Abstract
Neutron beam is a useful probe for material analysis and non-destructive testing since it has unique advantages such as deep penetration into materials, sensitive to light elements and capable of measuring magnetic properties. Compared with X-ray beams from synchrotron radiation or free electron laser, the brilliance of neutron beam is small so there are a number of plans to construct neutron instrumens using focusing mirror with higher intensity and smaller spot size. In this paper, for the first time, we propose an ellipsoidal structure mirror by using a metal substrate to focus neutron beams. As the metal substrate, electroless nickel is adopted because of its amorphous structure, machinability and relatively large critical angle for neutrons. Compared with mirror made by glass substrate, it is easy to be fabricated and the manufacturing time can be greatly saved. Besides, it has a good mechanical handling property. The mirror is designed by considering the critical angle of neutron beam. Then a test piece of ellipsoidal neutron mirror is fabricated by combining ultrahigh precision cutting and smooth polishing process, and the form accuracy of 5 μm P-V with surface roughness of 0.7 nm rms is obtained. The total manufacturing time is only one week. Test results using neutron beam will be mentioned. Through this experimental manufacturing, the feasibility of the proposed method is verified.
