The Ultrahigh Resolution IXS Beamline of NSLS-II: Recent Advances and Scientific Opportunities

Abstract

The ultrahigh resolution IXS beamline of NSLS-II is designed to probe a region of dynamic response that requires an ultrahigh energy and momentum resolution of up to 0.1 meV and < 0.1 nm-1 , respectively, which is currently still beyond the reach of existing low and high frequency inelastic scattering probes. Recent advances at NSLS-II in developing the required x-ray optics and instrumentation based on the use of extremely asymmetric Bragg back reflections of Si have allowed us to achieve sub-meV energy resolution with sharp tails and high efficiency at a medium energy of around 9.1 keV, thereby validating the optical design of the beamline for the baseline scope and paving the way for further development towards the ultimate goal of 0.1 meV. The IXS beamline is expected to provide a broad range of scientific opportunities, particularly in areas of liquid, disordered and bio-molecular systems.

The Spectrum of Density Fluctuations of Noble Gases Probed by THz Neutron and X-ray Spectroscopy

“…This will enable to perform IXS experiments with a resolution function <1 meV broad and essentially Gaussian in shape. The feasibility of such high resolution optical schemes has been demonstrated in a recent work [118], while a beamline based on this working principle has recently become operative at the new synchrotron NSLS II of Brookhaven National Laboratory [119]. This new opportunity is certainly quite encouraging and, in the near future, deemed to further advance our knowledge of the complex THz dynamics of simple liquids.…”

Compact pseudo-2D strip detector system for sub-meV IXS

“…After the D crystal reflection, beam passes through the C crystal via anomalous transmission and is restored to its original size by the W crystal before finally striking the detector. This arrangement is designed to produce 0.7 meV bandwidth [1]. The detector's energy resolution therefore is less critical than its geometry and thresholding features.…”

“…Utilizing in-house capabilities for mechanical and electronics fabrication, a custom multi-pixel sensor system was undertaken to support the IXS beamline of NSLS-II [1] which makes use of a novel grazing-incidence backscatter scheme to achieve sub-meV resolution at 9.13 keV photon energy [2]. With first light anticipated in 2014, a rapid and low-cost detector development was pursued, providing the unique capabilities needed utilizing established detector capabilities at BNL [3].…”

X-ray-photon scattering by an excited atom

“…The time scale for electron-electron electromagnetic interaction is characterized by the quantity l/c ≈ 0.2 as for the Bohr radius l ≈ 5.29 × 10 −11 m. Accounting for these effects leads to modifications of integrals in (8), (9), (13), and (14). For example, for the integral in (8) we have…”