Efficient and precise fabrication of Wolter type-I x-ray mirrors via nickel electroforming replication using quartz glass mandrels.

This study presents an approach for fabricating Wolter type-I mirrors for x-ray telescopes using a nickel electroforming replication process with quartz glass mandrels. The proposed method addresses the challenges encountered in conventional fabrication techniques, which involve using electroless nickel-coated aluminum mandrels that are susceptible to corrosion and thermal deformation. Quartz glass mandrels offer excellent chemical, thermal, and mechanical stability, enabling the efficient production of high-performance mirrors. Wolter type-I mirrors for telescopes possess a large aperture that collects x-ray photons from the universe. However, previous nickel electroforming replication processes using quartz glass mandrels have challenges in fabricating large mirrors, particularly due to bubble pit formation during nickel shell development. In this study, we introduced an efficient pitting inhibition technique via vacuum degassing. This technique facilitates the precise replication of pit-free Wolter type-I mirrors for telescopes using quartz glass mandrels. We demonstrated the fabrication process on a Wolter type-I mirror proposed for FOXSI-4 [(FOXSI) Focusing Optics X-ray Solar Imager], resulting in three mirrors obtained from the same mandrel without repolishing or repairing. The figure error of the mirror was within 1 µm over most areas in both longitudinal and circumferential directions. The ray-tracing simulation indicated that the performance of the mirror was ∼12 arcsec in half-power diameter, comparable to the performance achieved by previous high-resolution x-ray missions.

Figure correction of a Wolter mirror master mandrel by organic abrasive machining.

In this study, figure correction of a master mandrel of a Wolter mirror by organic abrasive machining (OAM) was demonstrated. In OAM, a flow of slurry, dispersed with organic particles, locally removes the surface of a workpiece in contact with a rotating machining tool. A computer-controlled machining system was used to perform the selective removal of a fused silica surface at a spatial resolution of 200 µm. A master mandrel of a Wolter mirror for soft x-ray microscopes was fabricated with a figure accuracy of <1 nm root mean square, which is sufficient for diffraction-limited imaging at a wavelength of 10 nm.

Fabrication of soft x-ray monolithic Wolter mirror based on surface scanning measurement using touch probe.

The monolithic Wolter mirror is an ideal optical device for focusing soft x rays to a submicron-sized spot, with the advantages of high efficiency, large acceptance, achromaticity, and robustness to alignment error. The fabrication process for this type of mirror has not been established because of the difficulty in highly accurate figure measurement of free-form surfaces with small radii of curvature and steep profiles. In this study, we employed tactile scanning measurement for surface characterization to fabricate a high-precision Wolter mirror. First, it was demonstrated that the touch probe measurement did not leave scratches on the raw surface of the mirror substrate. Next, the measurement capability of the surface profiler was assessed, and the data analysis conditions were determined. Finally, the Wolter mirror was fabricated through repeated figure correction based on the tactile measurement, and the figure error of the final surface was evaluated. Wave-optical simulations that used this error as reference suggested that the size of the beam focused by the mirror was equivalent to the theoretical value at 1000 eV. The reflected image with uniform intensity distribution obtained at SPring-8 also revealed the effectiveness of the present fabrication approach based on tactile measurement.

Organic abrasive machining system for optical fabrication with 0.1-mm spatial resolution.

High-precision optics for short-wavelength regions, such as x rays and extreme ultraviolet light, generally require nanometer-level figure accuracy on their surfaces. Such optics are finished via a numerically controlled figure correction process in which the dwelling time of the machining tool on the workpiece is controlled. Due to the limitation of the machined spot size, it is difficult to remove mid-spatial-frequency (1 to 10 mm-1) errors on an optical surface. To realize a high-spatial-resolution figure correction process for high-precision optics, we have been developing the organic abrasive machining (OAM) technique, which can generate a 100 µm machined spot using a small elastic rotation tool in a slurry that includes acrylic particles. In this study, an OAM apparatus that can measure the machining load was constructed. The effects of the machining and slurry conditions were investigated and high-spatial-resolution machining on a flat glass substrate was demonstrated. The root-mean-square roughness of the surface after OAM processing was below 0.2 nm. Patterns with a minimum line and space size of 100 µm were successfully fabricated.

Harimaru: a new potato variety for a local specialty.

'Harimaru' is a new potato variety bred from a cross between 'Saikai 35' as a female parent and 'Pike' as a male parent. Marker selection was performed for 1,647 seedlings to combine resistance genes to late blight (R1), Potato virus Y (Rychc ), Potato virus X (Rx1), and golden cyst nematode (H1). In total, 194 selected clones were evaluated in the field, among which the best clone was officially released as 'Harimaru'. Its yield was slightly lower than the local standard variety, 'May Queen'. However, it produces tasty potatoes, that do not become mushy with long boiling times despite its high starch content. 'Harimaru' may become a local specialty potato and its multiple resistance to potato viruses may allow cultivation using homemade seed tubers from the previous season's crop.

Synthesis of Four Chiral Isomers of beta-Lactone DU-6622 and Inhibition of HMG-CoA Synthase by the Specific (2R,3R)-Isomer.

Four chiral forms of the beta-lactone DU-6622 (3-hydroxy-2-(hydroxymethyl)-5-[7-(methoxycarbonyl)naphthalen-1-yl]pentanoic acid 1,3-lactone) were prepared to investigate their inhibitory activity against 3-hydroxy-3-methylglutarly-CoA (HMG-CoA) synthase. The (2R,3R)-beta-lactone isomer (+)-8a, having the same stereochemistry as that of the fungal beta-lactone 1233A, showed the most potent HMG-CoA synthase inhibitory activity (IC(50): 0.098 &mgr;M). The other three beta-lactone isomers, (2S,3R)- ((-)-8b), (2S,3S)- ((-)-8a), and (2R,3S)-isomers ((+)-8b), were weaker inhibitors with larger IC(50) values of 9.4, 31, and 360 &mgr;M, respectively. Thus, it was concluded that the (2R,3R) stereochemistry of the beta-lactone ring is responsible for HMG-CoA synthase inhibition.