Achromatic nested Kirkpatrick–Baez mirror optics for hard X-ray nanofocusing

Abstract

The first test of nanoscale-focusing Kirkpatrick-Baez (KB) mirrors in the nested (or Montel) configuration used at a hard X-ray synchrotron beamline is reported. The two mirrors are both 40 mm long and coated with Pt to produce a focal length of 60 mm at 3 mrad incident angle, and collect up to a 120 mm by 120 mm incident X-ray beam with maximum angular acceptance of 2 mrad and a broad bandwidth of energies up to 30 keV. In an initial test a focal spot of about 150 nm in both horizontal and vertical directions was achieved with either polychromatic or monochromatic beam. The nested mirror geometry, with two mirrors mounted side-by-side and perpendicular to each other, is significantly more compact and provides higher demagnification than the traditional sequential KB mirror arrangement. Ultimately, nested mirrors can focus larger divergence to improve the diffraction limit of achromatic optics. A major challenge with the fabrication of the required mirrors is the need for nearperfect mirror surfaces near the edge of at least one of the mirrors. Special polishing procedures and surface profile coating were used to preserve the mirror surface quality at the reflecting edge. Further developments aimed at achieving diffraction-limited focusing below 50 nm are underway.

Progress of nanopositioning stages development for hard x-ray nanofocusing and coherence preservation optics at the APS

“…To meet challenging mechanical and optical specifications for producing high positioning resolution and stability with focused hard x-ray beams down to the 100-nanometer scale, modular K-B mirror mount system using flexural-pivots-based structures for hard x-ray microfocusing applications were built at the APS as shown in Figure 1a and 1b [2]. To meet the demanding mechanical specifications with 20-nrad tip-tilting resolution for hard x-ray mirror focusing at the sub-50-nanometer-scale, a multidimensional flexure stage system using high-stiffness laminar weak-link mechanism has been developed for the APS 34-ID-E experimental station for 3-D nano-diffraction applications as shown in Figure 1c and 1d [3]. …”

Multimodal hard x-ray nanoprobe facility by nested Montel mirrors aimed for 40nm resolution at Taiwan Photon Source

“…The numerical aperture is thus improved, and a smaller diffraction-limit focal spot is obtained. In literature, the Montel mirrors are placed at 90 degree cut, for the sake of easier alignment 3 . However, an unavoidable gap between the two ellipse mirror surfaces causes a delivery loss of photon flux, as shown in Fig.…”

Plastic Deformation in Profile-Coated Elliptical KB Mirrors

“…Sub-100-nm focusing has been demonstrated using a synchrotron X-ray beamline [5]. Nested KB mirrors have also been successfully fabricated [6,7]. One serious concern of X-ray mirrors is their long-term figure stability.…”