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Title: Polarization control in an X-ray free-electron laser

X-ray free-electron lasers are unique sources of high-brightness coherent radiation. However, existing devices supply only linearly polarized light, precluding studies of chiral dynamics. A device called the Delta undulator has been installed at the Linac Coherent Light Source (LCLS) to provide tunable polarization. With a reverse tapered planar undulator line to pre-microbunch the beam and the novel technique of beam diverting, hundreds of microjoules of circularly polarized X-ray pulses are produced at 500–1,200 eV. These X-ray pulses are tens of femtoseconds long, have a degree of circular polarization of 0.98–0.04+0.02 at 707 eV and may be scanned in energy. We also present a new two-colour X-ray pump–X-ray probe operating mode for the LCLS. As a result, energy differences of ΔE/E = 2.4% are supported, and the second pulse can be adjusted to any elliptical polarization. In this mode, the pointing, timing, intensity and wavelength of the two pulses can be modified.
Authors:
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  1. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States); European XFEL GmbH, Hamburg (Germany)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States); Univ. of Gothenburg, Gothenburg (Sweden)
  4. European XFEL GmbH, Hamburg (Germany)
  5. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
  6. SLAC National Accelerator Lab., Menlo Park, CA (United States); Univ. of Bern, Bern (Switzerland)
Publication Date:
OSTI Identifier:
1332904
Report Number(s):
SLAC-PUB-16827
Journal ID: ISSN 1749-4885
Grant/Contract Number:
AC02-76SF00515
Type:
Accepted Manuscript
Journal Name:
Nature Photonics
Additional Journal Information:
Journal Volume: 10; Journal Issue: 7; Journal ID: ISSN 1749-4885
Publisher:
Nature Publishing Group
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACCPHY; XFEL; applied optics; circular dichroism; free-electron lasers; optical physics