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Proceedings Paper

Video-based beam position monitoring at CHESS
Author(s): Peter Revesz; Alan Pauling; Thomas Krawczyk; Kevin J. Kelly
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Paper Abstract

CHESS has pioneered the development of X-ray Video Beam Position Monitors (VBPMs). Unlike traditional photoelectron beam position monitors that rely on photoelectrons generated by the fringe edges of the X-ray beam, with VBPMs we collect information from the whole cross-section of the X-ray beam. VBPMs can also give real-time shape/size information. We have developed three types of VBPMs: (1) VBPMs based on helium luminescence from the intense white X-ray beam. In this case the CCD camera is viewing the luminescence from the side. (2) VBPMs based on luminescence of a thin (~50 micron) CVD diamond sheet as the white beam passes through it. The CCD camera is placed outside the beam line vacuum and views the diamond fluorescence through a viewport. (3) Scatter-based VBPMs. In this case the white X-ray beam passes through a thin graphite filter or Be window. The scattered X-rays create an image of the beam’s footprint on an X-ray sensitive fluorescent screen using a slit placed outside the beam line vacuum. For all VBPMs we use relatively inexpensive 1.3 Mega-pixel CCD cameras connected via USB to a Windows host for image acquisition and analysis. The VBPM host computers are networked and provide live images of the beam and streams of data about the beam position, profile and intensity to CHESS’s signal logging system and to the CHESS operator. The operational use of VBPMs showed great advantage over the traditional BPMs by providing direct visual input for the CHESS operator. The VBPM precision in most cases is on the order of ~0.1 micron. On the down side, the data acquisition frequency (50-1000ms) is inferior to the photoelectron based BPMs. In the future with the use of more expensive fast cameras we will be able create VBPMs working in the few hundreds Hz scale.

Paper Details

Date Published: 15 October 2012
PDF: 10 pages
Proc. SPIE 8502, Advances in X-Ray/EUV Optics and Components VII, 85020G (15 October 2012); doi: 10.1117/12.928508
Show Author Affiliations
Peter Revesz, Cornell Univ. (United States)
Alan Pauling, Cornell Univ. (United States)
Thomas Krawczyk, Cornell Univ. (United States)
Kevin J. Kelly, Univ. of Notre Dame (United States)

Published in SPIE Proceedings Vol. 8502:
Advances in X-Ray/EUV Optics and Components VII
Shunji Goto; Christian Morawe; Ali M. Khounsary, Editor(s)

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