NEW SOFT-ENERGY X-RAY ABSORPTION SPECTROSCOPY INSTRUMENT

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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 instrument for XAS measurements in the 2-5 keV range was commissioned in 2007 and during 2008 a further enhanced setup was constructed and implemented for BL4-3. In this energy range, x-rays have a very short path length in air and thus the entire beam path is enclosed in a helium atmosphere to enable data collection. These setups incorporate several features to improve efficiency and ease of use. This includes computer-controlled motorized x-ray slits, a motorized linear motion feed-through, and a computer-controlled shutter to close off the beam between data points (to reduce x-ray induced damage to samples). Oxygen sensors and flowmeters are utilized for monitoring the purity of the helium atmosphere. A LHe cryostream is now in routine use for cooling samples to ~50 K. Modifications of the cooling setup are planned to improve ease of use and allow for better thermal isolation of the detector.