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Secondo, R.

Paper Title Page
DYN00 Feedback Control of SPS E-clouds / Transverse Mode Coupled Instabilities 50
 
  • C. Rivetta, A. Bullitt, J. Fox, T. Mastorides, G. Ndabashimiye, M. Pivi, O. Turgut
    SLAC National Accelerator Laboratory
  • R. Secondo, J. Vay
    LBNL
  • W. Hofle, B. Salvant
    CERN
 
  Electron cloud driven instability can impose limitations on the maximum stored beam current in present and future accelerators. It drives inter-bunch and intra-bunch instabilities. Feedback control techniques have been proposed to mitigate transverse instabilities within a bunch as an extension of techniques used to control inter-bunch (coupled-bunch) instabilities. The US LHC Accelerator Research Program (LARP) has supported a collaboration between US labs and CERN to explore systems to mitigate E-cloud instabilities and transverse mode coupled instability (TMCI ) for the SPS and LHC machines. For intra-bunch (within a bunch) control of nanosecond scale bunch lengths the feedback channel has to be wide-band (GHz range) to be able to measure and control the vertical position of individual sections of a bunch. The design and implementation of the feedback control system involves the modeling and identification of the bunch dynamics, the design of a feedback control algorithm, and the selection of digital and analog hardware that operates in the GHz range. We present the goals of this collaboration and analyze the different research lines to implement and evaluate a full-function prototype feedback system for the SPS. We include details of the feedback system topology and technical limitations, modeling and identification of the bunch dynamics via simulators and machine measurements. We estimate the necessary control bandwidths, and complexity of the processing channel via design considerations for the control algorithm. Very initial efforts at modeling feedback control via reduced bunch models and semi-realistic feedback system specifications are presented.  
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DYN01 Numerical Modeling of E-Cloud Driven Instability and its Mitigation using a Simulated Feedback System in the CERN SPS  
 
  • J. Vay, J. Byrd, M. Furman, R. Secondo, M. Venturini
    LBNL
  • J. Fox, C. Rivetta
    SLAC National Accelerator Laboratory
  • W. Hofle
    CERN
 
  Funding: Supported by the US-DOE under Contract DE-AC02-05CH11231, the US-LHC Accelerator Research Program (LARP) and the SciDAC program ComPASS. Used resources of NERSC and the Lawrencium cluster at LBNL.

Electron clouds impose limitations on current accelerators that may be more severe for future machines, unless adequate measures of mitigation are taken. Recently, it has been proposed to use feedback systems operating at high frequency (in the GHz range) to damp single-bunch transverse coherent oscillations that may otherwise be amplified during the interaction of the beam with ambient electron clouds. We have used the simulation package WARP-POSINST to study the growth rate and frequency patterns in space-time of the electron cloud driven transverse instability in the CERN SPS accelerator with, or without, feedback models (with various levels of idealization) for damping the instability. We will present our latest simulation results, contrast them with actual measurements and discuss the implications for the design of the actual feedback system. More simulations results are presented by Raffaello Secondo using a Finite Impulse Response (FIR) as processing channel in a more realistic, albeit yet highly simplified, model of feedback control system.

 
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DYN02 Simulated Performance of an FIR-Based Feedback System to Control the Electron Cloud Single-Bunch Transverse Instabilities in the CERN SPS 56
 
  • R. Secondo, J. Byrd, M. Furman, M. Venturini, J. Vay
    LBNL
  • J. Fox, C. Rivetta
    SLAC National Accelerator Laboratory
  • W. Hofle
    CERN
 
  The performance of High Energy proton machines like the SPS at CERN is affected by transverse single-bunch instabilities due to the Electron Cloud effect. In a first step to model a Feedback control system to stabilize the bunch dynamics, we use a Finite Impulse Response filter to represent the processing channel. The effect of this simplified processing channel in the bunch dynamics is analyzed using the simulation package WARP-POSINST. We report on simulation results, discuss the basic features of the feedback model and present our plans for further development of the numerical models used in the simulations.  
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