CHARACTERIZATION OF A COLD NEUTRON BEAM FROM A CURVED GUIDE

A supermirror guide that includes both straight sections and curved ch annels has been installed at a cold neutron source facility. A descrip tion of the beam line and the beam characteristics are given. The tran smitted 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 th e beam intensity at the guide exit, the spatial-angular correlations c aused by the curved channels persist. These correlations are observed in the beam divergence measurements at various positions along the bea m line using neutron imaging plate technology, and are explained by ra y projections. The divergence of the transmitted beam is determined bo th by the critical angle of the guide and the collimation beyond the g uide. (C) 1998 Elsevier Science B.V. All rights reserved.