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

Conference · Fri Jan 23 04:00:00 EST 1998

OSTI ID:607504

Sutherland, J C; Polewski, K; Monteleone, D C ^[1]

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1. and others

We have constructed an experimental station (beamline) at the National Synchrotron Light Source to measure circular dichroism (CD) using soft x-rays (250 {le} hv {le} 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 {approx}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.

• Research Organization: Brookhaven National Lab., Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Energy Research, Washington, DC (United States)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 607504
• Report Number(s): BNL--65190; CONF-980117--; ON: DE98004367
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
BEAM PULSERS
DATA ACQUISITION SYSTEMS
MAGNETIC CIRCULAR DICHROISM
MONOCHROMATORS
RADIATION DETECTION
SCATTERING
SOFT X RADIATION
SYNCHROTRON RADIATION
WIGGLER MAGNETS