray events without contamination by the visible light. The procedure applied to four bright stars here demonstrates how reliable X-ray information can be derived in such cases. The sample of bright stars studied here consists of two A spectral types (HIP 19265, HIP 88580), one G/K Giant (Capella), and a nearby M-type dwarf (HIP 23309). No X-ray emission is observed from the A-type stars, as expected. X-ray spectra of Capella and HIP 23309 are derived and modeled here, and compared with the previous X-ray observations of these stars to show the reliability of the method used. We find that optical light can start to leak in the very soft energy bands below 0.5 keV for stars with V=8 mag. In the process, we present the first X-ray spectrum of HIP 23309., To appear in the Journal of Astrophysics and Astronomy; 8 pages, 7 figures

A novel ultrahigh-resolution x-ray microscope achieves 8-nm spatial resolution and accurately maps chemistry in nanomaterials., The analysis of chemical states and morphology in nanomaterials is central to many areas of science. We address this need with an ultrahigh-resolution scanning transmission soft x-ray microscope. Our instrument provides multiple analysis tools in a compact assembly and can achieve few-nanometer spatial resolution and high chemical sensitivity via x-ray ptychography and conventional scanning microscopy. A novel scanning mechanism, coupled to advanced x-ray detectors, a high-brightness x-ray source, and high-performance computing for analysis provide a revolutionary step forward in terms of imaging speed and resolution. We present x-ray microscopy with 8-nm full-period spatial resolution and use this capability in conjunction with operando sample environments and cryogenic imaging, which are now routinely available. Our multimodal approach will find wide use across many fields of science and facilitate correlative analysis of materials with other types of probes.

New free electron lasers, such as SLAC's LCLS-II, will provide unique scientific imaging opportunities with soft xrays from 250eV-1.5KeV. In order to fully utilize these facilities, we need to develop detectors with both shallow entrance windows and adequate signal-to noise ratios to utilize the soft x-rays effectively. Low Gain Avalanche Detectors (LGADs) have the potential for improved signal-to-noise ratio due to the built-in amplification. However, the conventional LGAD structure is not conducive to a shallow entrance window. In this work, we propose a new LGAD device structure that can incorporate a shallow entrance window utilizing microwave annealing to activate the dopant in the entrance window. Process and device simulations are used to demonstrate the feasibility and performance of the proposed structure.

We evaluated laser-induced damage thresholds (LIDTs) on silica glasses by two kinds of ultra-short soft X-ray laser pulses (13.5 nm, 70 fs, and 13.9 nm, 7 ps). The comparison of our experimental results and the reported values observed by nanosecond soft X-ray pulse revealed a pulse width dependence of LIDTs on silica glasses in the soft X-ray region. The relationship between the pulse width and LIDTs provided valuable discussions of the laser-induced damage mechanism.

High-end precision optics are generally manufactured through traditional processes, which produce unique shapes and smooth surfaces, and the modern figure correction process. Particularly for soft x-ray regions, the demand for accurate free-form optics with complex and steep shapes has been increasing recently. Wolter mirrors and ring-focusing mirrors are representative of these types of optics, which are expected to be the next-generation devices for soft x-ray microscopy. To fabricate these mirrors with sufficient accuracy to achieve ideal optical performances, both traditional and modern processes must be optimized ad hoc. In this study, we apply the high-precision lens fabrication process to a monolithic Wolter mirror and a ring-focusing mirror. The surface measurement results of the mirrors suggest that it is possible to fabricate single-nanometer accurate soft x-ray mirrors with steep shapes in complex geometries.

Femtosecond X-ray absorption spectroscopy (XAS) is a powerful method to investigate the dynamical behavior of a system after photoabsorption in real time. So far, the application of this technique has remained limited to large-scale facilities, such as femtosliced synchrotrons and free-electron lasers (FEL). In this work, we demonstrate femtosecond time-resolved soft-X-ray absorption spectroscopy of liquid samples by combining a sub-micrometer-thin flat liquid jet with a high-harmonic tabletop source covering the entire water-window range (284–538 eV). Our work represents the first extension of tabletop XAS to the oxygen edge of a chemical sample in the liquid phase. In the time domain, our measurements resolve the gradual appearance of absorption features below the carbon K-edge of ethanol and methanol during strong-field ionization and trace the valence-shell ionization dynamics of the liquid alcohols with a temporal resolution of ∼30 fs. This technique opens unique opportunities to study molecular dynamics of chemical systems in the liquid phase with elemental, orbital, and site sensitivity. ISSN:1948-7185

In this article, we will show recent hydrodynamic simulations of quasi-steady state (QSS) plasma-based amplifiers of soft X-rays. These simulations are being performed with the 2D radiative-hydrodynamics code ARWEN. Selected results among the simulations performed will be presented, showing the inadequacy of some materials compared to others (Molybdenum and Zinc) for QSS scheme, mainly due to energy loses via radiative transfer. The importance of radiative transfer will be further assessed. Finally, ongoing results on the optimization of Titanium QSS plasma-based soft X-ray laser will be presented.

In the Brewster angle geometry, a multilayer mirror reflects s-polarization component and suppresses the p-polarization componentfrom the incident beam. In the present study a Mo/Si multilayer of d=97A, N=20 layer pairsis used to analyze the polarization characteristics of SR beam of 130A wavelengthat theexperimental station of the reflectivity beamline of Indus-1 synchrotron source. The SR beam polarization characteristics are analyzed at various vertical height at the experimental station. The degree of linear polarization (DOLP) and degree of circular polarization (DOCP) have been evaluated for each vertical height. It is shown that the SR beam at the experimental station of the beamline has 83% DOLP and it gradually decreases with increasing vertical height, on the other hand DOCP increases from 54% to 98%.

In order to realize a compact and high repetition rate plasma X-ray laser, we have developed a recombination scheme plasma X-ray laser. In particular, we focused on a laser oscillation of Li-like aluminum 3d-4f transition (15.5 nm), which was already demonstrated in a high-density and low-temperature Al laser plasma with a low gain coefficient. In this study, by using an Nd:YAG laser (500 ps, 3 J, 16 pulse-trains) we created the lasing media and succeeded in laser oscillation at 15.5 nm. The optimization of the pulse-train in terms of the pulse duration and its interval enhanced the gain coefficient to g = 4.3 cm−1.

International audience; We exploit echo-enabled harmonic generation (EEHG) to produce fully coherent free-electron laser (FEL) pulses at soft-x-ray wavelengths and shape their spectrotemporal content. In an EEHG FEL, the longitudinal phase space of the relativistic electron beam that amplifies light is precisely tailored using two external seed lasers and two magnetic chicanes. We show that the spectrotemporal properties of the emitted radiation can be controlled by tuning the bandwidth, linear frequency chirp, and intensity of one of the seed lasers. The experimental data are supported by analytical and numerical models. Our results open a pathway toward coherent control of quantum processes at short wavelengths in the fields of applied physics, chemistry and biology, where manipulating the radiation spectrum is essential. The ability to precisely control the spectrotemporal content of intense, short-wavelength FEL pulses and the low sensitivity of the radiation to electron-beam imperfections make the technique an ideal candidate for use in chirped-pulse amplification schemes.

At MAX IV, a fourth-generation, or diffraction-limited, synchrotron light source, six soft X-ray monochromators (Bloch, Veritas, HIPPIE, SPECIES, FinEstBeAMS and SoftiMAX beamlines) are examined with a focus on their resolving power, energy range and the time required to change measurement range. When measuring the mechanical resolution defined by angular vibrations, FinEstBeAMS shows a resolving power R of better than 30000 for all studied c ff values, while, for HIPPIE, the resolving power for c ff = 2.25 and higher and for energies lower than 1 keV is better than 100000., MAX IV is a fourth-generation, or diffraction-limited, synchrotron light source with a number of state-of-the-art beamlines. The performance of a beamline is, to a high degree, set by the energy resolution it can achieve, which in turn is governed to a large extent by the monochromator. During the design phase of a monochromator, the mechanical requirements must be fully understood and met with margin. During commissioning, the performance must be verified and optimized. In this paper, six soft X-ray monochromators at MAX IV beamlines (Bloch, Veritas, HIPPIE, SPECIES, FinEstBeAMS and SoftiMAX) are examined with a focus on their resolving power, energy range and the time required to change measurement range, as those parameters are dependent on each other. The monochromators have a modern commercial design, planned and developed in close collaboration with the vendors. This paper aims to present the current status of the commissioning at MAX IV with emphasis on elucidating the mechanical limitations on the performance of the monochromators. It contains analysis of the outcome and our approach to achieve fast and high-resolution monochromators.

We have experimentally demonstrated circular polarization generation from linear polarized soft X-ray at synchrotron by adopting a thin magnetic film polarizer. Polarizer is composed of Co/Pt multilayer with a perpendicular magnetic anisotropy, which allows us to easily accommodate without needing any tilting angle into the measurement setup since the circular polarization is generated for the X-ray with normal incidence and transmission. Generated circular polarization is examined by observing magnetic domain features based on the X-ray magnetic circular dichroism, where ∼11% of circular component is estimated compared to the case of full circular polarization.

Arrival timing diagnostics performed at a soft X-ray free-electron laser (FEL) beamline of SACLA are described. Intense soft X-ray FEL pulses with one-dimensional focusing efficiently induce transient changes of optical reflectivity on the surface of GaAs. The arrival timing between soft X-ray FEL and optical laser pulses was successfully measured as a spatial position of the reflectivity change. The temporal resolution evaluated from the imaging system reaches ∼10 fs. This method requires only a small portion of the incident pulse energy, which enables the simultaneous operation of the arrival timing diagnostics and experiments by introducing a wavefront-splitting scheme.

Elemental and chemical state maps of p/n-controlled SrB6 bulk specimens are presented by using a soft X-ray emission spectroscopy electron microscope. Those bulk specimens were obtained by sintering powder specimens, prepared by the molten-salt method with different compositions of initial materials. A Sr-map, a chemical shift map of B K-emission, and the spectra of characteristic regions of those materials were compared. It was observed that a local Sr deficiency caused a local hole-doped region, confirmed by a chemical shift in the B K-emission spectrum. n-type SrB6 was rather homogeneous. On the other hand, the p-type SrB6 bulk specimen was a mixture of two different p-type regions. This mixed nature originated, presumably, from an uneven Sr content of SrB6 particles prepared by the molten-salt method using a Sr-deficient starting material. A separation process of the two types of materials will realize a high-quality homogeneous p-type SrB6 bulk specimens.

The Shanghai Soft X-ray Free-Electron Laser facility (SXFEL) is a single-pass FEL facility designed to cover the photon spectrum from 10 nm to 2nm based on self-amplified spontaneous emission (SASE...

The time history of the temperature and the emission measure of the solar flare plasma have been studied relying upon the experimental data on the soft X-rays recorded by the IRIS spectrometer on June 29, 2002 (F1) and March 27, 2003 (F2). F1 was a thermal flare and was not accompanied by hard X-rays. This data analysis revealed that at least two sequential energy-release processes occurred during the F1 event. The F2 event took place behind the limb, so only the top part of the flare loop being the soft X-ray source was recorded by the satellite-based spectrometer. From this data analysis it appeared that fast plasma heating occurred in the initial stage of F2 and then the flare region expanded and the emission measure of flare plasma increased.

In-situ/operando techniques have been developed for spectromicroscopic studies of heavy elements using hard X-rays with high transmittance in samples and long focal length of optical elements (i.e....

BaF 2 was ablated by a capillary-discharge pumped soft X-ray laser at 46.9 nm focused by a toroidal mirror at a grazing incidence of 83°. The damaged area, induced by both single and multiple laser pulses, was determined to be covered with fringe-like nanostructures with spacings of approximately 400 nm and mastoid nanostructures with diameters of approximately 600 nm. In this study, we analyze the morphology of the detected damage patterns and discuss the damage mechanism. Results indicate that the depth of the nanostructures varies with different pulse numbers and laser power densities.

This paper presents the designs and simulations of twin Wolter mirrors for focusing and imaging experiments with soft Xray free electron lasers. Wave-optical simulations at a photon energy of 100 eV indicate that the designed focusing Wolter mirror focuses soft X-ray beams to a 300 nm × 200 nm spot with an acceptable rotational error of 1.7 mrad × 1.4 mrad and that the objective Wolter mirror, which receives the beam that passes through the focusing Wolter mirror and a sample, forms bright-field images with a spatial resolution of 140 nm × 140 nm. The focusing Wolter mirror enables long-term experiments with high stability, and the objective Wolter mirror is applicable to imaging-before-destruction.

New instruments and methods for nanoimaging with the use of a compact laser plasma soft X-ray source are presented. The source is based on a double-stream gas puff target irradiated with nanosecond laser pulses from a Nd:YAG laser. Three imaging instruments, operating in the soft X-ray ‘water window’ range, namely two soft X-ray transmission microscopes and a soft X-ray contact microscope, have been developed. The transmission microscopes are based on grazing incidence Wolter type or diffractive Fresnel type optics. Application of these instruments for nanoimaging of hydrated and dry biological samples is presented. A new method for X-ray nanoimaging based on optical coherence tomography (OCT) technique using broad-band soft X-ray emission from the laser plasma source is also demonstrated.

To advance the frontiers of ultrafast X-ray science, Shanghai soft X-ray free-electron laser (SXFEL) user facility was proposed to develop which is now under construction as planned. The SXFEL facility provides ultraintense femtosecond X-ray pulses from 0.1 keV to 1 keV in a repetition rate of 50 Hz. The first phase of the SXFEL includes two beamlines and 5 experimental end-stations. The SXFEL user facility provides some advanced X-ray measurement tools in the research fields of biomaterial, condensed matters, atomic and molecular physics, and novel functional materials by means such as coherent diffraction imaging, time-resolved resonant X-ray scattering, and single-pulse time-resolved x-ray emission spectroscopy etc. In this presentation, I will report the latest status of the beamlines at Shanghai SXFEL.

International audience; This work presents an innovative usage of the GEMpix detector for soft X-rays (SXR) measurements aimed to make an estimate of the electron temperature of a Laser Produced Plasma (LPP). The GEMpix is a proportional gas detector based on three Gas Electron Multipliers (GEMs) with a Front-End Electronics (FEE) based on four Timepix chips. This FEE provides the Time over Threshold (ToT) acquisition mode pixel by pixel and then a digital measure of the released charge in the gas mixture. In addition, the charge can be amplified through the GEM foils with 4 orders of magnitude spanning gain offering, in this way, a big dynamic range and adjustable sensitivity. Chip design provides a threshold for each channel. All the thresholds are set in order to cut electronic noise and detect X-rays. In this configuration, a cut on the low amplitude signals is set, but the gain has been tuned in order to observe the main signal due to the soft X-rays reaching the detector. This detector works in an energy range between 2 to 15 keV . It offers good imaging properties, high efficiency and absolute calibration. It offers a good immunity to Electromagnetic Pulse (EMP), as checked at VEGA-2 laser facility (hundreds of TW in about 30 fs). In these experiments, where the formation of warm dense matter produced by blast waves has been studied, a measure of the plasma temperature was required. This measurement was realized applying some filters on the active area of the detector, in correspondence of three chips. With this configuration a study of the GEMpix response due to the photons coming from the coronal plasma produced by the laser on the target has been done for each single shot. GEMpix revealed innovative and attractive features, compared to the state of the art where passive films or detectors based on indirect conversion are used, for SXR imaging and spectral analysis to infer the electron temperature.

High harmonic generation (HHG) of an intense laser pulse is a highly nonlinear optical phenomenon that provides the only proven source of tabletop attosecond pulses, and it is the key technology in attosecond science. Recent developments in high-intensity infrared lasers have extended HHG beyond its traditional domain of the XUV spectral range (10–150 eV) into the soft X-ray regime (150 eV to 3 keV), allowing the compactness, stability and sub-femtosecond duration of HHG to be combined with the atomic site specificity and electronic/structural sensitivity of X-ray spectroscopy. HHG in the soft X-ray spectral region has significant differences from HHG in the XUV, which necessitate new approaches to generating and characterizing attosecond pulses. Here, we examine the challenges and opportunities of soft X-ray HHG, and we use simulations to examine the optimal generating conditions for the development of high-flux, attosecond-duration pulses in the soft X-ray spectral range. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.

In this paper, we are presenting the Percival detector, a monolithic CMOS Imager for detection of soft x-rays in Synchrotron Rings and Free Electron Lasers. The imager consists in a 2D array of many (2M) small (27um pitch) pixels, without dead or blind zones in the imaging area. The imager achieves low noise and high dynamic range by means of an adaptive-gain in-pixel circuitry, that has been validated on prototypes. The imager features on-chip Analogue-to-Digital conversion to 12+1 bits, and has a readout speed which is compatible with most of Free Electron Laser Facilities. For direct detection of low-energy x-rays, the imager is back-illuminated and post-processed to achieve 100% fill factor.

We report the direct wavefront characterization of an intense ultrafast high-harmonic-seeded soft X-ray laser (λ=32.8 nm) depending on the arrival time of the seed pulses by high-resolution ptychographic imaging and subsequently perform single-shot nanoscale imaging.

The discovery of two-dimensional (2D) materials with single or a few-atom-thick layers has presented unprecedented opportunities to study, control and harness the properties of van der Waals (vdW) materials at their 2D limit. It also offers a platform that allows the arbitrary creation of heterostructures in a materials-by-design approach with properties tailored by the constituting components. Combining organic molecules with 2D materials to form hybrid heterointerfaces has recently emerged as a facile and versatile approach to engineer the electronic, optical, magnetic and chemical properties of 2D materials for new or optimized device applications. Underpinning the development of organic–2D materials heterostructures is the ability to interrogate the interfacial electronic structures and properties at multiple dimensions. This review provides a timely update on the application of synchrotron-based soft X-ray spectroscopies (SR-SXS) in the characterization of organic–2D materials interfaces. By harnessing the unparalleled high energy resolution, tunable energy, high brilliance and tunable polarization inherent to synchrotron radiation, electronic structures, charge transfer dynamics, molecular orientations and spin configurations at the hybrid interfaces can be examined, which helps us to formularize a coherent understanding of the organic–2D materials interfaces that will guide the design of new hybrid vdW structures and devices. We also offer our perspective on the future application of SR-SXS in the exploration of organic–2D materials heterostructures.

A forward modeling technique is developed for determining the characteristic features of observed MHD modes from the line-of-sight data of the soft x-ray (SXR) tomography diagnostics in the Wendelstein 7-X (W7-X) stellarator. In particular, forward modeling is used to evaluate the poloidal mode numbers m, radial location, poloidal rotation direction and ballooning character of the MHD modes. The poloidal mode structures have been modeled by the radially localized Gaussian-shaped emission regions rotating along the magnetic surfaces. In the present study the cases of rigid-shape emission regions and flexible emission regions are modeled. Various mode phase velocity dependences on the magnetic surface position are simulated. The modeled phase dynamics of line-integrated oscillations and the distribution of oscillation amplitudes are compared with the experimental signals of the SXR cameras which observe the plasma at various viewing angles in the poloidal cross-section. Application of this technique enables describing of the 1–50 kHz modes. In particular, in the discharge W7X-PID 20180918.045 three identified branches with the poloidal mode numbers m= 8, m= 10 and m= 11 localized at ρ ≈ 0.3 are rotating in the clockwise poloidal direction. The present paper reports the first application of the forward modeling technique to the data from the SXR diagnostics in W7-X. The high m-modes are identified by forward modeling in W7-X.

Soft x-ray tomograms are inferred from experimental data obtained during the recent operational phases of the superconducting, optimized stellarator Wendelstein 7-X. It is shown that the reconstructed soft x-ray emission profiles of the plasma are consistent with the numerically calculated magneto-hydrodynamic equilibrium of Wendelstein 7-X. In order to obtain reliable tomograms, the full chain of electrical and geometrical influences on the x-ray observation has to be taken into account. This has been achieved by formulation and application of an extended forward model. The forward model has been verified using phantom data derived from surrogate tomograms.