Neutron absorption measurements using converging beams – increased reaction rate

Focusing lenses using neutron reflection optics may considerably increase the neutron beam current density over a small area. The technique enables neutron absorption measurements to be taken with higher sensitivity, greater spatial resolution and lower background. Experimental concerns associated with the beam converging onto the sample are considered and compared to those for a quasi-parallel beam. In particular, we show the connection between the interaction rates for the parallel beam and the isotropic field.