Characterization of a cold neutron beam from a curved guide

A supermirror guide that includes both straight sections and curved channels has been installed at a cold neutron source facility. A description of the beam line and the beam characteristics are given. The transmitted neutron wavelength spectrum and the beam current density have been measured. Factors that affect the spectrum are discussed. Though the final straight guide section improves the spatial uniformity of the beam intensity at the guide exit, the spatial-angular correlations caused by the curved channels persist. These correlations are observed in the beam divergence measurements at various positions along the beam line using neutron imaging plate technology, and are explained by ray projections. The divergence of the transmitted beam is determined both by the critical angle of the guide and the collimation beyond the guide. (C) 1998 Elsevier Science B.V. All rights reserved.