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Title: Circular dichroism measurements at an x-ray free-electron laser with polarization control

Abstract

A non-destructive diagnostic method for the characterization of circularly polarized, ultraintense, short wavelength free-electron laser (FEL) light is presented. The recently installed Delta undulator at the LCLS (Linac Coherent Light Source) at SLAC National Accelerator Laboratory (USA) was used as showcase for this diagnostic scheme. By applying a combined two-color, multi-photon experiment with polarization control, the degree of circular polarization of the Delta undulator has been determined. Towards this goal, an oriented electronic state in the continuum was created by non-resonant ionization of the O{sub 2} 1s core shell with circularly polarized FEL pulses at hν ≃ 700 eV. An also circularly polarized, highly intense UV laser pulse with hν ≃ 3.1 eV was temporally and spatially overlapped, causing the photoelectrons to redistribute into so-called sidebands that are energetically separated by the photon energy of the UV laser. By determining the circular dichroism of these redistributed electrons using angle resolving electron spectroscopy and modeling the results with the strong-field approximation, this scheme allows to unambiguously determine the absolute degree of circular polarization of any pulsed, ultraintense XUV or X-ray laser source.

Authors:
; ; ;  [1];  [2];  [3]; ; ; ; ; ; ; ; ; ; ;  [4]; ; ;  [5] more »; « less
  1. Deutsches Elektronen-Synchrotron, Notkestraße 85, 22607 Hamburg (Germany)
  2. PULSE at Stanford, 2575 Sand Hill Road, Menlo Park, California 94025 (United States)
  3. Institut für Physik, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel (Germany)
  4. SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States)
  5. European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg (Germany)
Publication Date:
OSTI Identifier:
22597648
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 87; Journal Issue: 8; 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; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; APPROXIMATIONS; COMPUTERIZED SIMULATION; DIAGNOSTIC TECHNIQUES; DICHROISM; ELECTRON SPECTROSCOPY; ELECTRONS; EXTREME ULTRAVIOLET RADIATION; FERMILAB ACCELERATOR; FREE ELECTRON LASERS; IONIZATION; LINEAR ACCELERATORS; MULTI-PHOTON PROCESSES; PHOTONS; POLARIZATION; PULSES; STANFORD LINEAR ACCELERATOR CENTER; WAVELENGTHS; WIGGLER MAGNETS; X RADIATION; X-RAY LASERS

Citation Formats

Hartmann, G., Shevchuk, I., Walter, P., Viefhaus, J., Lindahl, A. O., Knie, A., Hartmann, N., Lutman, A. A., MacArthur, J. P., Glownia, J. M., Helml, W., Huang, Z., Marinelli, A., Nuhn, H.-D., Moeller, S., Coffee, R. N., Ilchen, M., E-mail: markus.ilchen@xfel.eu, Buck, J., Galler, A., Liu, J., and and others. Circular dichroism measurements at an x-ray free-electron laser with polarization control. United States: N. p., 2016. Web. doi:10.1063/1.4961470.
Hartmann, G., Shevchuk, I., Walter, P., Viefhaus, J., Lindahl, A. O., Knie, A., Hartmann, N., Lutman, A. A., MacArthur, J. P., Glownia, J. M., Helml, W., Huang, Z., Marinelli, A., Nuhn, H.-D., Moeller, S., Coffee, R. N., Ilchen, M., E-mail: markus.ilchen@xfel.eu, Buck, J., Galler, A., Liu, J., & and others. Circular dichroism measurements at an x-ray free-electron laser with polarization control. United States. doi:10.1063/1.4961470.
Hartmann, G., Shevchuk, I., Walter, P., Viefhaus, J., Lindahl, A. O., Knie, A., Hartmann, N., Lutman, A. A., MacArthur, J. P., Glownia, J. M., Helml, W., Huang, Z., Marinelli, A., Nuhn, H.-D., Moeller, S., Coffee, R. N., Ilchen, M., E-mail: markus.ilchen@xfel.eu, Buck, J., Galler, A., Liu, J., and and others. 2016. "Circular dichroism measurements at an x-ray free-electron laser with polarization control". United States. doi:10.1063/1.4961470.
@article{osti_22597648,
title = {Circular dichroism measurements at an x-ray free-electron laser with polarization control},
author = {Hartmann, G. and Shevchuk, I. and Walter, P. and Viefhaus, J. and Lindahl, A. O. and Knie, A. and Hartmann, N. and Lutman, A. A. and MacArthur, J. P. and Glownia, J. M. and Helml, W. and Huang, Z. and Marinelli, A. and Nuhn, H.-D. and Moeller, S. and Coffee, R. N. and Ilchen, M., E-mail: markus.ilchen@xfel.eu and Buck, J. and Galler, A. and Liu, J. and and others},
abstractNote = {A non-destructive diagnostic method for the characterization of circularly polarized, ultraintense, short wavelength free-electron laser (FEL) light is presented. The recently installed Delta undulator at the LCLS (Linac Coherent Light Source) at SLAC National Accelerator Laboratory (USA) was used as showcase for this diagnostic scheme. By applying a combined two-color, multi-photon experiment with polarization control, the degree of circular polarization of the Delta undulator has been determined. Towards this goal, an oriented electronic state in the continuum was created by non-resonant ionization of the O{sub 2} 1s core shell with circularly polarized FEL pulses at hν ≃ 700 eV. An also circularly polarized, highly intense UV laser pulse with hν ≃ 3.1 eV was temporally and spatially overlapped, causing the photoelectrons to redistribute into so-called sidebands that are energetically separated by the photon energy of the UV laser. By determining the circular dichroism of these redistributed electrons using angle resolving electron spectroscopy and modeling the results with the strong-field approximation, this scheme allows to unambiguously determine the absolute degree of circular polarization of any pulsed, ultraintense XUV or X-ray laser source.},
doi = {10.1063/1.4961470},
journal = {Review of Scientific Instruments},
number = 8,
volume = 87,
place = {United States},
year = 2016,
month = 8
}
  • Cited by 5
  • Cited by 5
  • X-ray magnetic circular dichroism spectroscopy using an X-ray free electron laser is demonstrated with spectra over the Fe L{sub 3,2}-edges. The high brightness of the X-ray free electron laser combined with high accuracy detection of incident and transmitted X-rays enables ultrafast X-ray magnetic circular dichroism studies of unprecedented sensitivity. This new capability is applied to a study of all-optical magnetic switching dynamics of Fe and Gd magnetic sublattices in a GdFeCo thin film above its magnetization compensation temperature.
  • In spite of the importance of anisotropic circular dichroism, in practice, it is difficult to get rid of the artifacts that arise from the imperfection of the circular polarization. Undesirable linear dichroism, interference of two orthogonal polarization states, and linear birefringence prevent us from making accurate measurements. We propose a theoretical method for evaluating the contributions of the first two, which are thought to be the main artifacts when specimens are not thick enough. Using the time-dependent perturbation theory and taking into account the direction of light propagation toward an orientationally fixed molecule, we formulated the transition probability of systemsmore » perturbed by arbitrarily polarized light and the absorption difference associated with two kinds of polarized light. We also formulated, as an extension of the dissymmetry factor of circular dichroism, a newly defined dissymmetry factor associated with two arbitrary polarization states. Furthermore, we considered a mixed-state of photon ensemble in which polarization states distribute at a certain width around a certain average. Although the purity of polarization and ellipticity does not correspond immediately, by considering the mixed state it is possible to treat them consistently. We used quantum statistical mechanics to describe the absorption difference for two kinds of photon ensembles and applied the consequent formula to examine the reported experimental results of single-molecule chiroptical responses under discussion in the recent past. The artifacts are theoretically suggested to be sensitive to the incident direction of elliptically polarized light and to the oriented systems, the ellipticity, and the orientation of ellipse. The mixed state has little, if any, effect when the polarization state distribution is narrow.« less