Neutron collimator with rectangular beam profile

Several Seller slit-type neutron collimators which give rectangular profile s of transmission as a function of angular divergence have been constructed . The collimators accept a beam of realistic dimensions - greater than 12 x 22 mm(2) in all cases. The blades of the collimators are 280 mum thick waf ers of single-crystal silicon each coated with a Ni-Gd-Ni multilayer on one side. Tests at a neutron wavelength of 7.5 Angstrom confirm that the trans mission profiles are rectangular. Tests at a wavelength of 4.2 Angstrom sho w that two such collimators rocked against each other give dramatically enh anced transmission and resolution by comparison with conventional collimato rs. This is the first such demonstration of increased counting rates in a s can on an instrument from rectangular profile collimators, an effect expect ed but not produced for over 40 years. (C) 2001 Elsevier Science B.V, All r ights reserved.