X-ray imagery of the solar corona with arcsecond-level angular resolution is a key to understand various activities of hot plasmas in the corona. We report our development activities of precision Wolter mirrors for future soft X-ray imaging observations of the Sun. The Wolter mirrors under development are fabricated by direct polishing of glass-ceramic substrates. We fabricated an engineering Wolter mirror of 3-m focal length whose mirror area was 40 mm x 50 mm (along optical-axis and cylindrical directions, respectively) for each of the parabola and hyperbola sections using EEM (Elastic Emission Machining) precision polishing technology. X-ray imaging performance of the mirror was then evaluated with 8-keV parallel X-rays at SPring-8/BL29XUL. For the mirror area whose tilt up to >6 degrees along the cylindrical direction, the mirror showed imaging performance of ~0.25 arcsec FWHM (~0.55 arcsec HPD) with the scattering level ~1 × 10-4 of the PSF peak at 30-arcsec off-axis position.
Recently two-dimensional curved X-ray mirrors such as ellipsoidal and rotational Wolter mirrors have become widely used at synchrotron radiation facilities. Although microstitching interferometry (MSI) can measure surface figures, it takes a long time to obtain surface figure data because of the small field of view for a steeply curved surface. To improve productivity, we are developing a high throughput CGH (Computer Generated Hologram) interferometer system. To fit the CGH wavefront to the mirror surface, we use cylindrical wavefront CGHs for the interferometer system, as part of two-dimensional curved X-ray mirrors that can be approximated by a cylindrical surface. We will give a developing status of our CGH interferometer system.
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