A High Transmission Slow Neutron Velocity Selector

Abstract
A high intensity neutron monochromator for the subthermal energy region is described. The instrument utilizes the velocity selectivity of a rotating helix. A complete analysis is made of the instrument resolution for several practical constructions. For wavelengths longer than one angstrom, a mechanical selector may yield resolutions of 1.0 to 0.1 and fractional transmissions of 60 percent. Design and tests of a selector are described and compared with the theory.