Soft X-ray circular dichroism and scattering using a modulated elliptically polarizing wiggler and double synchronous detection

John C. Sutherland, Krzysztof Polewski, Denise C. Monteleone, John G. Trunk, Gary A. Nintzel, Dennis G. Carlson, Qing Li Dong, Om V. Singh, Steven L. Hulbert, Chi Chang Kao, Erik D. Johnson

Research output: Contribution to journalConference articlepeer-review

Abstract

We have constructed an experimental station (beamline) at the National Synchrotron Light Source to measure circular dichroism (CD) using soft x-rays (250 ≤ hv ≤ 900 eV) from a time modulated elliptically polarizing wiggler. The polarization of the soft x-ray beam switches periodically between two opposite polarizations, hence permitting the use of phase-sensitive (lock-in) detection. While the wiggler can be modulated at frequencies up to 100 Hz, switching transients limit the actual practical frequency to ≈ 25 Hz. With analog detection, switching transients are blocked by a chopper synchronized to the frequency and phase of the wiggler. The CD is obtained from the ratio of the signal recovered at the frequency of polarization modulation, f, to the average beam intensity, which is recovered by synchronous detection at frequency 2f.

Original languageEnglish (US)
Pages (from-to)2-14
Number of pages13
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume3256
DOIs
StatePublished - 1998
EventAdvances in Optical Biophysics - San Jose, CA, United States
Duration: Jan 25 1998Jan 26 1998

Keywords

  • Circular dichroism
  • Synchronous detection
  • Synchrotron radiation
  • X-rays

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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