The present calculations describing the Bonse-Hart Ultra-Small-Angle Neutron Scattering (USANS) Instrument with triple-bounce Si channel-cut crystals show that significant gains in neutron flux and Q-resolution can be achieved using multiple high-order Bragg reflections. These reflections become usable only after combining the Bonse-Hart and Time-of-Flight techniques, thus this variant of the USANS camera needs a pulsed neutron source. We clearly demonstrate that new instruments of that type installed at the SNS water moderator will improve the current state-of-the art USANS camera dramatically increasing the neutron flux and sharpening the Q-resolution by almost one order of magnitude.
It was recently proposed (by Dombeck et al) to search for a Neutron Electric Dipole Moment (EDM) by means of the neutron multiple Bragg back-scattering. The dynamical diffraction analysis of the proposed experiment is the subject of this paper. The neutron wave modes were calculated for the case of the infinitely long slot cut inside of a thick Si crystal parallel to the crystallographic planes and placed in a steady magnetic field. The calculated neutron modes have a discrete spectrum of a momenta along the direction of the slot axis. The external magnetic field causes some particular discrete modes to become degenerate. However, the Schwinger and EDM interactions of neutrons with the slot walls break this degeneracy, which in turn leads to the complicated motion of the neutron polarization vector along the slot axis. The spin deviation from the starting direction is accumulated during neutron motion in slot. The energy spectrum of neutrons transmitted through the slot contains several peaks instead of one existing for the case of the ultra back-scattering regime.
Next-generation spallation neutron source facilities will offer instruments with unprecedented capabilities through simultaneous enhancement of source power and usage of advanced optical components. The Spallation Neutron Source (SNS), already under construction at Oak Ridge National Laboratory and scheduled to be completed by 2006, will provide greater than an order of magnitude more effective source flux than current state-of-the-art facilities, including the most advanced research reactors. An additional order of magnitude gain is expected through the use of new optical devices and instrumentation concepts. Many instrument designs require supermirror (SM) neutron guides with very high critical angles for total reflection. In this contribution, we will discuss how the performance of modern neutron scattering instruments depends on the efficiency of these supermirrors. We outline ideas for enhancing the performance of the SM coatings, particularly for improving the reflectivity at the position of the critical wave vector transfer. A simulation program has been developed which allows different approaches for SM designs to be studied. Possible instrument performance gains are calculated for the example of the SNS reflectometer.