Design of a TOF-SANS instrument for the proposed long-wavelength target station at the spallation neutron source

We have designed a versatile high-data-rate SANS instrument (broad-range intense multipurpose SANS (BRIMS)) for the proposed long-wavelength target station at the SNS using the Los Alamos NISP Monte Carlo simulation package. BRIMS is designed to produce data spanning a Q range from 0.0025 to 0.7 Å^-1 in a single measurement by simultaneously using neutrons with wavelengths from 1 to 14.5 Å in a time-of-flight mode. The effects of various collimation choices, including multiple confocal pinhole apertures, on count rate, resolution, and Q range have been characterized with simulations using spherical particle and delta-function scatterers. We compare the anticipated performance of BRIMS with that of the premier reactor-based SANS instrument, D22, at ILL.