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Proceedings Paper

Soft x-ray circular dichroism and scattering using a modulated elliptically polarizing wiggler and double synchronous detection
Author(s): John Clark 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
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Paper Abstract

We have constructed an experimental station (beamline) at the National Synchrotron Light Source to measure circular dichroism (CD) using soft x-rays (250 less than or equal to hv less than or equal to 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 approximately equals 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.

Paper Details

Date Published: 1 May 1998
PDF: 13 pages
Proc. SPIE 3256, Advances in Optical Biophysics, (1 May 1998); doi: 10.1117/12.307059
Show Author Affiliations
John Clark Sutherland, Brookhaven National Lab. (United States)
Krzysztof Polewski, Brookhaven National Lab. (United States)
Denise C. Monteleone, Brookhaven National Lab. (United States)
John G. Trunk, Brookhaven National Lab. (United States)
Gary A. Nintzel, Brookhaven National Lab. (United States)
Dennis G. Carlson, Brookhaven National Lab. (United States)
Qing-Li Dong, Brookhaven National Lab. (United States)
Om V. Singh, Brookhaven National Lab. (United States)
Steven L. Hulbert, Brookhaven National Lab. (United States)
Chi-Chang Kao, Brookhaven National Lab. (United States)
Erik D. Johnson, Brookhaven National Lab. (United States)


Published in SPIE Proceedings Vol. 3256:
Advances in Optical Biophysics
Joseph R. Lakowicz; J. B. Alexander Ross, Editor(s)

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