Study of a nested neutron-focusing supermirror system for small-angle neutron scattering

Neutron current is crucial for neutron scattering measurements, especially for those at compact sources. Among various neutron optical devices, neutron-focusing mirrors have been drawing increasing attention due to their great potential in enhancing neutron current on sample for small-angle neutron scattering instruments. The state-of-the-art neutron-focusing mirrors, which can collect a large divergence of neutron beam, are required to be nestable and simultaneously be able to be coated with supermirrors. In this paper, we employ the nested conical optics to manufacture nested neutron-focusing mirrors with supermirror coatings. This technique enables such mirrors by assembling partial cylindrical glass segments into nested shells. A prototype system, containing two shell conical mirrors with m=2 Ni/Ti supermirror coatings, has been designed and manufactured. Ray-tracing simulations and neutron beam experiments have been carried out to evaluate its focusing performance and neutron reflectivity. The results show that neutron current collected by this prototype system is about 26 times higher than that by a pinhole design with the same Q(min). Moreover, we discuss some possible further improvements on the fabrication process.