Fine ELID Grinding on the Symmetric Paraboloidal Mirror of Quartz

Quartz has excellent optical properties and thus it is often used as the material of mirror and lens. However, it is almost impossible to be machined by cutting due to its brittle and high hardness. Grinding is a common method for machining quartz. One of the authors designed a new type of a paraboloidal mirror of quartz for the neutron optical devices. The fabrication process of this mirror was investigated in this experiment. A jig with two grooves of 90 degrees was made and two workpieces were stuck on the jig using the wax melt at about 60 degrees centigrade. The two workpieces were first ground applying ELID (electrolytic in-process dressing) grinding method with #325 and #1200 cast iron bonding diamond abrasive wheels. Then the ground surface was polished with CeO2 slurry. The finished surface roughness was Ra2.0nm and rms2.4nm and its form error about 2μm. After coating process, its properties of focusing neutron beam were measured. The results were that the reflecting rate was 42%, gain 1.9 and 2.3mm×10.1mm beam focused to 1.6mm×2.1mm.