Neutron absorption measurements using converging beams - increased reaction rate

Focusing lenses using neutron reflection optics may considerably increase t he neutron beam current density over a small area. The technique enables ne utron absorption measurements to be taken with higher sensitivity, greater spatial resolution and lower background. Experimental concerns associated w ith the beam converging onto the sample are considered and compared to thos e for a quasi-parallel beam. In particular, we show the connection between the interaction rates for the parallel beam and the isotropic held. (C) 199 9 Elsevier Science B.V. All rights reserved.