ELID Grinding of a Symmetric Paraboloidal Quartz Mirror(Nanoprecision Elid grinding)

Abstract

The designed form and surface quality of focusing neutron mirror is a main factor affecting the performance of the neutron optical devices. In order to improve the situation, one of the authors designed a new type of mirror for focusing neutron beams. Its form is an inside deep rotary paraboloid and the material used is quartz. To test the optical performances of the designed parameters and simplify the fabrication process, the first fabrication was to grind the 1/4 of the mirror, cut along the symmetric axis by two perpendicular planes, thus the surface to be ground is an outside symmetric paraboloid. The fabrication process was investigated in this experiment. The workpiece was first ground applying the ELID method with #325 and #1200 cast iron bonding diamond abrasive wheels. Then the ground surface was polished with CeO_2 slurry. The finished surface roughness was Ra2.0nm and rms2.4nm and the form error was about 2μm. After a coating process, its properties of focusing neutron beams were investigated. The optical properties obtained included a reflecting rate of 42%, gain 1.9 and 2.3mm×10.1mm beam focused to 1.6mm×2.1mm.