CAPILLARY-OPTICS DEVELOPMENT FOR HIGH FLUX X-RAY MAPPING & SPECTROSCOPY

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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 pre-focused x-ray beam at 12 keV and 9 keV was used to illuminate a single-bounce capillary (SBC) to generate a high flux x-ray microbeam. The BioCAT undulator x-ray beam of 1.18¿1013 ph/s was pre-focused using a sagittal focusing double crystal monochomator and a bimorph mirror (195 ¿m x 125 ¿m, FWHM horizontal and vertical respectively). The capillary entrance was aligned with the pre-focused beam focal point, thus the full undulator beam was illuminating the capillary walls. Two alignment configurations were tested: a) the center of the capillary aligned with the pre-focused beam (in line) and b) one side of the capillary aligned with the beam (off line). The latter being the better in terms of flux delivered and smaller spot size (d 10 microns FWHM in both directions). A 3.3¿1012 ph/s delivered flux was measured. The photon flux density was 4.2¿1010 ph/s/um2. The combination of the beamline main optics with a large working distance (approximately 20 mm) capillary used in this experiment, make it suitable for many microprobe fluorescence applications that require micron size x-ray beam and high flux density. These features are extremely convenient for biological samples, where typical metal concentrations are in the range of a few ng/cm2. Micro-XANES experiments are also feasible using this combined optical arrangement.