We have developed a Fresnel-type focusing device for cold neutrons fabricated using single crystals of magnesium fluoride. This stacked-lens device using 50 elements (with 50 beam-bending interfaces) demonstrated a focal length of 5 m with a good transmission of 0.829 for 1.14 nm neutrons. The focused beam was 5 times more intense than a beam of the same spot size with the same final flight path length produced with the traditional pinhole collimation. The background-scattering noise from lens was an order of magnitude larger than that of the traditional pinhole collimation in the momentum range of 0.01-0.05 nm-1, almost 10-3 of focused direct beam at the lowest momentum transfers measurable. This device produced an intensity gain in measured SANS data of more than 10 times when compared with the conventional pinhole geometry with the same minimum momentum transfer.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering