An experimental setup for studying neutron-neutron final state interaction on the neutron channel of the Moscow Meson Factory

A setup for measuring the singlet nn-scattering length in the n + d → p + n + n reaction is described. It is composed of a neutron hodoscope with an angular aperture of 12° and a scintillation detector for protons escaping at an angle of 90° with the beam direction. The exit angles and the energies of a proton and both neutrons are measured. The neutron energies are measured using the time-of-flight method. At a time resolution of ∼0.6 ns and a flight base of ∼5.5 m, the accuracy in measuring the neutron energy is ∼1% at an energy of ∼15 MeV. The dependence of the reaction yield on the relative energy of two neutrons is investigated. The neutron-neutron final-state interaction manifests itself as a peak in this distribution.