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 article

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 - Dec 1 1998
EventAdvances in Optical Biophysics - San Jose, CA, United States
Duration: Jan 25 1998Jan 26 1998

Fingerprint

Soft X-ray
Dichroism
dichroism
Scattering
Polarization
X rays
scattering
x rays
Synchrotrons
Light sources
polarization modulation
Switches
Modulation
electric choppers
polarization
Switch
light sources
synchrotrons
switches
stations

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

Cite this

Soft X-ray circular dichroism and scattering using a modulated elliptically polarizing wiggler and double synchronous detection. / Sutherland, John C.; Polewski, Krzysztof; Monteleone, Denise C.; Trunk, John G.; Nintzel, Gary A.; Carlson, Dennis G.; Dong, Qing Li; Singh, Om V.; Hulbert, Steven L.; Kao, Chi Chang; Johnson, Erik D.

In: Proceedings of SPIE - The International Society for Optical Engineering, Vol. 3256, 01.12.1998, p. 2-14.

Research output: Contribution to journalConference article

Sutherland, John C. ; Polewski, Krzysztof ; Monteleone, Denise C. ; Trunk, John G. ; Nintzel, Gary A. ; Carlson, Dennis G. ; Dong, Qing Li ; Singh, Om V. ; Hulbert, Steven L. ; Kao, Chi Chang ; Johnson, Erik D. / Soft X-ray circular dichroism and scattering using a modulated elliptically polarizing wiggler and double synchronous detection. In: Proceedings of SPIE - The International Society for Optical Engineering. 1998 ; Vol. 3256. pp. 2-14.
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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.",
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AU - Sutherland, John C.

AU - Polewski, Krzysztof

AU - Monteleone, Denise C.

AU - Trunk, John G.

AU - Nintzel, Gary A.

AU - Carlson, Dennis G.

AU - Dong, Qing Li

AU - Singh, Om V.

AU - Hulbert, Steven L.

AU - Kao, Chi Chang

AU - Johnson, Erik D.

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N2 - 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.

AB - 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.

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KW - Synchronous detection

KW - Synchrotron radiation

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