The Cornell University cold neutron beam facility

A cold neutron beam facility nearing completion at the Cornell University 500-kW TRIGA Mark 2 reactor is described. Designed to optimize beam quality for basic and applied research in which low backgrounds are especially important, it uses a cold neutron source in the reactor reflector and a curved 13-m neutron guide. The only operating US cold sources are at Brookhaven and NIST and emphasize long-wavelength neutrons for condensed matter research. The authors' system has a different purpose: a nearly pure subthermal beam with no fast neutrons or gamma rays and a target station remote from other experiments. Cold sources are generally considered to be complex, costly and hazardous. For a medium power university reactor the authors chose mesitylene as a proven cold moderator safer than hydrogen or methane and cool it with copper cold fingers instead of circulating helium gas. Design details, initial operating tests, and experimental plans are described