Guiding and focusing neutron beams using capillary optics

A METHOD for focusing X-rays by means of internal reflection inside hollow glass capillaries1–3has also been shown to be capable of guiding a neutron beam4 and now a neutron lens using this principle has been demonstrated5,6Here we study the properties of multiple capillary fibre bundles by measuring the transmission efficiency as a function of bending radius. The fibres used are shown to bend a neutron beam through 20° in a distance of 130 mm, with a transmission of 50%. A simple device made of a few fibres is used to demonstrate the focusing of cold neutrons (wavelength 0.2–0.9 mm) down to a 1-mm2spot size. These investigations will form the basis for the design of a neutron lens for use in materials research, or a beam bender capable of dividing and directing a neutron beam towards several experimental stations.