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The Parallel Beam Diffractometer (PBD) Laboratory
This is a view of the entire PBD sitting on its granite optical table. It is configured for double-crystal measurements of X-ray wavelengths.
The Parallel Beam Diffractometer laboratory is a highly-controlled space (0.01 degree C stability) containing a set of absolutely calibrated stacked goniometer stages which are the platform for precision measurement of diffraction angles. It is used to establish lattice constants of SRM powders, and to measure X-ray wavelengths with unprecedented accuracy, in a way directly traceable to the SI definition of the second. In the past few years, the instrument has been brought into full operation, with publications describing its angular calibration and alignment (compensation of short-period errors, long-period errors and alignment). Current projects underway for it include new measurements of lattice spacings of NIST SRMS 660c and 640d, and measurements of the copper Kα complex line shape.