Silicon Microchannel Neutron Lens

The Department of Energy supports large-scale, national user facilities that generate intense neutron beams for the characterization of materials. Increasingly used in research, neutrons are making invaluable contributions to the physical, chemical, and biological sciences. Despite advances in neutron sources and instrumentation, many neutron scattering experiments remain flux limited. Improved focusing optics would enhance neutron flux density in samples, significantly reducing data collection time. This project will develop a compound silicon microchannel neutron lens with a geometrically ideal microchannel structure. The proposed microchannel ¿lobster eye¿ lens will focus neutrons into an approximately 0.1 millimeter spot, with much greater efficiency than conventional neutron lenses. In Phase I, the lens design was optimized, based on a lobster eye assembly of flat metal-plated silicon wafers; a functional lens prototype was fabricated; and proof-of-concept was demonstrated by focusing hard x-rays (30 kiloelectronvolt peak) to a less than 1 millimeter focal spot. In Phase II, a fully operational, large-scale, silicon microchannel, neutron focusing and radial collimation device will be developed, initiating a new class of neutron optics for stress, texture, and other analysis of advanced materials in small volumes by neutron diffraction. The device will be based on silicon elements coated with nickel/titanium supermirrors and assembled into microchannel structures with high-aspect-ratio channels (1:1250). The device will be specifically designed for government diffractometers, where it will be rigorously tested as part of the Phase II project. Commercial Applications and other Benefits as described by the awardee: Besides the applications for unique instrumentation in national laboratories, the proposed lens should find use in the next generation of neutron microscopes now under development. Such microscopes, with spatial resolution far beyond the limits of visible light microscopy, are urgently needed for submicron photolithography and for biomedical research on cell structures. Other applications include homeland security screening systems and industrial nondestructive evaluation.