ION BEAM POLISHING OF SINGLE CRYSTALS, POLYCRYSTALLINE SOLIDS AND THIN FILMS FOR GRAZING INCIDENCE MIRRORS.

THE COLLECTION AND FOCUSSING OF X RAYS AND VACUUM ULTRAVIOLET LIGHT (VUV) FROM THE SUN AND OTHER BODIES IN OURSOLAR SYSTEM REQUIRES GRAZING INCIDENCE MIRRORS WITH EXCELLENT SURFACE FIGURES, LOW SCATTER, LOW SURFACE ROUGHNESS AND ACCURATE FOCAL LENGTHS. THE MANUFACTURE OF ASPHERIC MIRRORS WITH THE REQUIRED HIGH PERFECTION IS BOTH COSTLY AND DIFFICULT WITH CURRENTLY AVAILABLE MANUFACTURING TECHNIQUES. ION BEAM POLISHING HAS RECENTLY BEEN SHOWN TO BE CAPABLE OF PRODUCING HIGH QUALITY SURFACES, ON MATERIAL LIKE FUSED SILICA AND ZERODUR, BUT THERE IS INADEQUATE INFORMATION ON WHAT OTHER MATERIALS CAN BE SUCCESSFULLY POLISHED WITH ION BEAMS. WE PROPOSE TO STUDY THE ION BEAM POLISHING OF A SELECTED GROUP OF MATERIALS THAT HAVE HIGH POTENTIAL FOR USE AS X-RAY MIRRORS. THIS GROUP CONSISTS OF MOLYBDENUM, SILICON AND SILICON CARBIDE IN THE FORM OF SINGLE CRYSTALS, POLYCRYSTALLINE SOLIDS AND CVD DEPOSITED FILMS. FOR EACH MATERIAL WE PROPOSE TO ESTABLISH WHICH MATERIALS CAN BE ION BEAM POLISHED TO THE REQUISITE FIGURE AND SURFACE ROUGHNESS AND ALSO TO DETERMINE A MEASURE OF THE INITIAL SURFACE ROUGHNESS THAT IS REQUIRED FOR ION BEAM POLISHING TO ACHIEVE AN ACCEPTABLE FINAL SURFACE. THE SURFACE FLATNESS, SURFACE ROUGHNESS AND SUBSURFACE DAMAGE AND OF ALL SAMPLES WILL BE MEASURED.