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The Parallel Beam Diffractometer (PBD) Laboratory

Picture of PBD set up for wavelength measurement

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 640f, and measurements of the spectra of various important X-ray anode materials.  

A new project being developed is a robotic sample changer which will allow us to individually certify SRMs for which this is important.  The first application will be a more precise certification of SRM 2000, a single-crystal silicon substrate with a SiGe overlayer.



Created September 6, 2016, Updated August 5, 2020