Toward the fabrication of a 5-µm-resolution Wolter microscope for the National Ignition Facility (invited).

Advancements in computer-controlled polishing, metrology, and replication have led to an x-ray mirror fabrication process that is capable of producing high-resolution Wolter microscopes. We present the fabrication and test of a nickel-cobalt replicated full-shell x-ray mirror that was electroformed from a finely figured and polished mandrel. This mandrel was designed for an 8-m source-to-detector-distance microscope, with 10× magnification, and was optimized to reduce shell distortions that occur within 20 mm of the shell ends. This, in combination with an improved replication tooling design and refined bath parameters informed by a detailed COMSOL Multiphysics® model, has led to reductions in replication errors in the mirrors. Mandrel surface fabrication was improved by implementing a computer-controlled polishing process that corrected the low-frequency mandrel figure error and achieved <2.0 nm RMS convergence error. X-ray tests performed on a pair of mirror shells replicated from the mandrel have demonstrated <10 µm full-width at half-maximum (FWHM) spatial resolution. Here, we discuss the development process, highlight results from metrology and x-ray testing, and define a path for achieving a program goal of 5 µm FWHM resolution.

Full-shell x-ray optics development at NASA Marshall Space Flight Center.

NASA's Marshall Space Flight Center (MSFC) maintains an active research program toward the development of high-resolution, lightweight, grazing-incidence x-ray optics to serve the needs of future x-ray astronomy missions such as Lynx. MSFC development efforts include both direct fabrication (diamond turning and deterministic computer-controlled polishing) of mirror shells and replication of mirror shells (from figured, polished mandrels). Both techniques produce full-circumference monolithic (primary + secondary) shells that share the advantages of inherent stability, ease of assembly, and low production cost. However, to achieve high-angular resolution, MSFC is exploring significant technology advances needed to control sources of figure error including fabrication- and coating-induced stresses and mounting-induced distortions.

X-ray reflectometer for single layer and multilayer coating characterization at 8 keV: An interlaboratory study.

An X-ray reflectometer (XRR) system has been developed at the Marshall Space Flight Center (MSFC) for characterizing various soft and hard X-ray optic coatings. The XRR instrument generates X-ray radiation using a high-output rotating anode source (RAS), operational over a voltage range of 5-35 kV and a current range of 10-150 mA. Copper is used as the target material to produce an X-ray spectrum from which the Kα line at 8.048 keV is isolated for the reflectivity measurements. Five precision slits are mounted along the X-ray beam path to limit the extent of the beam at the sample and to adjust the resolution in the measurements. A goniometer consisting of two precision rotary stages controls the positions of the coating sample and the X-ray detector with respect to the beam. The detector itself is a high performance silicon drift detector used to achieve high count rate efficiency to attain good statistics in the reflectivity measurement at larger grazing angles. The X-ray reflectometer system design and capabilities are described in detail. Verification of the system is obtained through an interlaboratory study in which reflectivity measurements of a multilayer coating made at MSFC are compared with those made at two external laboratories.

Demonstration of a novel focusing small-angle neutron scattering instrument equipped with axisymmetric mirrors.

Small-angle neutron scattering (SANS) is the most significant neutron technique in terms of impact on science and engineering. However, the basic design of SANS facilities has not changed since the technique's inception about 40 years ago, as all SANS instruments, save a few, are still designed as pinhole cameras. Here we demonstrate a novel concept for a SANS instrument based on axisymmetric focusing mirrors. We build and test a small prototype, which shows a performance comparable to that of conventional large SANS facilities. By using a detector with 48-µm pixels, we build the most compact SANS instrument in the world. This work, together with the recent demonstration that such mirrors could increase the signal rate at least 50-fold, for large samples, while improving resolution, paves the way to novel SANS instruments, thus affecting a broad community of scientists and engineers.