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Title: Innovative diffraction gratings for high-resolution resonant inelastic soft x-ray scattering spectroscopy

Abstract

High-resolution Resonant Inelastic X-ray Scattering (RIXS) requires diffraction gratings with very exacting characteristics. The gratings should provide both very high dispersion and high efficiency which are conflicting requirements and extremely challenging to satisfy in the soft x-ray region for a traditional grazing incidence geometry. To achieve high dispersion one should increase the groove density of a grating; this however results in a diffraction angle beyond the critical angle range and results in drastic efficiency loss. The problem can be solved by use of multilayer coated blazed gratings (MBG). In this work we have investigated the diffraction characteristics of MBGs via numerical simulations and have developed a procedure for optimization of grating design for a multiplexed high resolution imaging spectrometer for RIXS spectroscopy to be built in sector 6 at the Advanced Light Source (ALS). We found that highest diffraction efficiency can be achieved for gratings optimized for 4{sup th} or 5{sup th} order operation. Fabrication of such gratings is an extremely challenging technological problem. We present a first experimental prototype of these gratings and report its performance. High order and high line density gratings have the potential to be a revolutionary new optical element that should have great impact inmore » the area of soft x-ray RIXS.« less

Authors:
; ; ; ;  [1]
  1. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States)
Publication Date:
OSTI Identifier:
22608400
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1741; Journal Issue: 1; Conference: SRI2015: 12. international conference on synchrotron radiation instrumentation, New York, NY (United States), 6-10 Jul 2015; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; ADVANCED LIGHT SOURCE; COMPUTERIZED SIMULATION; DESIGN; DIFFRACTION GRATINGS; DISPERSIONS; EFFICIENCY; LAYERS; OPTIMIZATION; RESOLUTION; SOFT X RADIATION; SPECTROMETERS; SPECTROSCOPY; X-RAY DIFFRACTION

Citation Formats

Voronov, D.L., Warwick, T., Gullikson, E. M., Salmassi, F., and Padmore, H. A. Innovative diffraction gratings for high-resolution resonant inelastic soft x-ray scattering spectroscopy. United States: N. p., 2016. Web. doi:10.1063/1.4952887.
Voronov, D.L., Warwick, T., Gullikson, E. M., Salmassi, F., & Padmore, H. A. Innovative diffraction gratings for high-resolution resonant inelastic soft x-ray scattering spectroscopy. United States. doi:10.1063/1.4952887.
Voronov, D.L., Warwick, T., Gullikson, E. M., Salmassi, F., and Padmore, H. A. 2016. "Innovative diffraction gratings for high-resolution resonant inelastic soft x-ray scattering spectroscopy". United States. doi:10.1063/1.4952887.
@article{osti_22608400,
title = {Innovative diffraction gratings for high-resolution resonant inelastic soft x-ray scattering spectroscopy},
author = {Voronov, D.L. and Warwick, T. and Gullikson, E. M. and Salmassi, F. and Padmore, H. A.},
abstractNote = {High-resolution Resonant Inelastic X-ray Scattering (RIXS) requires diffraction gratings with very exacting characteristics. The gratings should provide both very high dispersion and high efficiency which are conflicting requirements and extremely challenging to satisfy in the soft x-ray region for a traditional grazing incidence geometry. To achieve high dispersion one should increase the groove density of a grating; this however results in a diffraction angle beyond the critical angle range and results in drastic efficiency loss. The problem can be solved by use of multilayer coated blazed gratings (MBG). In this work we have investigated the diffraction characteristics of MBGs via numerical simulations and have developed a procedure for optimization of grating design for a multiplexed high resolution imaging spectrometer for RIXS spectroscopy to be built in sector 6 at the Advanced Light Source (ALS). We found that highest diffraction efficiency can be achieved for gratings optimized for 4{sup th} or 5{sup th} order operation. Fabrication of such gratings is an extremely challenging technological problem. We present a first experimental prototype of these gratings and report its performance. High order and high line density gratings have the potential to be a revolutionary new optical element that should have great impact in the area of soft x-ray RIXS.},
doi = {10.1063/1.4952887},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1741,
place = {United States},
year = 2016,
month = 7
}
  • A grand challenge in soft x-ray spectroscopy is to drive the resolving power of monochromators and spectrometers from the 10 4 achieved routinely today to well above 10 5. This need is driven mainly by the requirements of a new technique that is set to have enormous impact in condensed matter physics, Resonant Inelastic X-ray Scattering (RIXS). Unlike x-ray absorption spectroscopy, RIXS is not limited by an energy resolution dictated by the core-hole lifetime in the excitation process. Using much higher resolving power than used for normal x-ray absorption spectroscopy enables access to the energy scale of soft excitations inmore » matter. These excitations such as magnons and phonons drive the collective phenomena seen in correlated electronic materials such as high temperature superconductors. RIXS opens a new path to study these excitations at a level of detail not formerly possible. However, as the process involves resonant excitation at an energy of around 1 keV, and the energy scale of the excitations one would like to see are at the meV level, to fully utilize the technique requires the development of monochromators and spectrometers with one to two orders of magnitude higher energy resolution than has been conventionally possible. Here we investigate the detailed diffraction characteristics of multilayer blazed gratings. These elements offer potentially revolutionary performance as the dispersive element in ultra-high resolution x-ray spectroscopy. In doing so, we have established a roadmap for the complete optimization of the grating design. Traditionally 1st order gratings are used in the soft x-ray region, but we show that as in the optical domain, one can work in very high spectral orders and thus dramatically improve resolution without significant loss in efficiency.« less
  • Photon-excited B {ital K} fluorescence spectra were measured for hexagonal boron nitride using tunable synchrotron radiation below and above the B {ital K} edge. We report Raman-like resonant inelastic scattering of soft x rays involving excitation of delocalized valence-band electrons. The inelastic scattering features track with the excitation energy below threshold, go through a resonance as the excitation is tuned to the B(1{ital s}) core-exciton energy, and evolve into incoherent fluorescence as the excitation is raised further. The energy loss is identified as equivalent to an electronic transition of valence {sigma} electrons to {pi}{sup *} conduction-band states. {copyright} {ital 1996more » The American Physical Society.}« less
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