Papers by Author: H.M. Shimizu

Abstract: 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.

Abstract: In order to improve the application of neutron scattering technique, a new neutron optical device, which optical system consists of an array of several ten neutron Fresnel lenses, is designed by the researcher engaging in the study of neutron optics. Neutron Fresnel lenses for this new device have the same symmetric concave form. Its center is a spherical surface and the other surfaces are conic section. MgF2 single crystal glass is selected as the material for making neutron Fresnel lens because of its high transparence. Considering the form complicity and the brittle properties of MgF2 material, the fabrication of neutron Fresnel lens is of very difficulty. Form ELID (electrolytic in-process dressing) grinding was used for grinding the neutron Fresnel lens in this first study. The optima of grinding conditions for #325, #1200 and #4000 cobalt bonding diamond abrasive wheels are obtained through a series of tests. The MgF2 material is removed at the ductile mode by using #4000 abrasive wheel. Thus, the neutron Fresnel lens fabricated has low roughness and high transparence. The transmission of an array of 50 pieces of neutron Fresnel lens is 92.5 percents to neutron beam with wavelength 5Å and 79.3 percents to 16Å.