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Title SPS Ecloud Instabilities - Analysis of Machine Studies and Implications for Ecloud Feedback Submitted 06-DEC-09 16:51 (UTC)
Classification 06 Beam Instrumentation and Feedback Modified 08-DEC-09 19:34 (UTC)
Presentation Poster
Presenter John Fox Paper ID WEPEB052
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Author(s) John Fox, Alex Bullitt, Themis Mastorides, Georges Ndabashimiye, Claudio Hector Rivetta, Ozhan Turgut, Daniel Van Winkle (SLAC, Menlo Park, California), Riccardo De Maria (BNL, Upton, Long Island, New York), Wolfgang Höfle, Giovanni Rumolo (CERN, Geneva), John Byrd, Miguel Furman, Jean-Luc Vay (LBNL, Berkeley, California)
Abstract The SPS at high intensities exhibits transverse single-bunch instabilities with signatures consistent with an Ecloud driven instability. We present recent MD data from the SPS, details of the instrument technique and spectral analysis methods which help reveal complex vertical motion that develops within a subset of the injected bunch trains. The beam motion is detected via wide-band exponential taper striplines and delta-sigma hybrids. The raw sum and difference data is sampled at 50 GHz with 1.8 GHz bandwidth. Sliding window FFT techniques and RMS motion techniques show the development of large vertical tune shifts on portions of the bunch of nearly 0.025 from the base tune of 0.185. Results are presented via spectrograms and rms bunch slice trajectories to illustrate development of the unstable beam and time scale of development along the injected bunch train. The study shows that the growing unstable motion occupies a very broad frequency band of 1.2 GHz. These measurements are compared to numerical simulation results, and the system parameter implications for an Ecloud feedback system are outlined.
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Funding Agency Work supported by Department of Energy contracts DE--AC03--76SF00515 DE-AC02-05CH11231 and the US LHC Accelerator Research Program (LARP).

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