DEVELOPMENT AND COMMISSIONING OF MICROBEAM CAPABILITIES ON BL12-2

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Microbeam mode for studying microcrystals is being developed and implemented. A precision microdiffractometer was developed in-house and installed. The system is based on a single rotation axis high-precision air bearing and incorporates 3 degrees of motion for sample alignment with 1 micron reproducibility and 1.4 micron sphere of confusion (SOC). The system has been thermally stabilized with a protective copper heat shield incorporated in the body of the diffractometer. The experimental table has been thermally compensated and the hutch temperature is controlled to +/- 0.5 degrees. An in-line camera was incorporated into the beam line for viewing microcrystals along the beam axis, which reduces misalignments due to parallax. The camera can resolve 1 micron features and incorporates 3 degrees of motion for easy alignment and a zoom feature (8x). A pop-in screen has been included which provides backlight for the small samples and a fluorescent screen for identifying the beam position relative to the sample. The camera has been incorporated into the Blu-Ice control system and is compatible with remote access, etc. A prototype automated collimation system was recently tested. The system allows the automatic selection of small beam sizes (smaller than the native focus of 55 um x 20 um). The tiny collimators are held in place on small plastic strips just in front of the in-line camera lens. However these strips do not distort the in-line image to any significant extent. A new system is being fabricated that will allow the selection of 4 beam sizes ranging from 5-20 microns.