Development of a tagged neutron facility for neutron scattering experiments at intermediate energies

We describe the ongoing development of a tagged neutron facility at the Ind iana University Cooler. The neutrons are produced via the interaction of a stored 200 MeV proton beam with a deuterium gas jet target. Energy and posi tion measurements of the two low-energy recoil protons in the reaction p d --> n + 2p provide the information necessary to determine the neutron fou r-momentum event by event and to thereby measure the absolute flux of neutr ons incident on the secondary target directly. The first proposed experimen t using this tagged neutron beam will be an absolute +/- 1% measurement of the np backscattering cross section.