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The third flight of the High-Resolution Coronal Imager (Hi-C 2.1) occurred on May 29, 2018, the Sounding Rocket was launched from White Sands Missile Range in New Mexico. The instrument has been modified from its original configuration (Hi-C 1) to observe the solar corona in a passband that peaks near 172 Angstrom and uses a new, custom-built low-noise camera. The instrument targeted Active Region 12712, and captured 78 images at a cadence of 4.4 sec (18:56:22 - 19:01:57 UT; 5 min and 35 sec observing time). The image spatial resolution varies due to quasi-periodic motion blur from the rocket; sharp images contain resolved features of at least 0.47 arcsec. There are coordinated observations from multiple ground- and space-based telescopes providing an unprecedented opportunity to observe the mass and energy coupling between the chromosphere and the corona. Details of the instrument and the data set are presented in this paper., Comment: 26 pages, 15 figures, submitted to Solar Physics

The Sun Coronal Ejection Tracker (SunCET) is an extreme ultraviolet imager and spectrograph instrument concept for tracking coronal mass ejections through the region where they experience the majority of their acceleration: the difficult-to-observe middle corona. It contains a wide field of view (0–4 R⊙) imager and a 1 Å spectral-resolution-irradiance spectrograph spanning 170–340 Å. It leverages new detector technology to read out different areas of the detector with different integration times, resulting in what we call “simultaneous high dynamic range”, as opposed to the traditional high dynamic range camera technique of subsequent full-frame images that are then combined in post-processing. This allows us to image the bright solar disk with short integration time, the middle corona with a long integration time, and the spectra with their own, independent integration time. Thus, SunCET does not require the use of an opaque or filtered occulter. SunCET is also compact – ~15 × 15 × 10 cm in volume – making it an ideal instrument for a CubeSat or a small, complementary addition to a larger mission. Indeed, SunCET is presently in a NASA-funded, competitive Phase A as a CubeSat and has also been proposed to NASA as an instrument onboard a 184 kg Mission of Opportunity.

The High-Energy X-ray Probe (HEX-P) is a probe-class next-generation high-energy X-ray mission concept that will vastly extend the reach of broadband X-ray observations. Studying the 2-200 keV energy range, HEXP has 40 times the sensitivity of any previous mission in the 10-80 keV band, and will be the first focusing instrument in the 80-200 keV band. A successor to the Nuclear Spectroscopic Telescope Array (NuSTAR), a NASA Small Explorer launched in 2012, HEX-P addresses key NASA science objectives, and will serve as an important complement to ESA's L-class Athena mission. HEX-P will utilize multilayer coated X-ray optics, and in this paper we present the details of the optical design, and discuss the multilayer prescriptions necessary for the reflection of hard X-ray photons. We consider multiple module designs with the aim of investigating the tradeoff between high- and low-energy effective area, and review the technology development necessary to reach that goal within the next decade.

We present continued development of components for measuring linear X-ray polarization over the 0.2-0.8 keV (15-62 Angstrom) band. We present results from measurements of new laterally graded multilayer mirrors and critical angle transmission gratings essential to the approach. While the lab is designed to verify components to be used in a soft X-ray polarimeter, it is reconfigurable and has been used to verify grating efficiencies with our new CCD detector. Our development work is the basis for a sounding rocket mission (Rocket Experiment Demonstration of a Soft X-ray Polarimeter) and future orbital missions.

A prototype system for breast imaging using monochromatic X-rays has been developed using a scanning multilayer X-ray mirror in combination with a conventional mammography tube and an imaging detector. The X-ray mirror produces a monochromatic fan beam tuned near 19 keV, with an energy bandpass of approximately 1.5 keV. Rotating the mirror about the tube’s focal spot in synchronization with the X-ray generator and detector enables the acquisition of monochromatic X-ray images over large areas. The X-ray mirror also can be rotated completely out of the beam so that conventional polychromatic images can be acquired using a K-edge filter, facilitating direct comparison between the two modes of operation. The system was used to image synthetic, tissue-equivalent breast phantoms in order to experimentally quantify the improvements in image quality and dose that can be realized using monochromatic radiation. Nine custom phantoms spanning a range of thicknesses and glandular/adipose ratios, each containing both glandular- and calcification-equivalent features, were used to measure contrast and signal-difference-to-noise ratio (SDNR). Mean glandular dose (MGD) was computed from measured entrance exposure, and a figure-of-merit (FOM) was computed as FOM = SDNR(2)/MGD in each case. Monochromatic MGD ranges from 0.606 to 0.134 of polychromatic MGD for images having comparable glandular SDNR, depending on breast thickness and glandularity; relative monochromatic dose decreases with increasing glandularity for all thicknesses. Monochromatic FOM values are higher than the corresponding polychromatic FOM values in all but one case. Additionally, the monochromatic contrast for glandular features is higher than the polychromatic contrast in all but one case as well. These results represent important steps toward the realization of clinically practical monochromatic X-ray breast imaging systems having lower dose and better image quality, including those for digital mammography, digital breast tomosynthesis, contrast-enhanced spectral mammography and other modalities, for safer, more accurate breast cancer detection, diagnosis and staging.

We describe an optical design and possible implementation of a broadband soft x-ray polarimeter. Our arrangement of gratings is designed optimally for the purpose of polarimetry with broadband focusing optics by matching the dispersion of the spectrometer channels to laterally graded multilayers (LGMLs). The system can achieve polarization modulation factors over 90%. We implement this design using a single optical system by dividing the entrance aperture into six sectors; high efficiency, blazed gratings from opposite sectors are oriented to disperse to a common LGML forming three channels covering the wavelength range from 35 to 75 Å (165 to 350 eV). The grating dispersions and LGML position angles for each channel are 120 deg to each other. CCD detectors then measure the intensities of the dispersed spectra after reflection and polarizing by the LGMLs, giving the three Stokes parameters needed to determine a source's linear polarization fraction and orientation. The design can be extended to higher energies as LGMLs are developed further. We describe examples of the potential scientific return from instruments based on this design.

In order to advance significantly scientific objectives, future x-ray astronomy missions will likely call for x-ray telescopes with large aperture areas (≍ 3 m2) and fine angular resolution (≍ 12). Achieving such performance is programmatically and technologically challenging due to the mass and envelope constraints of space-borne telescopes and to the need for densely nested grazing-incidence optics. Such an x-ray telescope will require precision fabrication, alignment, mounting, and assembly of large areas (≍ 600 m2) of lightweight (≍ 2 kg/m2 areal density) high-quality mirrors, at an acceptable cost (≍ 1 M$/m2 of mirror surface area). This paper reviews relevant programmatic and technological issues, as well as possible approaches for addressing these issues-including direct fabrication of monocrystalline silicon mirrors, active (in-space adjustable) figure correction of replicated mirrors, static post-fabrication correction using ion implantation, differential erosion or deposition, and coating-stress manipulation of thin substrates....

This paper describes recent progress in the development of new EUV multilayer coatings for solar physics. In particular, we present results obtained with Pd/B4C/Y, Al/Zr, and Al-Mg/SiC multilayers, designed for normal incidence operation in the 9 – 50 nm wavelength range. We describe the development of both periodic multilayer films designed for narrowband imaging, and non-periodic multilayers designed to have a broad-spectral response for spectroscopy. The higher EUV reflectance provided by these new coatings, relative to older-generation coatings such as Si/Mo, Mo/Y, and others, will facilitate the development of future solar physics instruments for both imaging and spectroscopy having higher spatial and spectral resolution, while supporting the exposure times and cadences necessary to capture the evolution of flares, jets, CMEs and other dynamic processes in the solar atmosphere.

This paper is focused on recent progress in the development of broad-band multilayer coatings designed for hard X-ray energies, for use in future astronomical telescopes. We describe a new laboratory-based hard X-ray reflectometer for atwavelength characterization of multilayer films, we present the results of an experimental comparison of the hard X-ray performance of several W-based periodic multilayer coatings, and we describe the optimization and experimental performance of new non-periodic Co-based multilayer coatings (both depth-graded and aperiodic), designed for continuous response through the W and Pt K-edges near 70 and 80 keV, respectively. We discuss future research directions in light of these new results.

This paper describes a new variation of the differential deposition/differential erosion technique for mid-frequency surface-height error correction. In our approach, the technique is extended to two dimensions in order to correct surfaceheight errors in thin-shell cylindrical mirror segments with high throughput. We describe the new infrastructure currently being developed to realize this technique, including an LTP system for surface metrology of mid-frequency surfaceheight errors, a new UHV linear stage for precise substrate motion during deposition or erosion, and most crucially, the development of electronically-actuated aperture arrays that are mounted in front of a rectangular magnetron cathode, or a rectangular ion source, in order to modulate the deposition/erosion rate of material in two dimensions, in real-time.

A laboratory-based X-ray reflectometer has been developed to measure the performance of hard X-ray multilayer coatings at their operational X-ray energies and incidence angles. The instrument uses a sealed-tube X-ray source with a tungsten anode that can operate up to 160 kV to provide usable radiation in the 15–150 keV energy band. Two sets of adjustable tungsten carbide slit assemblies, spaced 4.1 m apart, are used to produce a low-divergence white beam, typically set to 40 μm × 800 μm in size at the sample. Multilayer coatings under test are held flat using a vacuum chuck and are mounted at the center of a high-resolution goniometer used for precise angular positioning of the sample and detector; additionally, motorized linear stages provide both vertical and horizontal adjustments of the sample position relative to the incident beam. A CdTe energy-sensitive detector, located behind a third adjustable slit, is used in conjunction with pulse-shaping electronics and a multi-channel analyzer to capture both the incident and reflected spectra; the absolute reflectance of the coating under test is computed as the ratio of the two spectra. The instrument’s design, construction, and operation are described in detail, and example results are presented obtained with both periodic, narrow-band and depth-graded, wide-band hard X-ray multilayer coatings.

A new extreme ultraviolet (EUV) multilayer coating has been developed comprising Pd and Y layers with thin B4C barrier layers at each interface, for normal incidence applications near 10 nm wavelength. Periodic, nonperiodic, and dual-stack coatings have been investigated and compared with similar structures comprising either Mo/Y or Pd/B4C bilayers. We find that Pd/B4C/Y multilayers provide higher reflectance than either Mo/Y or Pd/B4C, with much lower film stress than Pd/B4C. We have also investigated the performance of periodic multilayers comprising repetitions of Pd/Y, Ru/Y, or Ru/B4C/Y, as well as Pd/B4C multilayers deposited using reactive sputtering with an Ar:N2 gas mixture in order to reduce stress: these material combinations were all found to provide poor EUV performance. The temporal stability of a periodic Pd/B4C/Y multilayer stored in air was investigated over a period of 16 months, and a slight reduction in peak reflectance was observed. Periodic Pd/B4C/Y multilayers were also found to be thermally stable up to 100°C; at higher temperatures (200°C and 300°C) we observe a slight reduction in peak reflectance and a slight increase in multilayer period. High-resolution transmission electron microscopy and selected area diffraction of an as-deposited Pd/B4C/Y film indicates a fully amorphous structure, with interfaces that are both smoother and more abrupt than those observed in a comparable Pd/B4C multilayer in which the Pd layers are polycrystalline. The new Pd/B4C/Y multilayers are suitable for normal-incidence imaging and spectroscopy applications, including solar physics, plasma physics, high-brightness EUV light sources, and others.