Characterization of a ballistic supermirror neutron guide

Abstract We describe the beam characteristics of the first ballistic supermirror neutron guide H113 that feeds the neutron user facility for particle physics PF1B of the Institute Laue-Langevin, Grenoble (ILL). At present, the neutron capture flux density of H113 at its 20×6 cm 2 exit window is Φ C = 1.35 × 1 0 10 cm - 2 s - 1 , and will soon be raised to above 2×10 10 cm −2 s −1 . Beam divergence is no larger than beam divergence from a conventional Ni-coated guide. A model is developed that permits rapid calculation of beam profiles and absolute event rates from such a beam. We propose a procedure that permits inter-comparability of the main features of beams emitted from ballistic or conventional neutron guides.