Fabrication of plano-elliptical neutron focusing supermirror by numerically controlled local wet etching with ion beam sputter deposition

Abstract

High-performance optical devices with a figure accuracy of sub-micrometer level and a surface roughness of atomic level are required to collect and/or to focus a neutron on a sample without scattering loss. To fabricate a high-performance neutron focusing supermirror, a two-stage numerically controlled local wet etching technique combined ion beam sputter deposition was developed. By applying this technique, a plano-elliptical substrate made of synthesized quartz glass with a figure accuracy of less than 0.5 μm was fabricated, and its surface was deposited with NiC/Ti multilayers by ion beam sputtering to produce an m=4 supermirror. The focusing performance of the supermirror was evaluated at the SUIREN of JRR-3M, and a focusing gain of 6 in peak intensity was achieved compared with a nonfocused direct beam.