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 language | English (US) |
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Pages (from-to) | 2-14 |
Number of pages | 13 |
Journal | Proceedings of SPIE - The International Society for Optical Engineering |
Volume | 3256 |
DOIs | |
State | Published - 1998 |
Externally published | Yes |
Event | Advances in Optical Biophysics - San Jose, CA, United States Duration: Jan 25 1998 → Jan 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