Cold neutron microprobe for materials analysis using tapered capillary optics

A prototype monolithic capillary lens for focusing neutrons produced by the rmally drawing straight multicapillary bundles has been characterized with cold neutrons, and gives an intensity gain of a factor of 25 at a focal dis tance of 8 mm, over the focal spot area of width 87 mu m. This is over an o rder of magnitude smaller in area than for the multifiber capillary lens. T he spatial resolution available with the lens has been tested with prompt g amma measurements on slivers of dysprosium. Background problems that can af fect the spatial resolution of measurements taken at the focal position of the lens are addressed. The boron glass of the tapered monolithic lens prov ides good shielding from unfocused neutrons in the vicinity of the lens foc us. (C) 2000 American Institute of Physics. [S0034-6748(00)05109-1].