Use of diamond turned mirrors for synchrotron radiation

The diamond turning technique has great interest for users of synchrotron radiation because of its ability to produce surfaces of arbitrary shape. It also has the advantage of being well adapted to producing metal optics. These are of interest because they lend themselves to water cooling and hence represent one approach to the proplem of high synchrotron radiation power loadings on optical surfaces. The optical figure produced by diamond turning is generally adequate for synchrotron radiation applications. The main difficulty centers around the question of smoothness. Diamond turned surfaces must receive a final polish after machining before they are sufficiently smooth for use with ultra-violet or X-ray radiation. The manufacturing stages can be carried out by various groups in the optics industry and the National Synchrotron Light Source has procured a considerable number of mirrors and is having them polished for use on the VUV storage ring. At the time of writing one mirror has been completed and evaluated and we give the results for this and discuss the indications for the future. The important measurement of the r.m.s. height of the surface roughness has given a value of (3.4+-0.9) A using total integrated scattter of visible light at normal incidence. (orig.)