Author: Chubar, O.V.
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TUPAB140 Analysis and Correction of in-Vacuum Undulator Misalignment Effects in a Storage Ring Synchrotron Radiation Source 1663
 
  • O.V. Chubar, T.A. Caswell, Y. Chen-Wiegart, A. Fluerasu, Y. Hidaka, D.A. Hidas, C.A. Kitegi, M.S. Rakitin, T. Tanabe, J. Thieme, L. Wiegart, G. Williams
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work was partially supported by US DOE SBIR grants DE-SC0006284 and DE-SC0011237.
In-vacuum undulators (IVU) are currently very extensively used at different light source facilities, and in particular in medium-energy storage rings, for the production of high-brightness and high-flux hard X-rays. The relatively small (~5 mm or less) vertical magnetic gaps used in these planar undulators make them, however, rather sensitive to the accuracy of alignment of magnet arrays with respect to electron orbit in the vertical plane. Based on results of commissioning of a number of IVUs at hard X-ray beamlines of NSLS-II, their eventual misalignment with respect to the electron orbit was found to be among frequent reasons of spectral underperformance of the beamlines. We will present results of simulations of different IVU misalignment effects on magnetic fields seen by electron beam and on the emitted undulator radiation spectra. The simulations show e.g. that an impact of angular misalignment of an IVU on the radiation spectrum can be minimized if the IVU elevation is selected to make the electron orbit to pass through the IVU magnetic center. Experimental results of spectrum-based alignment of IVUs at hard X-ray beamlines will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB140  
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WEPIK117 A Comprehensive Study of the Microwave Instability 3224
 
  • A. Blednykh, B. Bacha, G. Bassi, O.V. Chubar, M.S. Rakitin, V.V. Smaluk, M. Zhernenkov
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by DOE contract DE-SC0012704
Several instability thresholds and special waveform beam pattern have been observed during measurements of the horizontal beam size change vs single bunch current by the synchrotron light monitor (SLM) camera installed in a low dispersion area of the NSLS-II storage ring. The electron beam energy spread from In-Vacuum Undulator (IVU) of the Soft Matter Interfaces (SMI) beam line confirmed the microwave beam pattern behavior as a current dependent effect. The numerically obtained total longitudinal wakepotential by the GdfidL code allowed us to compare the measured results with particle tracking simulations using the SPACE code. The instability thresholds behavior at different RF voltages are in some sort of overarching agreement.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK117  
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