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Optical Engineering

Dynamic monitoring of grating angle at the National Synchrotron Light Source
Author(s): Shinan Qian; Dario Arena; Joseph Dvorak; Kun Qian
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Paper Abstract

We present a dynamic monitoring method and monitoring system of grating angle, referred to as the Precise Angle Monitor (PAM), at U4B, a soft x-ray spherical grating monochromator (SGM) beam line at the National Synchrotron Light Source (NSLS). In an SGM, a photon energy scan is accomplished by rotating the grating angle precisely. After several decades of service, the monochromator at U4B developed instabilities that severely impacted the experimental program. Over several hours, either the spectral shape experienced distortions or the spectral peak shifted. In order to directly monitor the grating motion during scans, the optical head of a portable long trace profiler (PTLTP) was installed on U4B as the PAM. We find that the grating rotational motion is not ideal: (1) the scan steps are not smooth and there are high-frequency step angle errors; (2) there is also a low-frequency angle error; and (3) an unstable thermal expansion produces extra rotational error. Measurements of dynamic monitoring are presented, including grating rotation repeatability and thermal instability. The results illustrate the utility of dynamic monitoring of monochromator motion during actual operation.

Paper Details

Date Published: 1 November 2009
PDF: 8 pages
Opt. Eng. 48(11) 113603 doi: 10.1117/1.3265548
Published in: Optical Engineering Volume 48, Issue 11
Show Author Affiliations
Shinan Qian, Brookhaven National Lab. (United States)
Dario Arena, Brookhaven National Lab. (United States)
Joseph Dvorak, Brookhaven National Lab. (United States)
Kun Qian, Brookhaven National Lab. (United States)


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