06 Instrumentation, Controls, Feedback & Operational Aspects
T05 Beam Feedback Systems
Paper Title Page
TUPME009 A Sub-micron Resolution, Wide-band, Stripline BPM System for Driving Bunch-by-bunch Feed-back and Feed-forward Systems at ATF 1358
 
  • G.B. Christian, D.R. Bett, N. Blaskovic Kraljevic, P. Burrows, M.R. Davis, Y.I. Kim, C. Perry
    JAI, Oxford, United Kingdom
 
  A low-latency, sub-micron resolution stripline beam position monitoring (BPM) system has been developed and tested with beam at the KEK Accelerator Test Facility (ATF2), where it has been used as part of a beam stabilisation system. The fast analogue front-end signal processor is based on a single-stage RF down-mixer and a position resolution below 400 nm has been demonstrated for beam intensities of ~1 nC, with single-pass beam. The BPM position data are digitised by fast ADCs on an FPGA-based digital feedback controller, which is used to drive either a pair of kickers local to the BPMs and nominally orthogonal in phase, in closed-loop feedback mode, or a downstream kicker in the ATF2 final focus region, in feedforward mode. The beam jitter is measured downstream of the final focus system with high resolution, low-Q, cavity BPMs, and the relative performance of both systems in stabilising the beam is compared.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME009  
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TUPRI072 Status and Performance of Bunch-by-bunch Feedback at BESSY II and MLS 1733
 
  • A. Schälicke, P. Goslawski, M. Ries, M. Ruprecht
    HZB, Berlin, Germany
 
  Funding: Work supported by German Bundesministerium für Bildung und Forschung and Land Berlin.
Bunch-by-bunch feedback systems provide an important component in the reliable operation of electron storage rings. Modern digital bunch-by-bunch feedback systems allow efficient mitigation of multi-bunch instabilities, and at the same time offer valuable beam diagnostics. In this contribution, setup and performance of the bunch-by-bunch feedback systems at BESSY II and the MLS are presented. Longitudinal and transverse instabilities are studied under different machine conditions. The developed data analysis techniques and experimental measurements are discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI072  
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TUPRI073 Impact of Simplified Stationary Cavity Beam Loading on the Longitudinal Feedback System for SIS100 1736
 
  • K. Groß, H. Klingbeil, D.E.M. Lens
    TEMF, TU Darmstadt, Darmstadt, Germany
  • H. Klingbeil
    GSI, Darmstadt, Germany
  • D.E.M. Lens
    TU Darmstadt, RTR, Darmstadt, Germany
 
  Funding: Work supported by the German Federal Ministry of Education and Research (BMBF) under the project 05P12RDRBF.
The main synchrotron SIS100 of the Facility for Antiproton and Ion Research (FAIR) will be equipped with a bunch-by-bunch feedback system to damp longitudinal beam oscillations. In the basic layout, one three-tap finite impulse response (FIR) filter will be used for each single bunch and oscillation mode. The detected oscillations are used to generate a correction voltage in dedicated broadband radio frequency (RF) cavities. The digital filter is completely described by two parameters, the feedback gain and the passband center frequency, which have to be defined depending on the longitudinal beam dynamics. In earlier works*, the performance of the closed loop control with such an FIR-filter was analyzed and compared to simulations and measurements with respect to the damping of coherent dipole and quadrupole modes, the first modes of oscillation. This contribution analyzes the influence of cavity beam loading on the closed loop performance and the choice of the feedback gain and passband center frequency to verify future high current operation at FAIR.
* H. Klingbeil et al., IEEE Trans. Nuc. Sci., Vol. 54, No. 6, 2007 and D. Lens et al., Phys. Rev. STAB 16, 032801, 2013.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI073  
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TUPRI074 First Results of the New Bunch-by-bunch Feedback System at ANKA 1739
 
  • E. Hertle, N. Hiller, E. Huttel, B. Kehrer, A.-S. Müller, A.-S. Müller, N.J. Smale
    KIT, Eggenstein-Leopoldshafen, Germany
  • M. Höner
    DELTA, Dortmund, Germany
  • D. Teytelman
    Dimtel, San Jose, USA
 
  A new digital three dimensional fast bunch by bunch feedback system has been installed and commissioned at ANKA. Immediate improvements to stored current and lifetime were achieved for normal user operation. For this, the feedback has to be running during the injection and the energy ramp to 2.5 GeV. Additionally, the feedback system was also incorporated into the diagnostic tool-set at ANKA and opened up new possibilities of automated and continuous measurements of certain beam parameters. The system can operate in different modes such as the low alpha operation mode, which has different requirements on the feedback system compared to normal user operation. Results on the various aspects will be presented as well as future improvements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI074  
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TUPRI075 Beam Orbit Stability at Elettra 1742
 
  • G. Gaio, S. Cleva, E. Karantzoulis, S. Krecic, M. Lonza
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
 
  The top-up operation established since 2010 at the Elettra third-generation synchrotron light source has solved the problems related to thermal drifts and beam current dependence, and a series of feedback loops acting on the machine optics and radio-frequency systems made easier to setup and operate the ring. Those systems together with the fast orbit feedback in operation since 2007, contributed to a very high electron beam orbit stability. A description of the active systems and their performance, future perspectives as well as some still open issues will be presented and discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI075  
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TUPRI077 Stabilization of Mid-infrared FEL by Feedback Controls 1745
 
  • H. Zen, M. Inukai, T. Kii, K. Masuda, M. Mishima, H. Negm, H. Ohgaki, K. Okumura, K. Takami, K. Torgasin, Y. Tsugamura, K. Yoshida
    Kyoto University, Kyoto, Japan
 
  A Mid-Infrared Free Electron Laser facility, KU-FEL* has been developed for energy related sciences. A beam position monitor and feedback system was introduced to stabilize the FEL output power and wavelength. The long term stability of FEL power and wavelength has been drastically improved by the feedback control. The developed feedback system and its performance will be reported in the conference.
*H. Zen, et al., Infrared Physics & Technology, vol.51, 382-385.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI077  
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TUPRI078 Fast Orbit Feedback Application at MAX IV and SOLARIS Storage Rings 1748
 
  • P. Leban, E. Janezic
    I-Tech, Solkan, Slovenia
  • M. Sjöström
    MAX-lab, Lund, Sweden
 
  A common Fast Orbit Feedback (FOFB) application is planned for the new storage rings at MAX IV laboratory and SOLARIS. The application will run in the Beam Position Monitor (BPM) electronics (Libera Brilliance+). Global orbit data concentration will be conducted inside the gigabit data exchange (GDX) modules with a Virtex6 field programmable gate array, which will be daisy-chained around the storage ring. The feedback calculation algorithm is based on the Singular Value Decomposition (SVD) – the PI controller will be applied in the modal space for individual eigenmodes. The calculations will be distributed over all GDX modules to reduce overall latency. Each GDX module will calculate setpoints for four correctors, horizontal or vertical. The new setpoints will be sent directly to the magnet power supply controllers over a serial point-to-point link. This article presents details on FOFB implementation and control topology.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI078  
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TUPRI080 Emittance Optimisation in the Drive Beam Recombination Complex at CTF3 1754
SUSPSNE085   use link to see paper's listing under its alternate paper code  
 
  • D. Gamba, F. Tecker
    CERN, Geneva, Switzerland
  • D. Gamba
    JAI, Oxford, United Kingdom
 
  According to the Conceptual Design Report, the power to accelerate the main colliding beams of CLIC is taken from parallel high intensity (100 A), low energy (2.37 GeV) beams. These beams are generated by long trains, accelerated by conventional klystrons and then time-compressed in the so called Drive-Beam Recombination Complex (DBRC). A scaled version of the DBRC has been built at the CLIC Test Facility (CTF3) at CERN in order to prove its principle and study any arising feasibility issues. One of the main constraints is the emittance control during the recombination process. This work presents an overview of the studies ongoing at CTF3, keeping in view possible improvements of the nominal CLIC design. In particular, a generic feedback algorithm to solve (quasi-)linear systems has been implemented and used in order to optimise the process by tuning the energy of the beam and steer the orbits in the different lines, as well matching the design dispersion. Current results and possible room for further optimisation will be shown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI080  
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TUPRI081 Feed-forward and Feedback Schemes applied to the Diamond Light Source Storage Ring 1757
 
  • M.T. Heron, M.G. Abbott, M.J. Furseman, D.G. Hickin, E.C. Longhi, I.P.S. Martin, G. Rehm, W.A.H. Rogers, A.J. Rose, B. Singh
    DLS, Oxfordshire, United Kingdom
 
  Since initial operation for users in Jan 2007, Diamond Light Source has developed to support a suite of 22 experimental stations. These stations have resulted in the installation of 24 undulators and two superconducting wigglers in the storage ring. To preserve optics, tune and coupling with the operation of these devices has necessitated the implementation of a number of feed-forward and feedback schemes. The implementation and operation of these correction schemes will be described.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI081  
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TUPRI082 Active Optics Stabilisation Measures at the Diamond Storage Ring 1760
 
  • I.P.S. Martin, R. Bartolini, R.T. Fielder, M.J. Furseman, E.C. Longhi, G. Rehm, W.A.H. Rogers, A.J. Rose, B. Singh
    DLS, Oxfordshire, United Kingdom
  • R. Bartolini
    JAI, Oxford, United Kingdom
 
  The Diamond storage ring is currently operated with 26 insertion devices (IDs), including 14 in-vacuum IDs, 7 APPLE-II type helical undulators and 2 superconducting wigglers. Differences in the design, construction and operation of these devices, combined with different Twiss parameters at the source point, mean each has a different impact on tune stability and beta-beat. In turn, these parameters affect the on and off-momentum dynamic aperture and ultimately impact on the injection efficiency and lifetime. Another source of optics variation arises from the coherent tune shift with current, which when injecting from zero current causes the tune to span the available good-tune region. In this paper we discuss the difficulties of operating the Diamond storage ring in top-up mode with these effects, and present the various measures taken to stabilise the storage ring optics.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI082  
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TUPRI085 Development of a 4 GS/s Intra-bunch Instability Control System for the SPS - Next Steps 1766
 
  • J.D. Fox, J.M. Cesaratto, J.E. Dusatko, K.M. Pollock, C.H. Rivetta, O. Turgut
    SLAC, Menlo Park, California, USA
  • S. De Santis
    LBNL, Berkeley, California, USA
  • W. Höfle, G. Kotzian, U. Wehrle
    CERN, Geneva, Switzerland
 
  Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP).
We present the expanded system architecture in development for the control of intra-bunch instabilities in the SPS. Earlier efforts concentrated on validating the performance of a single-bunch demonstration processor. This minimal system was successfully commissioned at the SPS just prior to the LS1 shutdown. The architecture is now in expansion for more complex functionality, specifically multi-bunch control, control during energy ramps, and the expansion of the system front-end dynamic range with more sophisticated orbit offset techniques. Two designs of wideband kicker are being developed for installation and evaluation with the beam. With these GHz bandwidth devices and new RF amplifiers we anticipate being able to excite and control internal motion of the beam consistent with modes expected for Ecloud and TMCI effects. We highlight the expanded features, and present strategies for verifying the behavior of the beam-feedback system in the next series of machine measurements planned after the LS1 shutdown.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI085  
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TUPRI086 Feedback System Design Techniques for Control of Intra-bunch Instabilities at the SPS 1769
 
  • C.H. Rivetta, J.M. Cesaratto, J.E. Dusatko, J.D. Fox, O. Turgut
    SLAC, Menlo Park, California, USA
  • W. Höfle, G. Kotzian, K.S.B. Li
    CERN, Geneva, Switzerland
 
  Funding: Work supported by the U.S. Department of Energy under contract # DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP).
The feedback control of intra-bunch instabilities driven by electron-clouds or strong head-tail coupling requires bandwidth sufficient to sense the vertical position and apply multiple corrections within a nanosecond-scale bunch. These requirements impose challenges and limits in the design and implementation of the feedback system. This paper presents model-based design techniques for feedback systems to address the stabilization of the transverse bunch dynamics. These techniques include in the design the effect of noise and signals perturbing the bunch motion. Different controllers are compared based on stability margins and equivalent noise gain between input-output of the processing channel. The controller design uses as example the bunch dynamics defined by the SPS ring including the Q20 optics.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI086  
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TUPRI087 A Wideband Slotted Kicker Design for SPS Transverse Intra-bunch Feedback 1772
 
  • J.M. Cesaratto, J.D. Fox, C.H. Rivetta
    SLAC, Menlo Park, California, USA
  • D. Alesini, A. Gallo, M. Zobov
    INFN/LNF, Frascati (Roma), Italy
  • S. De Santis
    LBNL, Berkeley, California, USA
  • W. Höfle
    CERN, Geneva, Switzerland
 
  Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP) and by the EU FP7 HiLumi LHC - Grant Agreement 284404.
In order for the SPS to meet the beam intensity demands for the HL-LHC upgrade, control and mitigation of transverse beam instabilities caused by electron cloud and TMCI will be essential. For this purpose a wideband intra-bunch feedback method has been proposed, based on a 4 GS/s front end data acquisition and processing, and on a back end frequency response extending to at least 1 GHz. A slotted type kicker, similar to those used for stochastic cooling, as well as an array of stripline kickers have been considered as the terminal elements of the feedback system. A slotted TEM type kicker has been designed fulfilling the bandwidth and kick strength requirements for the SPS application. In this paper we present an updated version of the design and electromagnetic characteristics, leading into the mechanical design and construction of the kicker occurring later this year.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI087  
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THOAA02 Development of a Low-latency, High-precision, Intra-train Beam Feedback System Based on Cavity Beam Position Monitors 2783
SUSPSNE084   use link to see paper's listing under its alternate paper code  
 
  • N. Blaskovic Kraljevic, D.R. Bett, P. Burrows, G.B. Christian, M.R. Davis, Y.I. Kim, C. Perry
    JAI, Oxford, United Kingdom
 
  A low-latency, intra-train, beam feedback system utilising a cavity beam position monitor (BPM) has been developed and tested at the final focus of the Accelerator Test Facility (ATF2) at KEK. A low-Q cavity BPM was utilised with custom signal processing electronics, designed for low latency and optimal position resolution, to provide an input beam position signal to the feedback system. A custom stripline kicker and power amplifier, and an FPGA-based digital feedback board, were used to provide beam correction and feedback control, respectively. The system was deployed in single-pass, multi-bunch mode with the aim of demonstrating intra-train beam stabilisation on electron bunches of charge ~ 1nC separated in time by c. 280ns. The system has been used to demonstrate beam stabilisation to below the 100nm level. Results of the latest beam tests, aimed at even higher performance, will be presented.  
slides icon Slides THOAA02 [2.050 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THOAA02  
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THOAA03 Transverse Intra-bunch Feedback in the J-PARC MR 2786
SUSPSNE086   use link to see paper's listing under its alternate paper code  
 
  • K. Nakamura
    Kyoto University, Kyoto, Japan
  • Y.H. Chin, T. Obina, M. Okada, M. Tobiyama
    KEK, Ibaraki, Japan
  • T. Koseki, T. Toyama
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • Y. Shobuda
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
 
  We will report the development of a new broadband (bandwidth of around 100MHz) feedback system for suppression of intra-bunch oscillations and reduction of particle losses at the J-PARC Main Ring (MR). A new BPM has been designed based on the exponential coupler stripline type (the diameter of 134 mm and the length of 300 mm) and it is now under fabrication. In this BPM system, the frequency characteristics are corrected using the equalizer as bunch signals are differentiated. The design detail and the performance of the new BPM as well as preparation of newly installed exciter and power amplifiers will be presented. We will also report beam test results of head-tail mode suppression at 3 GeV with the bunch length of 150-250 ns.  
slides icon Slides THOAA03 [1.149 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THOAA03  
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