Calculations on ellipsoidal and conical focusing mirrors for small angle neutron scattering

Various geometries of neutron focusing mirrors have been proposed to increase the neutron flux since the existing neutron sources have a much lower brilliance than synchrotron X-ray sources, especially the compact neutron sources. We applied the ellipsoidal mirrors to the design of Small Angle Neutron Scattering (SANS) instruments at Compact Pulsed Hadron Source of Tsinghua University and a lot of ray-tracing simulations have been carried out to optimize the geometry and analyzed the relationships between the performances of SANS instruments and geometrical parameters of nested ellipsoidal mirrors. Ellipsoid-shaped conical mirror was proposed to overcome the difficulty of fabricating highly aspherical mirrors, such mirrors are easier to fabricate and to be nested. The aberration of the ellipsoid-shaped conical mirror was analyzed and evaluated.