DEVELOPMENT OF MULTILAYER SUPERMIRROR COATINGS FOR NEUTRON GUIDETUBES

AT MANY NATIONAL LABORATORIES, IT IS HIGHLY DESIRABLE TO IMPROVE THE USE AND EFFICIENCY OF NEUTRON REACTOR FACILITIES. SEVERAL LABORATORIES HAVE PROPOSED IMPROVING THE QUALITY AND QUANTITY OF EXPERIMENTATION BY CHANNELING NEUTRONS TO REMOTE EXPERIMENTAL STATIONS VIA GUIDETUBES. THE ADVANTAGES OF THESE GUIDETUBE FACILITIES HAVE BEEN DEMONSTRATED IN EUROPE AND JAPAN. A MULTI-LAYERED THIN FILMCOATING, KNOWN AS A "SUPERMIRROR", CAN REPLACE NI COATINGS FOR SIGNIFICANTLY IMPROVED GUIDETUBE EFFICIENCY. FOR THE PAST DECADE, THERE HAS BEEN A GLOBAL RESEARCH EFFORT TO PRODUCE USEFUL GUIDETUBE SUPERMIRRORS. USE OF STANDARD VACUUM DEPOSITION TECHNIQUES HAS NOT BEEN SUCCESSFUL, APPARENTLY BECAUSE OF LAYER INSTABILITIES THAT ARE MATERIAL,SYSTEM, AND PROCESS RELATED. TO PRODUCE RELIABLE SUPERMIRROR PRODUCTS ON A LARGE SCALE, PROBLEMS OF CONTROLLING LAYER GROWTH MUST BE ADDRESSED. PROBLEMS THAT AFFECT LAYER UNIFORMITY INCLUDE CRYSTAL GROWTH, STRESS/STRAIN EFFECTS, AND FILM/SUBSTRATE ADHESION. PHASE IWILL USE STATE-OF-THE-ART DEPOSITION PROCESS TECHNIQUES TO INVESTIGATE METHODS FOR CONTROLLING THE LAYER DISTURBANCES ON SUBSTRATES OF A LIMITED SIZE. EACH METHOD WILL BE EVALUATED FOR ITS SUCCESS IN IMPROVING LAYERING QUALITY AND NEUTRON REFLECTIVITY. IN PHASE II, THE PREFERRED PROCESS WILL BE INVESTIGATED FOR OPTIMIZATION OF LARGE SCALE LAYER UNIFORMITY, YIELDS, AND DIFFERENT METHODS OF BATCH PROCESSING. THIS WILL BE THE BASIS FOR A PROPOSED BUSINESS PLAN IN PHASE III.