Synchrotron powder X-ray diffractometer beamline at J. Bennett Johnston, Sr., Center for Advanced Microstructures and Devices

Abstract

The J. Bennett Johnston, Sr., Center for Advanced Microstructures and Devices (CAMD) is a synchrotron ring operating at 1.3 GeV, with the ring current typically ranging from 230 to 100 mA. An X-ray powder diffraction beamline was recently commissioned at CAMD at the bending magnet port 7A. The powder diffraction beamline consists of a Brazilian-designed double crystal monochromator, a Huber four-circle diffractometer, and a Canberra germanium solid-state detector. The monochromator is equipped with Si 111 and Ge 220 crystals. The Canberra high purity germanium solid-state detector has a resolution of 130 eV at Mn K α. For typical use, the diffractometer circle is set to 17 cm, and the source and receiving slits have been set to 300 and 200 μm, respectively. A sample spinner is used for improved particle size averaging. Wavelength can be shifted in a matter of minutes. Preliminary runs of NIST standards, for example, lanthanum hexaboride (LaB 6) (SRM 660a), show good performance over a wide two-theta range. Rietveld refinement of novaculite (SiO 2) shows lower residual error for the same mineral compared to that obtained from a run with a conventional X-ray source. At the beamline, the user can use MDI's Jade version 7.5 software. The user also has access to International Center for Diffraction Data's Powder Diffraction File-2 database consisting of more than 163,000 inorganic entries and International Crystal Structure Data's crystal structure database with more than 93,000 entries.