MICRODIFFRACTION DEVELOPMENT

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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. A new development over the last year is the use of our K-B mirror system for micro-diffraction applications. This approach allows collection of a large fraction of the available beam and offers great flexibility in adjusting beamsize and divergence for specific needs. Functional beam size ranges from about 2 x 3 microns to approximately 10x10 microns. This allows collection of high quality diffraction from very small sample volumes minimizing the diffuse scatter collected by irradiating non-crystalline / poorly aligned parts of the sample. Considerable progress has been made in determining the operational parameters for both high resolution, low divergence that are optimal for connective tissue applications and high flux, larger divergence applications which can be useful for studies of such things as amyloid deposits in tissues. A new set of small apertures was implemented in front of the sample holder to block unwanted parasitic x-rays coming from the KB mirrors system. The apertures (~ 20 micron diameter) are mounted on an XY positioner driven by high precision Newport MFN stages. These apertures allowed us to optimize the signal to background ratio by reducing some parasitic scattering originated by the KB mirrors. A new inline sample alignment system was also tested during this period. The system allows the visualization of the sample during the alignment procedure without removing the CCD detector from the beam path. These developments have informed the design of a dedicated micro-diffraction setup for the front of the hutch at BioCAT to be implemented in the upcoming grant cycle.