Instrumentation and Controls
Tech 05: Beam Feedback Systems (hardware)
Paper Title Page
MOP263 Fast Orbit Feedback System for the LNLS Storage Ring 597
 
  • L. Sanfelici, F.H. Cardoso, D.D. Felix Ferreira, S.R. Marques, D.O. Tavares
    LNLS, Campinas, Brazil
 
  The Brazilian Synchrotron Light Laboratory (LNLS) is based on a 1.37 GeV storage ring, previously operated by means of a Slow Orbit Feedback System at a maximum rate of 1 correction every 3 seconds. Since photon flux stability is a key issue for light source users, a faster control system was envisaged to provide better beam stability. This work presents an overview of the hardware architecture and the preliminary results achieved with the implementation of a Fast Orbit Feedback System using commercial hardware. BPM signals are acquired in a distributed topology and sent through a deterministic EtherCAT network to a PXI controller, responsible for applying the SVD-based correction matrix multiplication and communicating with the accelerator control system; the calculated current setpoints are sent to the correctors’ power supplies through a second EtherCAT network. FPGA-based acquisition and actuation chassis perform pre-filtering and control on the digitized input and output signals, respectively.  
 
MOP265 The FONT5 Prototype ILC Intra-train Feedback System at ATF2 600
 
  • P. Burrows, R. Apsimon, D.R. Bett, G.B. Christian, B. Constance, C. Perry, J. Resta-López
    JAI, Oxford, United Kingdom
 
  We present the design and beam test results of a prototype beam-based digital feedback system for the Interaction Point of the International Linear Collider. A custom analogue front-end signal processor, FPGA-based digital signal processing boards, and kicker drive amplifier have been designed, built, deployed and tested with beam in the extraction line of the KEK Accelerator Test Facility (ATF2). The system was used to provide orbit correction in y and y' to the train of bunches extracted from the ATF damping ring. We describe the feedback performance in both single and coupled-loop modes and the optimisation of the loop gains.  
 
MOP266 Stripline Kicker Design for NSLS2 Storage Ring 603
 
  • W.X. Cheng, A. Blednykh, S. Krinsky, O. Singh
    BNL, Upton, Long Island, New York, USA
 
  In the NSLS2 storage ring, there are four stripline kickers/pickups. Two long striplines with electrode length of 30cm will be used as bunch-by-bunch transverse feedback actuators. Two short stripline kickers/pickups with 15cm length will mainly used for tune measurement excitation or signal pickup for the beam stability monitor. High shunt impedance of the long stripline kickers is demanded to produce 200μs damping time. Meanwhile the beam impedance should be minimized. The design work for these two types of stripline is discussed in this paper.  
 
MOP267 Fast BPM Data Distribution for Global Orbit Feedback Using Commercial Gigabit Ethernet Technology 606
 
  • R.L. Hulsart, P. Cerniglia, R.J. Michnoff, M.G. Minty
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In order to correct beam perturbations in RHIC around 10Hz, a new fast data distribution network was required to deliver BPM position data at rates several orders of magnitude above the capability of the existing system. The urgency of the project limited the amount of custom hardware that could be developed, which dictated the use of as much commercially available equipment as possible. The selected architecture uses a custom hardware interface to the existing RHIC BPM electronics together with commercially available Gigabit Ethernet switches to distribute position data to devices located around the collider ring. Using the minimum Ethernet packet size and a field programmable gate array (FPGA) based state machine logic instead of a software based driver, real-time and deterministic data delivery is possible using Ethernet. The method of adapting this protocol for low latency data delivery, bench testing of Ethernet hardware, and the logic to construct Ethernet packets using FPGA hardware will be discussed.
 
 
MOP268 RHIC 10 Hz Global Orbit Feedback System 609
 
  • R.J. Michnoff, L. Arnold, C. Carboni, P. Cerniglia, A.J. Curcio, L. DeSanto, C. Folz, C. Ho, L.T. Hoff, R.L. Hulsart, R. Karl, C. Liu, Y. Luo, W.W. MacKay, G.J. Mahler, W. Meng, K. Mernick, M.G. Minty, C. Montag, R.H. Olsen, J. Piacentino, P. Popken, R. Przybylinski, V. Ptitsyn, J. Ritter, R.F. Schoenfeld, P. Thieberger, J.E. Tuozzolo, A. Weston, J. White, P. Ziminski, P. Zimmerman
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Vibrations of the cryogenic triplet magnets at the Relativistic Heavy Ion Collider (RHIC) are suspected to be causing the beam perturbations observed at frequencies around 10 Hz. Several solutions to counteract the effect have been considered in the past, including reinforcing the magnet base support assembly, a mechanical servo feedback system, and a local beam feedback system at each of the two experimental areas. However, implementation of the mechanical solutions would be expensive, and the local feedback system was insufficient since perturbation amplitudes outside the experimental areas were still problematic. A global 10 Hz orbit feedback system is currently under development at RHIC consisting of 36 beam position monitors (BPMs) and 12 small dedicated dipole corrector magnets in each of the two counter-rotating rings. A subset of the system consisting of 8 BPMs and 4 corrector magnets in each ring was installed and successfully tested during the RHIC 2010 run; and the complete system is being installed for the 2011 run. A description of the overall system architecture and results with beam will be discussed.
 
 
MOP269 Design of Longitudinal Feedback Kicker for HLS Storage Ring 612
 
  • W. Xu, D.H. He
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • W. Wu, Y.K. Wu
    FEL/Duke University, Durham, North Carolina, USA
 
  Hefei Light Source (HLS) is a dedicated synchrotron radiation research facility. It is now undergoing a major upgrade. To obtain a better performance of the light source, a longitudinal feedback system will be developed as part of the upgrade project to cure the coupled bunch mode instabilities. In this work, we present a design of the LFB kicker, a waveguide overloaded cavity with two input and two output ports. The cavity design specifications include a central frequency of 969 MHz (4.75 RF frequency), a bandwidth of more than 100 MHz, and a high shunt impedance of 1200 Ω. A study is carried out to find the dependence of the cavity performance on a few critical geometric parameters of the cavity. Since the shape of the vacuum chamber of the HLS storage ring is octagon, a transition from a circular vacuum chamber to an octagon one is built into the end pieces of the cavity to minimize the total cavity length. To lower the required amplifier power, the structure is optimized to obtain a high shunt impedance. The higher order modes of the kicker cavity are also considered during the design.  
 
WEOBN1 Simultaneous Orbit, Tune, Coupling, and Chromaticity Feedback at RHIC 1394
 
  • M.G. Minty, A.J. Curcio, W.C. Dawson, C. Degen, R.L. Hulsart, Y. Luo, G.J. Marr, A. Marusic, K. Mernick, R.J. Michnoff, P. Oddo, V. Ptitsyn, G. Robert-Demolaize, T. Russo, V. Schoefer, C. Schultheiss, S. Tepikian, M. Wilinski
    BNL, Upton, Long Island, New York, USA
  • T. Satogata
    JLAB, Newport News, Virginia, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
All physics stores at the Relativistic Heavy Ion Collider are now established using simultaneous orbit, tune, coupling, and energy feedback during beam injection, acceleration to full beam energies, during the “beta-squeeze” for establishing small beam sizes at the interaction points, and during removal of separation bumps to establish collisions. In this report we describe the major changes made to enable these achievements. The proof-of-principle for additional chromaticity feedback will also be presented.
 
slides icon Slides WEOBN1 [8.054 MB]  
 
WEODN1 Overview of System Specifications for Bunch by Bunch Feedback Systems 1475
 
  • D. Teytelman
    Dimtel, San Jose, USA
 
  Bunch-by-bunch feedback control of coupled-bunch instabilities has become a ubiquitous feature of storage rings, light sources and colliders. Specifying the requirements for these systems demands knowledge of the instability sources and the accelerator operating parameter space. System requirements include the necessary loop gain and bandwidth, kick voltage, and the overall noise floor. Based on these specifications one can select the system BPMs, processing algorithms, power amplifiers and kickers and make tradeoffs of system cost against necessary performance. Through the use of analytical and experimental techniques this talk will illustrate practical and intelligent choices in this specification process. The approach involves experimental characterization of the accelerator at low or moderate beam currents. Measurements are used to calibrate a parameterized analytical beam dynamics model which can be then extrapolated to nominal beam currents with confidence. The speaker will present example results from several recent installations, highlighting the measurements, the model predictions, and the achieved system performance.  
slides icon Slides WEODN1 [1.755 MB]  
 
WEODN3 Performance Optimization for the LNLS Fast Orbit Feedback System 1485
 
  • D.O. Tavares, S.R. Marques
    LNLS, Campinas, Brazil
 
  The Brazilian Synchrotron Light Laboratory (LNLS) has recently commissioned a Fast Orbit Feedback System for its 1.37 GeV third-generation UVX Storage Ring. This paper presents the optimization work which was carried out using the new hardware capabilities. Well known strategies such as singular values conditioning for correction matrix, dynamic control by means of PID or IMC controllers and EVC (Eigenvector constrained) method for minimizing position error in source points were explored. The problem of actuator limitations (saturation and slew rate) was also investigated, providing a new front line for improving orbit stability through feedback.  
slides icon Slides WEODN3 [1.114 MB]  
 
WEODN4 NSLS-II Fast Orbit Feedback with Individual Eigenmode Compensation 1488
 
  • Y. Tian, L.-H. Yu
    BNL, Upton, Long Island, New York, USA
 
  This paper presents the NSLS-II fast orbit feedback system with individual eigenmode compensation. The fast orbit feedback system is a typical multiple-input and multiple-output (MIMO) system. Traditional singular value decomposition (SVD) based fast orbit feedback systems treat each eigenmode the same and the same compensation algorithm is applied to all the eigenmodes. In reality, a MIMO system will have different frequency responses for different eigenmodes and thus it is desirable to design different compensation for each eigenmode. The difficulty with this approach comes from the large amount of computation that needs to be done within the time budget of the orbit feedback system. We designed and implemented the NSLS-II fast orbit feedback (FOFB) system with individual eigenmode compensation by taking advantage of the parallel computation capability of field programmable gate array (FPGA) chips.  
slides icon Slides WEODN4 [1.064 MB]