X-ray Wavelength Range Research Articles

Can Emission Measure Distributions Derived from Extreme-ultraviolet Images Accurately Constrain High-temperature Plasma?

Measuring the relative amount of high-temperature, low emission measure (EM) plasma is considered to be a smoking-gun observation to constrain the frequency of plasma heating in coronal structures. Often, narrowband, extreme-ultraviolet images, such as those obtained by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO), are used to determine the EM distribution, though the sensitivity to high-temperature plasma is limited. Conversely, the soft X-ray wavelength range offers multiple high-temperature diagnostics, including emission lines of N vii, O vii, O viii, Fe xvii, Ne ix, and Mg xi, which can provide tight constraints to the high-temperature plasma in the log T = 6.1–6.7 (∼1–5+ MK) range. The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS), a slitless spectrograph launched on a NASA sounding rocket on 2021 July 30, resolved an X-ray-bright point in multiple emission lines in the soft X-ray wavelength range. Using coordinated observations of the same X-ray-bright point from SDO/AIA, we compare and contrast the EM distributions from the EUV image data, the X-ray spectra, and the combined EUV and X-ray data set. In this paper, we demonstrate that EM distributions from SDO/AIA data alone can overestimate the amount of high-temperature (log T > 6.4) plasma in the solar corona by a factor of 3–15. Furthermore, we present our effort to cross-calibrate Hinode/X-ray Telescope (XRT) response functions by comparing the observed XRT fluxes with the predicted ones from combined MaGIXS-1 + AIA EM analysis.

О численном моделировании трековых мембран, используемых в качестве коллиматоров рентгеновского излучения

In this work, we present the results of numerical modeling of distribution of the field amplitude inside micron-sized through cylindrical pores in polymer track membranes in the soft X-ray wavelength range 13.5–30.4 nm. The calculations were performed by numerically solving the 3D parabolic equation with a finite-difference method using an exact transparent boundary condition. The dependences of the X-ray transmittivity through a pore on the incidence angle as well as on the pore diameter were computed. For the membranes with some thicknesses and pore diameters, calculated angular dependences of the transmittance are compared with the measurements known from the literature. It is demonstrated that the calculations agree with the measurements if a transition layer on the inner surface of the pores, which accounts for the finite surface roughness, is introduced.

Large-scale Multiconfiguration Dirac–Hartree–Fock Calculations for Astrophysics: C-like Ions from O iii to Mg vii

Large-scale multiconfiguration Dirac–Hartree–Fock calculations are provided for the n ≤ 5 states in C-like ions from O iii to Mg vii. Electron correlation effects are accounted for by using large configuration state function expansions, built from sets of orbitals with principal quantum numbers n ≤ 10. An accurate and complete data set of excitation energies, wavelengths, radiative transition parameters, and lifetimes is offered for the 156 (196, 215, 272, 318) lowest states of the 2s 22p 2, 2s2p 3, 2p 4, 2s 22p3s, 2s 22p3p, 2s 22p3d, 2s2p 23s, 2s2p 23p, 2s2p 23d, 2p 33s, 2p 33p, 2p 33d, 2s 22p4s, 2s 22p4p, 2s 22p4d, 2s 22p4f, 2s2p 24s, 2s2p 24p, 2s2p 24d, 2s2p 24f, 2s 22p5s, 2s 22p5p, 2s 22p5d, 2s 22p5f, and 2s 22p5g configurations in O iii (F iv, Ne v, Na vi, Mg vii). By comparing available experimental wavelengths with the MCDHF results, the previous line identifications for the n = 5, 4, 3 → n = 2 transitions of Na vi in the X-ray and EUV wavelength range are revised. For several previous identifications discrepancies are found, and tentative new (or revised) identifications are proposed. A consistent atomic data set including both energy and transition data with spectroscopic accuracy is provided for the lowest hundreds of states for C-like ions from O iii to Mg vii.

A new technology of thermoplastic glass bending for the manufacture of cylindrical surfaces of hard X-ray range mirrors

The paper presents a new technique for thermoplastic bending of glass. The technique makes it possible to produce cylindrical surfaces with a guide in the form of a parabola, ellipse, etc. for mirrors in the hard X-ray wavelength range (λ~0.1 nm). Three samples of the surface of an elliptical cylinder were prepared using this technique. The production time for each sample was two days. The deviation of the guide and its local angle from the calculated values for all samples does not exceed Delta y=0.5 μm and Deltaα=7·10-5 rad, respectively. It is shown that when such surfaces are etched for two hours, their accuracy can be improved by more than two orders of magnitude (Delta y=2 nm, Deltaα=5·10-7 rad). Keywords: focusing X-ray mirrors, cylindrical mirrors, multilayer structures

Новая методика термопластического изгиба стекла для изготовления цилиндрических поверхностей зеркал жесткого рентгеновского диапазона

The paper presents a new technique for thermoplastic bending of glass. The technique makes it possible to produce cylindrical surfaces with a guide in the form of a parabola, ellipse, etc. for mirrors in the hard X-ray wavelength range (λ~0.1 nm). Three samples of the surface of an elliptical cylinder were prepared using this technique. The production time for each sample was two days. The deviation of the guide and its local angle from the calculated values for all samples does not exceed Δy = 0.5 µm and Δα = 7*10-5 rad, respectively. It is shown that when such surfaces are etched for two hours, their accuracy can be improved by more than two orders of magnitude (Δy = 5 nm, Δα = 5*10-7 rad).

Design study of APS-U-type hybrid-MBA lattice for mid-energy DLSR

In recent years, a new generation of storage ring-based light sources, known as diffraction-limited storage rings (DLSRs), whose emittance approaches the diffraction limit for the range of X-ray wavelengths of interest to the scientific community, has garnered significant attention worldwide. Researchers have begun to design and build DLSRs. Among various DLSR proposals, the hybrid multibend achromat (H-MBA) lattice enables sextupole strengths to be maintained at a reasonable level when minimizing the emittance; hence, it has been adopted in many DLSR designs. Based on the H-7BA lattice, the design of the Advanced Photon Source Upgrade Project (APS-U) can effectively reduce emittance by replacing six quadrupoles with anti-bends. Herein, we discuss the feasibility of designing an APS-U-type H-MBA lattice for the Southern Advanced Photon Source, a mid-energy DLSR light source with ultralow emittance that has been proposed to be built adjacent to the China Spallation Neutron Source. Both linear and nonlinear dynamics are optimized to obtain a detailed design of this type of lattice. The emittance is minimized, while a sufficiently large dynamic aperture (DA) and momentum acceptance (MA) are maintained. A design comprising 36 APS-U type H-7BAs, with an energy of 3 GeV and a circumference of 972 m, is achieved. The horizontal natural emittance is 20 pm·rad, with a horizontal DA of 5.8 mm, a vertical DA of 4.5 mm, and an MA of 4%, as well as a long longitudinal damping time of 120 ms. Subsequently, a few modifications are performed based on the APS-U-type lattice to reduce the maximum value of damping time from 120 to 44 ms while maintaining other performance parameters at the same level.

Harmonics Generation in Experiments with Free-Electron Lasers in the X-Ray Wavelength Range: a Theoretical Analysis

The generation of undulator X-ray radiation harmonics in free-electron lasers (FELs), which has been observed in different experiments, has been given an analytical explanation. Expressions for spectrum lines and radiation intensity are written in explicit form in terms of generalized Bessel and Airy functions with regard to the spreads of electron energy, electron beam size, emittance, spectrum line splitting, and magnetic field constant components. The theory proposed here adequately explains the spectrum and intensity of radiation harmonics in all experiments with a SACLA FEL, a Linac coherent light source (LCLS) based on an FEL, PAL-XFEL, SwissFEL, and other equipment conducted under different conditions in a wide wavelength range, including hard X-ray radiation.

Modification and Polishing of the Holographic Diffraction Grating Grooves by a Neutralized Ar Ion Beam

We describe the method for increasing the efficiency of holographic diffraction gratings (HDGs) intended for operation in the X-ray wavelength range. We describe the procedure of processing of HDG surface for reducing the amplitude and roughness of grooves. For reducing the groove amplitude, we have used Xe ions with an energy of 600 eV, while ion polishing was performed with Ar ions having an energy of 800 eV. It is shown that, after ion polishing, the diffraction efficiency of the grating at a wavelength of 4.47 nm increases by almost four times.

The Talbot effect in X-ray range

This article describes the advances made using Talbot effect in X-ray wavelength range. The possibilities of phase-contrast interferometry using a three-grating Talbot interferometer are noted. The achievements of applying the Talbot effect in nanoscale X-ray lithography are discussed. The need to include this material in courses on X-ray optics, read in Russian Technical Universities, is underlined.

Spectral energy distribution of blazars

AbstractThis study focuses on spectral energy distributions and light-curves of blazars and radio galaxies, and the testing of the existing models with a view to appropriately predict a new model that will nearly accurately present the nature of the energy outflows of these super-massive bodies. Understanding blazar emission is very important as it relates more directly to the physics of the AGN’s central black hole. X-ray, radio and gamma-ray wavelength range data on blazars and radio galaxies from archived data has been collected and a detailed investigation of the spectral energy distribution patterns of the blazars and radio galaxies carried out so as to fit the data in the various models. The results of this investigation will be discussed in detail in this presentation.

NIST Standard Reference Material 3600: Absolute Intensity Calibration Standard for Small-Angle X-ray Scattering.

The certification of a new standard reference material for small-angle scattering [NIST Standard Reference Material (SRM) 3600: Absolute Intensity Calibration Standard for Small-Angle X-ray Scattering (SAXS)], based on glassy carbon, is presented. Creation of this SRM relies on the intrinsic primary calibration capabilities of the ultra-small-angle X-ray scattering technique. This article describes how the intensity calibration has been achieved and validated in the certified Q range, Q = 0.008-0.25 Å-1, together with the purpose, use and availability of the SRM. The intensity calibration afforded by this robust and stable SRM should be applicable universally to all SAXS instruments that employ a transmission measurement geometry, working with a wide range of X-ray energies or wavelengths. The validation of the SRM SAXS intensity calibration using small-angle neutron scattering (SANS) is discussed, together with the prospects for including SANS in a future renewal certification.

Refraction effects in soft x-ray multilayer blazed gratings.

A 2500 lines/mm Multilayer Blazed Grating (MBG) optimized for the soft x-ray wavelength range was fabricated and tested. The grating coated with a W/B4C multilayer demonstrated a record diffraction efficiency in the 2nd blazed diffraction order in the energy range from 500 to 1200 eV. Detailed investigation of the diffraction properties of the grating demonstrated that the diffraction efficiency of high groove density MBGs is not limited by the normal shadowing effects that limits grazing incidence x-ray grating performance. Refraction effects inherent in asymmetrical Bragg diffraction were experimentally confirmed for MBGs. The refraction affects the blazing properties of the MBGs and results in a shift of the resonance wavelength of the gratings and broadening or narrowing of the grating bandwidth depending on diffraction geometry. The true blaze angle of the MBGs is defined by both the real structure of the multilayer stack and by asymmetrical refraction effects. Refraction effects can be used as a powerful tool in providing highly efficient suppression of high order harmonics.

Multicolor High-Gain Free-Electron Laser Driven by Seeded Microbunching Instability.

Laser-heater systems are essential tools to control and optimize high-gain free-electron lasers (FELs) working in the x-ray wavelength range. Indeed, these systems induce a controllable increase of the energy spread of the electron bunch. The heating suppresses longitudinal microbunching instability which otherwise would limit the FEL performance. Here, we demonstrate that, through the action of the microbunching instability, a long-wavelength modulation of the electron beam induced by the laser heater at low energy can persist until the beam entrance into the undulators. This coherent longitudinal modulation is exploited to control the FEL spectral properties, in particular, multicolor extreme-ultraviolet FEL pulses can be generated through a frequency mixing of the modulations produced by the laser heater and the seed laser in the electron beam. We present an experimental demonstration of this novel configuration carried out at the FERMI FEL.

Coherence properties of the radiation from FLASH

Free electron LASer in Hamburg is the first free electron laser user facility operating in the vacuum ultraviolet and soft X-ray wavelength range. Many user experiments require knowledge of the spatial and temporal coherence properties of the radiation. In this paper, we present a theoretical analysis of the coherence properties of the radiation for the fundamental and for the higher odd frequency harmonics. We show that temporal and spatial coherence reach their maxima close to the free electron laser (FEL) saturation but may degrade significantly in the post-saturation regime. We also find that the pointing stability of short FEL pulses is limited due to the fact that nonazimuthal FEL eigenmodes are not sufficiently suppressed. We discuss possible ways for improving the degree of transverse coherence and the pointing stability.

Fabrication and characterization of free-standing, high-line-density transmission gratings for the vacuum UV to soft X-ray range.

We present state-of-the-art high resolution transmission gratings, applicable for spectroscopy in the vacuum ultraviolet (VUV) and the soft X-ray (SRX) wavelength range, fabricated with a novel process using ultraviolet based nano imprint lithography (UV-NIL). Free-standing, high-line-density gratings with up to 10,000 lines per mm and various space-to-period ratios were fabricated. An optical characterization of the gratings was carried out in the range from 17 to 34 nm wavelength using high-harmonic generation in a capillary waveguide filled with Ne, and around 13.5 nm wavelength (from 10 to 17 nm) using a Xenon discharge plasma.

Beryllium X-ray lithography templates

A simple technique for the production of lithography templates (lithography masks) with beryllium support membranes ∼50-100 μm in thickness with different types of masking coating (in the form of metallic layers produced through electroplating or in the form of a thick (∼0.13–1.10 mm) resistive mask made from, among other things, a sensitized X-ray resist) is described. Beryllium templates are characterized by their ease of fabrication; geometrical stability; almost complete lack of fluorescent radiation; low cost price; and high mechanical strength, radiation resistance, and X-ray transparency of the support membrane. Therefore, these templates may be used not only in the range of ultrashort X-ray wavelengths (0.5–3.0 A), but also in the 3–7 A range. Photographs of the first samples of such templates and diagrams illustrating their basic lithographic parameters are presented.

The free-electron laser FLASH

FLASH at DESY, Hamburg, Germany is the first free-electron laser (FEL) operating in the extreme ultraviolet (EUV) and soft x-ray wavelength range. FLASH is a user facility providing femtosecond short pulses with an unprecedented peak and average brilliance, opening new scientific opportunities in many disciplines. The first call for user experiments has been launched in 2005. The FLASH linear accelerator is based on TESLA superconducting technology, providing several thousands of photon pulses per second to user experiments. Probing femtosecond-scale dynamics in atomic and molecular reactions using, for instance, a combination of x-ray and optical pulses in a pump and probe arrangement, as well as single-shot diffraction imaging of biological objects and molecules, are typical experiments performed at the facility. We give an overview of the FLASH facility, and describe the basic principles of the accelerator. Recently, FLASH has been extended by a second undulator beamline (FLASH2) operated in parallel to the first beamline, extending the capacity of the facility by a factor of two.

Radiation detectors based on microchannel plates for free-electron lasers

Detectors based on microchannel plates are used to detect the radiation of free-electron lasers operating in short-wavelength ranges. We present descriptions of radiation detectors for the FLASH free-electron laser (DESY, Hamburg) that operates in vacuum ultraviolet and soft X-ray wavelength ranges (4–100 nm) and detectors for the European X-ray free electron laser that is being constructed in Hamburg and is designed to operate in the X-ray wavelength range from 0.05 to 4.3 nm.

The generation, characterization and applications of broadband isolated attosecond pulses

The generation of extremely short isolated attosecond pulses requires both a broad spectral bandwidth and control of the spectral phase. Rapid progress has been made in both aspects, leading to the generation of light pulses as short as 67 as in 2012, and broadband attosecond continua covering a wide range of extreme ultraviolet and soft X-ray wavelengths. Such pulses have been successfully applied in photoelectron and photoion spectroscopy and recently developed attosecond transient absorption spectroscopy to study electron dynamics in matter. In this Review, we discuss significant recent advances in the generation, characterization and applications of ultrabroadband, isolated attosecond pulses with spectral bandwidths comparable to the central frequency. These pulses can in principle be compressed to a single optical cycle. This review discusses significant recent advances in the generation, characterization and application of ultrabroadband isolated attosecond pulses with a spectral bandwidth comparable to the central frequency, which can in principle be compressed to a single optical cycle.

CORONIUM IN THE LABORATORY: MEASURING THE Fe XIV GREEN CORONAL LINE BY LASER SPECTROSCOPY

The green coronal line at 530.3 nm was first observed during the total solar eclipse of 1869. Once identified as emitted by Fe XIV, it became clear that this highly charged ion was typical for the range of temperatures found in coronal plasmas, stellar winds, outflows, and accretion disks. Under these conditions of high ionization, the strongest transitions are in the X-ray, extreme ultraviolet, and ultraviolet wavelength range, with only few optical lines. For these so-called forbidden coronal lines, only scarce laboratory data is available, and even advanced atomic theory codes cannot yet predict their wavelengths with the accuracy required for precise absolute velocity determinations of such plasmas. Here we report on a study of the Fe XIV line, a key coronal transition of a highly charged ion, using laser spectroscopy in an electron beam ion trap, obtaining the first laboratory measurement of 530.2801(4) nm for its rest wavelength. The result enables the determination of absolute line shifts and line broadenings in hot turbulent plasmas and astrophysical environments, with an error bar of only 0.24 km s–1. In addition, our measurement provides a much-needed benchmark for advanced atomic structure calculations, which are fundamental for astronomy.