A Focusing Test of a Multiple Segmented Ellipsoidal Neutron-Focusing Mirror for a Compact-Focusing SANS Instrument

Abstract

A 300 mm long metallic neutron focusing mirror with an ellipsoidal figure was designed and manufactured for a compact focusing small angle neutron scattering (SANS) instrument. The ellipsoidal figure was designed to have focal length of 2.5 m. The mirror consists of three mirror segments each plated with electroless NiP fixed to a base plate. The curved surface of the mirror segments were finished by a combination of ultrahigh precision cutting and mechanical polishing techniques to realize both an extremely smooth surface and fine figure accuracy. The neutron focusing performance was evaluated using the BL06 beam line at J-PARC/MLF and compared with a non-segmented mirror. It was confirmed that the multiple segment design doesn't affect the focusing performance for of a millimeter sized focused beam. The manufacture method is promising to fabricate an ellipsoidal mirror with high enough performance for a compact focusing SANS instrument.

Design of multi-shell nested fully annular quasi-ellipsoidal focusing mirrors for small-angle neutron scattering

“…Among reflected focusing optics, Kirkpatrick-Baez (Ice et al, 2005(Ice et al, , 2006 and Montel (Ice et al, 2009) mirrors have a small geometric collecting area of the order of a square millimetre in the azimuth. Fully annular ellipsoidal and Wolter mirrors have a structural advantage that significantly enhances the neutron flux by tens of times or even more (Khaykovich et al, 2011;Mildner & Gubarev, 2011;Takeda et al, 2018;Hussey et al, 2021). Ellipsoidal mirrors have a higher reflection efficiency due to their single reflections, while Wolter mirrors can achieve a shorter focusing distance and eliminate the severe coma of ellipsoidal mirrors.…”