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X-RAY RUNS: Apply for Beamtime

2017  May 17 - June 29

2017  October 11 - December 21
2017  Proposal deadline: 08/01/17
2017  BTR deadline: 09/10/17

CHESS scientist Ken Finkelstein and engineers Aaron Lyndaker and Tom Krawczyk have just completed a unique, high resolution spectrometer for x-ray fluorescence studies. The system was developed in close collaboration with user groups using our XES capability over the last 5 years. The spectrometer name, DAVES, is both an acronym and tribute in memory of a good friend to the x-ray community, Dave Rognlie, who supplied HUBER diffraction equipment in the USA for over 30 years. DAVES – Dual Array Valence Emission Spectrometer - uses the simplest design possible for a multiple-crystal-analyzer, Rowland circle spectrometer, with simultaneous capability for independent measurements of two emission lines from one sample. Each Rowland circle consists of a HUBER Θ-2Θ rotation stage with independent vertical/horizontal translation as illustrated in Figure 1. Up to 5 crystal can collect each emission spectrum.

Figure 1

Figure 1: X-ray emission spectrometer DAVES uses independent control of arrays of spherical analyzer crystals, and detectors (not shown) for simultaneous collecting spectra from a sample (represented by red dot on the symmetry plane) with more than one active emission site. The incident x-ray beam is represented by a black arrow.

The 2-color collection capability was included because nature has evolved many proteins utilizing more than one metal active site to effect difficult chemical reactions. These include the class Ic ribonucleotide reductase (RNR) using Mn/Fe to produce building blocks of DNA, hydrogenases (Ni/Fe), nitrogenases (V/Fe), and photosystem II (Mn/Ca). The new design also enables a doubling in signal collection capability, improved geometry for helium flight paths, enhanced flexibility in designing new experiments, and optimizing data collection methods. We plan to present the design and first results at 12th International SRI Conference to be held in NYC in July 2015.



Submitted by: Ken Finkelstein, CHESS, Cornell University