GRAPHITE MONOCHROMATOR CRYSTAL WITH LOW MOSAIC SPREAD

GRAPHITE MONOCHROMATOR CRYSTALS ARE COMMONLY USED IN X-RAY DIFFRACTION WORK, BECAUSE THEY HAVE HIGH EFFICIENCY AND USEFUL MOSAIC STRUCTURE CHARACTERISTICS. COMMERCIALLY AVAILABLE GRAPHITE CRYSTALS PRODUCED BY HIGH TEMPERATURE PYROLYSIS HAVE MOSAIC SPREAD ~0.5 DEGREES. HIGH RESOLUTION DIFFRACTION STUDIES, THE USEFUL X-RAY INTENSITY ON THE SAMPLE CAN BE INCREASE SEVERALFOLD BY REDUCING THE MOSAIC SPREAD ACCORDINGLY. PROTEIN CRYSTALLOGRAPHY WOULD BENEFIT FROM CRYSTALS WITH MOSAIC SPREAD AS LOW AS 0.05 DEGREES. VAPOR DEPOSITION OF GRAPHITE FIBER AT LOWER TEMPERATURES PRODUCES LAMINAR MICROSTRUCTIVE WITH GREATER ORDERING THAN THAT OBTAINED IN HIGH TEMPERATURE PYROLYSIS. THE SLOWER DEPOSITION RATE AT LOWER TEMPERATURES WOULD BE ADEQUATE FOR THIN CRYSTALS NEEDED IN X-RAY APPLICATIONS. THIS PROJECT WILL INVESTIGATE PLANAR GRAPHITE CRYSTALS DEPOSITED UNDER LOWW TEMPERATURE CONDITIONS THAT MAY THEN BE ANNEALED AT HIGH TEMPERATURES TO ACHIEVE LOW MOSAIC SPREAD. PHASE I EFFORT WILL INVESTIGATE PROCESSING AND ASSESS THE FEASIBLITY OF PRODUCING PLANAR AND CURVED GRAPHITE CRYSTALS WITH LOW MOSAIC SPREAD. PHASE II OF THIS PROJECT WOULD FURTHER DEVELOP PROCESSING METHODS AND FABRICATE MONOCHROMATOR CYRSTALS WITH SPREAD <0.5 DEGREES.