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Article
Report number	CERN-ATS-2010-193
Title	SPS Ecloud Instabilities - Analysis of machine studies and implications for Ecloud Feedback
Author(s)	Fox, JD (SLAC) ; Bullitt, A (SLAC) ; Mastorides, T (SLAC) ; Ndabashimiye, G (SLAC) ; Rivetta, C (SLAC) ; Turgut, O (SLAC) ; Van Winkle, D (SLAC) ; Byrd, J (LBL, Berkeley) ; Furman, M (LBL, Berkeley) ; Vay, JL (LBL, Berkeley) ; Hofle, W (CERN) ; Rumolo, S (CERN) ; De Maria, R (Brookhaven)
Publication	2010
Imprint	30 May 2010
Number of pages	4
In:	1st International Particle Accelerator Conference, Kyoto, Japan, 23 - 28 May 2010, pp.WEPEB052
Subject category	Accelerators and Storage Rings
Accelerator/Facility, Experiment	CERN SPS
Abstract	The SPS at high intensities exhibits transverse singlebunch instabilities with signatures consistent with an Ecloud driven instability.[1] 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 wideband 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 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.
Copyright/License	publication: (License: CC-BY)

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