Abstract: A neutron lens constructed with glass capillary fibers has been used to focus neutron beams of various geometries and wavelengths. We give as an example measurements performed at an end position of a $+58$/Ni-coated cold neutron guide, where the exiting neutron beam with a cross section of 30 mm in diameter from the guide is incident on the lens and is focused to a 1 mm diameter spot, with a gain of 3.6 in neutron flux density. We have evaluated various features of the focusing performance of the lens, as well as some neutron properties of individual capillary fibers. The average reflectivity of the inner wall of the fibers has been determined to be greater than 0.99. The results of this study will be used for the design and construction of future lenses for neutron absorption experiments such as depth profiling and prompt gamma activation analysis.!9
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