06 Beam Instrumentation, Controls, Feedback, and Operational Aspects
T05 Beam Feedback Systems
Paper Title Page
TUZGBD2 Transverse and Longitudinal Bunch-by-Bunch Feedback for Storage Rings 1198
  • T. Nakamura
    JASRI/SPring-8, Hyogo-ken, Japan
  Digital bunch-by-bunch feedback systems for betatron and synchrotron oscillation are powerful tools for suppression of beam instabilities and are indispensable for stable operation of storage rings. This invited talk reviews the world activities on transvers and longitudinal bunch-by-bunch feedback for storage rings.  
slides icon Slides TUZGBD2 [15.904 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBD2  
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TUZGBD4 Impact of a Wideband Feedback Prototype System on TMCI in the SPS 1208
  • W. Höfle, H. Bartosik, E.R. Bjørsvik, G. Kotzian, T.E. Levens, K.S.B. Li
    CERN, Geneva, Switzerland
  • J.E. Dusatko, J.D. Fox, C.H. Rivetta
    SLAC, Menlo Park, California, USA
  • O. Turgut
    Stanford University, Stanford, California, USA
  The transverse mode coupling instability (TMCI) in the SPS has been identified as one of the potential performance limitations for future high intensity LHC beams that will be required for the High Luminosity (HL)-LHC era and is being addressed by the LHC Injector Upgrade Project (LIU). A potential mitigation can be provided by wideband feedback systems with a frequency reach of about 1 GHz . For this reason, the development of a prototype system has been started in a CERN collaboration within the US-LARP framework in 2008. In this report we present latest experimental results in 2017 where this prototype system was used in single and multi-bunch studies. In particular, a successful mitigation against TMCI at injection could be demonstrated in single bunch studies.  
slides icon Slides TUZGBD4 [15.120 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBD4  
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TUZGBD5 Performance of Nanometre-Level Resolution Cavity Beam Position Monitors at ATF2 1212
  • T. Bromwich, D.R. Bett, N. Blaskovic Kraljevic, R.M. Bodenstein, P. Burrows, G.B. Christian, C. Perry, R.L. Ramjiawan
    JAI, Oxford, United Kingdom
  • S. Araki, A. Aryshev, T. Tauchi, N. Terunuma
    KEK, Ibaraki, Japan
  • P. Bambade, S. Wallon
    LAL, Orsay, France
  • S.W. Jang
    Korea University Sejong Campus, Sejong, Republic of Korea
  A system of three low-Q cavity beam position monitors (BPMs), installed in the interaction point (IP) region of the Accelerator Test Facility (ATF2) at KEK, has been designed and optimised for nanometre-level beam position resolution. The BPMs are used to provide an input to a low-latency, intra-train beam position feedback system deployed in single-pass, multi-bunch mode with the aim of demonstrating intra-train beam stabilisation on electron bunches of charge ~1 nC separated in time by 280 ns. In 2016 the BPM resolution was demonstrated to be below 50 nm using the raw measured vertical positions at the three BPMs. New results will be presented utilising integrated sampling of the raw waveforms, improved BPM alignment and modified cavities to demonstrate a vertical position resolution on the order of 20 nm.  
slides icon Slides TUZGBD5 [8.561 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBD5  
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WEPAF011 Developments of Bunch by Bunch Feedback System at NSLS-II Storage Ring 1833
  • W.X. Cheng, B. Bacha, Y. Li
    BNL, Upton, Long Island, New York, USA
  • D. Teytelman
    Dimtel, San Jose, USA
  Funding: Work supported by DOE contract No: DE-SC0012704
Transverse bunch-by-bunch (BxB) feedback system has been constructed and in operation since the very beginning of NSLS-II storage ring commissioning. As the total beam current continues increasing in the past years, the system has been operating stable and reliable. Advanced BxB diagnostic functions have been developed using the system. Continuous tune measurement is realized with a diagnostic single bunch. Coupled bunch instability growth rate is able to be measured with the transient excitation. The BxB feedback system is also capable to excite a small fraction of total bunches for lattice measurement during high current operations. We present the most recent developments and operation experience on the BxB feedback system at NSLS-II.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF011  
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WEPAF032 An Alternative Fast Orbit Feedback Design of HEPS 1888
  • X.Y. Huang, J.S. Cao, Y.Y. Du, F. Liu, Y.H. Lu, Y.F. Ma, Y.F. Sui, S.J. Wei, Q. Ye, X.E. Zhang, D.C. Zhu
    IHEP, Beijing, People's Republic of China
  The High Energy Photon Source (HEPS) is a fourth generation light source in China and will be built in this year. The emittance of HEPS storage ring is approaching diffraction limit and the circumstance of the ring is about 1.3 kilometres. To stabilize the electron beam, fast orbit feedback (FOFB) system is prerequisite. In this paper, the requirements on the HEPS beam stability are discussed and an alternative FOFB design based on DBPM are introduced with algorithm and architecture.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF032  
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WEPAF072 Transverse Feedback System for the CERN FCC-hh Collider 1997
  • W. Höfle, J. Komppula, G. Kotzian, K.S.B. Li, D. Valuch
    CERN, Geneva, Switzerland
  For the future hadron Collider (FCC-hh) being studied at CERN a strong transverse feedback system is required to damp coupled bunch instabilities. This system is also planned to be used for injection damping. Based on the LHC transverse feedback design we derive requirements for power and kick strength for this system for the different options of bunch spacing, 25 ns and 5 ns, and injection energy. Operation at high gain and close to a half integer tune is being considered and constrains the layout and signal processing. Requirements for the pick-up resolution are derived from the need to keep the emittance increase small. The performance is evaluated using numerical simulations based on the headtail code. Future areas of research and development and possible prototype developments are outlined.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF072  
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WEPAF073 Ultra-Wideband Transverse Intra-Bunch Feedback: Beginning Development of a Next Generation 8GSa/s System 2001
  • J.E. Dusatko, J.D. Fox
    SLAC, Menlo Park, California, USA
  Funding: US Department of Energy DE-AC02-76SF00515, US LHC Accelerator Research Program, CERN LHC Injector Upgrade Project and the US-Japan Cooperative Program in High Energy Physics.
Building on the success of our 4GSa/s wideband trans-verse feedback system, we have begun development of a next generation ultra-wideband feedback processor which doubles the effective sampling rate to 8GSa/s. This higher sampling rate and proportional increase in analog band-width enable enhanced flexibility and diagnostics for accelerator transverse feedback such as control of higher-order modes, more detailed diagnostic information, im-proved SNR and two channel processing of total charge and orbit signals, with multiple pickups. Though targeted for ongoing transverse intra-bunch instability studies at the CERN SPS with a 1.7ns bunch length, the increased performance paves the way for instability control and diagnostics applications for other machines such as the HL-LHC and FCC. This paper discusses the beginning development process including an evaluation of the high-est speed AtoD and DtoA data converter devices at time of this writing and selection of the devices used in our design. It then describes the architecture of the full 8GSa/s prototype feedback processor and the design approach, which involves using both custom and commercial components enabling rapid and flexible development.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF073  
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WEPAK003 Effect of Model Errors on the Closed Orbit Correction at the SIS18 Synchrotron of GSI 2080
SUSPL057   use link to see paper's listing under its alternate paper code  
  • S.H. Mirza, P. Forck, H. Klingbeil, R. Singh
    GSI, Darmstadt, Germany
  • H. Klingbeil
    TEMF, TU Darmstadt, Darmstadt, Germany
  Funding: Deutscher Akademischer Austauschdienst under contract No. 91605207
A fast closed orbit feedback system (bandwidth in the order of 1 kHz) is under development at the GSI SIS18 synchrotron for the orbit correction from injection to extraction including the acceleration ramp. The static process model, represented as the orbit response matrix (ORM), is subjected to the systematic optics changes during ramp e.g. beta function and phase advance variations at the locations of BPMs and steerers. In addition to these systematic variations, model mismatches may arise from dipole and quadrupole magnet errors, space charge dependent tune shift as well as BPM and steerer calibration errors. In this contribution, the effects of these model errors on the closed orbit correction are investigated which is necessary for the robust stability analysis of the feedback controller. For the robustness tests, the traditional SVD-based matrix pseudo-inversion is compared to a Fourier-based analysis. The results are achieved by detailed simulations in MADX.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAK003  
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WEPAL024 High Precision Beam Parameter Stabilization for P2 at MESA 2209
SUSPL056   use link to see paper's listing under its alternate paper code  
  • R.F.K. Kempf, J. Diefenbach
    IKP, Mainz, Germany
  • K. Aulenbacher
    HIM, Mainz, Germany
  Funding: Cluster of Excellence PRISMA (EXC 1098/2014) German Research Foundation DFG (GRK 2128)
The experiment P2 will measure the weak mixing angle with an all-time high precision via electron-proton scattering. The measured physics asymmetry and its uncertainty has to be corrected by the apparatus' asymmetry, which is generated by helicity correlated fluctuations of the beam parameters position, angle, intensity and energy. This Poster will describe how the high precision of 0.1 ppb of the parity violating asymmetry can be provided by the high precision measurements of the parameters position, angle and intensity.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL024  
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WEPAL025 Development of a Low-Latency, High-Precision, Beam-Based Feedback System Based on Cavity BPMs at the KEK ATF2 2212
SUSPL058   use link to see paper's listing under its alternate paper code  
  • R.L. Ramjiawan, D.R. Bett, N. Blaskovic Kraljevic, R.M. Bodenstein, T. Bromwich, P. Burrows, G.B. Christian, C. Perry
    JAI, Oxford, United Kingdom
  A low-latency, intra-train feedback system employing cavity beam position monitors (BPMs) has been developed and tested at the Accelerator Test Facility (ATF2) at KEK. The feedback system can be operated with either position information from a single BPM to provide local beam stabilisation, or by using position information from two BPMs to stabilise the beam at an intermediate location. The correction is implemented using a stripline kicker and a custom power amplifier, with the feedback calculations being performed on a digital board built around a Field Programmable Gate Array (FPGA). The addition of indium sealing to the BPMs to increase the cavities' Q-values has led to improvements to the BPM system resolution, with current measurements of the resolution of order 20 nm. The feedback performance was tested with beam trains of two bunches, separated by 280 ns and with a charge of ~1 nC. For single- (two-)BPM feedback, stabilisation of the beam has been demonstrated to below 50 nm (41 nm). Ongoing work to improve the feedback performance further will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL025  
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WEPAL037 Simulation Study on Luminosity Feedback for Horizontal Beam Stabilization at Superkekb 2250
  • C.G. Pang, P. Bambade
    LAL, Orsay, France
  • Y. Funakoshi, S. Uehara
    KEK, Ibaraki, Japan
  The SuperKEKB e+ e- collider uses highly focused ultra-low emittance bunches colliding every 4 ns to reach a very high luminosity of 8× 1035 cm-2s-1. It is quite essential to have an orbit feedback system at the Interaction Point (IP) to maintain the optimum overlap between the colliding beams in the presence of ground motion disturbances. For the horizontal motion, a luminosity monitoring system, based on measuring the rate of the Bhabha process at vanishing scattering angle, is developed as input signal to the feedback system. The relative precision needed for this monitor is studied in detail, for the different successive stages of luminosity operation, based on a full simulation of this system, including the detector, DAQ, lock-in amplifier, and feedback control.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL037  
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WEPAL038 First Tests of Superkekb Fast Luminosity Monitors During 2018 Phase-2 Commissioning 2254
  • C.G. Pang, P. Bambade, S. Di Carlo, D. Jehanno, V. Kubytskyi, Y. Peinaud, C. Rimbault
    LAL, Orsay, France
  • Y. Funakoshi, S. Uehara
    KEK, Ibaraki, Japan
  The SuperKEKB e+e- collider aims to reach a very high luminosity of 8× 1035 cm-2s-1, by using highly focused ultra-low emittance bunches colliding every 4 ns, it is essential to have an orbit feedback system at the Interaction Point (IP) to maintain the optimum overlap between two colliding beams. Luminosity monitoring systems including LumiBelle2 and ZDLM as input to dithering feedback system used to stabilize the horizontal orbit at the IP were developed and will be described, including the detectors, mechanical set-up, DAQ. Preliminary measurements and analysis of background and first stage luminosity monitoring data collected will be reported and compared with simulation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL038  
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WEPAL059 Observation and Suppression of Beam Orbit Drift Due to Path Length Changes and Thermal Effect in TPS 2313
  • P.C. Chiu, K.T. Hsu, K.H. Hu, C.H. Huang, C.-C. Kuo
    NSRRC, Hsinchu, Taiwan
  Tidal effect, ambient temperature fluctuation and other effects of the TPS site can cause the path length changes of the electron beam in the TPS storage ring. Off-energy orbit drifts from the path length change, if not varying the RF frequency, cannot be properly corrected by the horizontal correctors and this causes the fast orbit feedback system over its normal working range. RF frequency adjustment loop is therefore applied to compensate for the circumference change based on the accumulating corrector strengths of the fast orbit feedback system. Implementation and operational experiences will be discussed in the report.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL059  
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WEPAL079 Control of Intra-Bunch Vertical Motion in the SPS with GHz Bandwidth Feedback 2365
  • J.D. Fox, J.E. Dusatko, C.H. Rivetta, O. Turgut
    SLAC, Menlo Park, California, USA
  • H. Bartosik, E.R. Bjørsvik, W. Höfle, G. Kotzian, K.S.B. Li, E. Métral, B. Salvant, U. Wehrle
    CERN, Geneva, Switzerland
  • S. De Santis
    LBNL, Berkeley, California, USA
  Funding: Work supported by the U.S. Department of Energy DE-AC02-76SF00515, US LHC Accelerator Research program, CERN LHC Injector Upgrade Project and the US-Japan Cooperative Program in High Energy Physics.
A GHz bandwidth vertical beam feedback system has been in development at the CERN SPS to explore control of unstable beam motion in single bunch and bunch train configurations. We present measurements and recent studies of stable and unstable motion for intensities up to 2x1011 p/bunch. The system has been operated at 3.2GS/s with 16 samples across a 5 ns RF bucket (4.2 ns 3 σ bunch at injection). Experimental results confirm damping of intra-bunch instabilities in Q20, Q22 and Q26 optics configurations. Instabilities with growth times of 200 turns are well-controlled from injection, consistent with the achievable gains for the 2 installed stripline kickers with 1 kW broadband total power. Studies of the damping achieved with the diagonal FIR controllers and existing system noise floors are highlighted to evaluate benefits of MIMO feedback controllers. The work is motivated by anticipated intensity increases from the LIU and HL-LHC upgrade programs, and has included the development of a new 1 GHz bandwidth slotline kicker structure and associated amplifier system
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL079  
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THYGBE4 Early Phase 2 Results of LumiBelle2 for the SuperKEKB Electron Ring 2934
  • S. Di Carlo, P. Bambade, D. Jehanno, V. Kubytskyi, C.G. Pang, Y. Peinaud, C. Rimbault
    LAL, Orsay, France
  We report on the early SuperKEKB Phase 2 operations of the fast luminosity monitor (LumiBelle2 project). Fast luminosity monitoring is required by the dithering feedback system, which is used to stabilize the beam in the presence of horizontal vibrations. In this report, we focus on the operations related to the electron side of LumiBelle2. Diamond sensors are located 30 meters downstream of the IP, just above, beside, and below the electron beam pipe. During early Phase 2, the sensors are used to measure the background, arising from beam-gas scattering. We present the hardware design, the detection algorithm, and the analysis of the background measurements taken up-to-date. The results are then compared with a detailed simulation of the background, in order to well understand the physical processes involved. The simulation is performed using SAD for generation and tracking purposes, while Geant4 is used to calculate the energy deposition in the diamond sensors.  
slides icon Slides THYGBE4 [3.096 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBE4  
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THPML089 Tuning of 3-tap Bandpass Filter During Acceleration for Longitudinal Beam Stabilization at FAIR 4866
  • B.R. Reichardt, D. Domont-Yankulova
    Technische Universität Darmstadt (TU Darmstadt, RMR), Darmstadt, Germany
  • D. Domont-Yankulova, H. Klingbeil
    TEMF, TU Darmstadt, Darmstadt, Germany
  • H. Klingbeil, D.E.M. Lens
    GSI, Darmstadt, Germany
  During acceleration in the heavy-ion synchrotrons SIS18/SIS100 at GSI/FAIR longitudinal beam oscillations are expected to occur. To reduce longitudinal emittance blow-up, dedi- cated LLRF beam feedback systems are planned. To date, damping of longitudinal beam oscillations has been demon- strated in SIS18 machine experiments with a 3-tap filter controller (e.g. *), which is robust in regard to control pa- rameters and also to noise. On acceleration ramps the control parameters have to be adjusted to the varying synchrotron frequency. Previous results from beam experiments at GSI indicate that a proportional tuning rule for one parameter and an inversely proportional tuning rule for a second parameter is feasible, but the obtained damping rate may not be opti- mal for all synchrotron frequencies during the ramp. In this work, macro-particle simulations are performed to evaluate, whether it is sufficient to adjust the control parameters pro- portionally (inversely proportionally) to the change in the linear synchrotron frequency, or if it is necessary to take more pa- rameters, such as bunch-length and synchronous phase, into account to achieve stability and a considerable high damping rate for excited longitudinal dipole beam oscillations. This is done for single- and dual-harmonic acceleration ramps.
* H. Klingbeil et al., "A Digital Beam-Phase Control System for Heavy-Ion Synchrotrons", in IEEE Transactions on Nuclear Science, vol. 54, no. 6, pp. 2604-2610, Dec. 2007.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML089  
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