SI Crystals

Brand Name or Equal Crystal Scientific Ltd. Qty 4 LCLS LODCM Si-111 and Si-220 Crystals Special instructions for cutting and polishing of crystals: Si-111 and Si-220 single crystals needed for LUSI instruments, XCS and XPP monochromators. Quantity: Four in total. Break down: Two (2) in Silicon-111 and Two (2) in Silicon-220. Pair of crystals (two Si-111 or two Si-220) must be from same ingot. Crystals must be free of strain after polishing and etching. Final polishing requirement on diffracting crystal surfaces -- the surfaces facing the beam. But all surfaces should be free of machine damage and strain. The vendor will have to etch all surfaces for removing strain. All surfaces lapped to removed machining damage, all surfaces etched to remove any induced strain. Specifications for roughness/flatness: RMS surface roughness: 0.3 nm or better Optical flatness: Quarter lambda (at 638 nm) or better. Quarter lambda or better, peak to valley, is a minimum requirement. RMS numbers will be preferred for better understanding of surface flatness. A Strehl ratio number of 0.82 or better is a good equivalent, taking into account RMS deviations. A comparable number will work. Orientation accuracy (w.r.t crystalline axis of crystal): +/- 0.01 degree, with quoted extra cost to deliver this accuracy. Or best effort. (Definitely less than 0.05 degree). Vendor to specify instrumentation used to inspect measurements