Atomically smooth surfaces as substrates for advanced neutron supermirrors

Neutron scattering facilities are a key resource aiding the diverse and growing revolution in nano-science and technology-An ongoing challenge for these facilities is providing sufficient neutron flux for an acceptable signal-to-noise ratio for ever more precise experiments-Presently much of the neutron flux is lost because of inefficiencies in the hundreds of meters beam guides and other optics- Reflecting and focusing neutrons requires optical surfaces that smooth to the level of atomic dimensions (»1 Å)-This level of smoothness is extremely difficult, time-consuming, costly, and often impossible to achieve using conventional mechanical polishing methods, particularly when smoothing the metallic substrates and the 3-demensionally curved surfaces that are most desired for this application- The goal of our project is to produce two advanced neutron optics for Oak Ridge National Laboratories’ neutron scattering facilities- The first optic will be immediately upstream of the experimental stations and will require a complex 3-dimensional curvature to focus the neutron beam in both dimensions to a small spot-size that will allow the use of smaller sample sizes and pressure cells- The second optic will be used near the spallation neutron target or the reactor core, where the flux of high-energy neutrons is greatest, to increase the lifetime of these optics and to allow greater shielding from the high-energy neutrons- This optic will use a novel substrate material such as stainless steel- American Physics and Technology will apply two innovative new surface nano-smoothing technologies based on using high-energy, focused beams of nano-scale cluster ions to bombard the surface for the critical final smoothing steps required to produce the desired 1 Å surface finish- In phase I will demonstrate the cluster ion beam technology and produce a preliminary design of the two optics and the method of manufacturing them-