NEUTRON FOCUSING LENS USING POLYCAPILLARY FIBERS

Multiple mirror reflection at small grazing angles from the smooth sur faces of the narrow channels of polycapillary fibers can be used to tr ansport, bend, and focus thermal neutron beams. We report the results of the focusing of a polychromatic cold neutron beam using a compact l ens of borosilicate fibers and with a focal distance of 57 mm. The int ensity profile of the beam at the focus is approximately conical in sh ape with a full width at half-maximum of 0.49 mm, and with an average gain in intensity of about 20. These experimental results agree well w ith those obtained by computer simulation.