06 Beam Instrumentation and Feedback
T05 Beam Feedback Systems

Paper	Title	Page
MOPC077	Commissioning of Multibunch Feedback Systems at the Fast Ramping Stretcher Ring ELSA	250
	A. Roth, F. Frommberger, N. Heurich, W. Hillert, M. Schedler, R. Zimmermann ELSA, Bonn, Germany
	Funding: Supported by German Research Foundation through SFB/TR 16 and by Helmholtz Alliance through HA-101. At the Electron Stretcher Facility ELSA of Bonn University, an external beam of either unpolarized or polarized electrons is supplied to hadron physics experiments. The ELSA stretcherring operates in the energy range of 1.2 to 3.5 GeV and achieves a duty cycle of up to 80% using a fast energy ramp of 4 GeV/s. Under these conditions, an increase of the internal beam current from an actual value of 20 mA up to 200 mA is planned. Such an upgrade is mainly limited by the excitation of multibunch instabilities. As one active counteraction, we have installed state-of-the-art bunch-by-bunch feedback systems for the longitudinal, as well as for both transverse planes. The detailed setup with all main components and first results of the commissioning of the systems will be presented. In particular, the performance of the longitudinal feedback with a stabilized synchrotron frequency during the fast energy ramp will be discussed.
MOPO001	Interaction Point Feedback Design and Integrated Simulations to Stabilize the CLIC Final Focus*	475
	G. Balik, L. Brunetti, G. Deleglise, A. Jeremie, L. Pacquet IN2P3-LAPP, Annecy-le-Vieux, France A. Badel, B. Caron, R. Le Breton SYMME, Annecy-le-Vieux, France A. Latina, J. Pfingstner, D. Schulte, J. Snuverink CERN, Geneva, Switzerland
	The Compact Linear Collider (CLIC) accelerator has strong precision requirements on offset position between the beams. The beam which is sensitive to ground motion needs to be stabilized to unprecedented requirements. Different Beam Based Feedback (BBF) algorithms such as Orbit Feedback (OFB) and Beam-Beam Offset Feedback (BBOF) have been designed. This paper focuses on the BBOF control which could be added to the CLIC baseline. It has been tested for different ground motion models in the presence of noises or disturbances and uses digital linear control with or without an adaptive loop. The simulations demonstrate that it is possible to achieve the required performances and quantify the maximum allowed noise level. This amount of admitted noises and disturbances is given in terms of an equivalent disturbance on the position of the magnet that controls the beam offset. Due to the limited sampling frequency of the process, the control loop is in a very small bandwidth. The study shows that these disturbances have to be lowered by other means in the higher frequency range.
MOPO002	Fast Orbit Correction for the ESRF Storage Ring	478
	E. Plouviez, F. Epaud, J.M. Koch, K.B. Scheidt ESRF, Grenoble, France
	Today, at the ESRF, the correction of the orbit position is performed with two independent systems: one to deal with the slow movements and one to correct the motion in a range of up to 200Hz but with a limited number of fast BPMs and steerers. This later will be removed and one unique system will cover the frequency range from DC to 200Hz using all the 224 BPMs and the 96 steerers. Indeed, thanks to the procurement of the Liberas Brilliance and installation of new AC power supplies, it is now possible to access all the Beam positions at a frequency of 10 kHz and to drive a small current in the steerers in a 400Hz bandwidth. The first tests of correction of the beam position have been performed and will be presented. This new orbit correction system is also a powerful diagnostics system: the measurement and survey of the Ring's lattice parameters is possible thanks to the high measurement rate of very high resolution position data. Results of this will also be presented.
MOPO003	A Broadband RF Stripline Kicker for Damping Transversal Multibunch Instabilities	481
	M. Schedler, D. Heiliger, W. Hillert, A. Roth ELSA, Bonn, Germany
	When operating an RF feedback system, being able to reliably act upon every single bunch is a necessity. By employing a broadband RF stripline kicker, any bunch displacement can be corrected for. In a 500 MHz accelerator, the decay time of the electromagnetic field inside the kicker has to be less than 2 ns in order to avoid the following bunch to be affected. By designing the kicker as an RF coax device matched to the line impedance of the power cables, perturbing reflected signals are avoided. Additionally, the kicking strength and thus the shunt impedance should be maximized over the full spectrum from DC to 250 MHz. The kicker design has been optimized to meet the above requirements by relying on CST Microwave Studio simulations. Their results and first measurements are presented.
MOPO004	A Longitudinal Kicker Cavity for a Bunch-by-bunch Feedback System at ELSA	484
	N. Heurich, W. Hillert, A. Roth, R. Zimmermann ELSA, Bonn, Germany
	At the Electron Stretcher Facility ELSA of Bonn University, a longitudinal bunch-by-bunch feedback system is currently being installed in order to damp multibunch instabilities and to enable a future intensity upgrade of up to 200 mA. As a main component, a longitudinal kicker cavity was developed and manufactured. The kicker requires a bandwidth of 250~MHz taking into account the bunch spacing of 2 ns at ELSA. Existing designs used at other facilities were optimized in view of the considerably larger bunch lenght at ELSA. The choice of 1.125 GHz as a center frequency is a result of these considerations. With the resulting low quality factor, the design had to be optimized in order to maximize the shunt impedance. The longitudinal feedback is succesfully working with the prototype installed in the stretcher ring. The design and detailed simulations of the geometry are discussed and laboratory measurements are presented.
MOPO005	A Transverse Feedback System using Multiple Pickups for Noise Minimization	487
	M. Alhumaidi, A.M. Zoubir TU Darmstadt, Darmstadt, Germany
	A new concept for using multiple pickups for estimating beam angle at the kicker is addressed. The estimated signal should be the driving feedback signal. The signals from the different pickups are delayed, such that they correspond to the same bunch. Consequently a weighted sum of the delayed signals is suggested as an estimator of the beam angle at the kicker. The weighting coefficients are calculated such that the estimator is unbiased, i.e. the output corresponds to the actual beam angle at the kicker for non-noisy pickup signals. Furthermore, the estimator must give the minimal noise power at the output among all linear unbiased estimators. Finally results for the heavy ions synchrotron SIS 18 at the GSI are shown.
MOPO006	DAΦNE Bunch-by-bunch Feedback Upgrade as SuperB Design Test	490
	A. Drago INFN/LNF, Frascati (Roma), Italy D. Teytelman Dimtel, San Jose, USA
	DAΦNE, the PHI-factory located in Frascati, has always shown dynamic behavior strongly dependent on the bunch-by-bunch feedback, since its first runs in 1997. Over the years, to keep up with the evolving machine requirements, transverse and longitudinal systems have received multiple upgrades and updates. During fall 2010, all the six DAΦNE feedback systems have been upgraded to support the next run for KLOE as well as to test bunch-by-bunch feedback architectures intended for the future Italian SuperB factory. Both e+/e- longitudinal feedback systems have been completely replaced with new hardware for increased reliability, better diagnostics and improved maintainability. In the effort to reduce residual dipole beam motion, determined by the front-end and quantization noise floor, vertical feedback systems now feature a 12-bit ADC, in place of the older 8-bit design. In the paper, we describe the hardware and software changes of this upgrade. Feedback performance analysis and beam dynamics data collected by the systems are presented.
MOPO007	Resonant Strip-line Type Longitudinal Kicker	493
	T. Nakamura JASRI/SPring-8, Hyogo-ken, Japan
	The longitudinal feedback for the SPring-8 storage ring is under consideration as the device for suppression of the longitudinal instabilities driven by higher order modes of cavities, observed at test operation with 4 to 6 GeV low energy beam. As the beam energy and the ring circumference are rather high, and the length of the space for the longitudinal kickers is limited, high efficiency kicker per length is required in the our case. As a candidate of such kicker, we propose a resonant strip-line type longitudinal kicker with drive frequency of 13/4 of RF frequency. The shut impedance per length is higher than over-loaded cavities and the drive circuits can be simplified because of higher drive frequency. The design consideration, the result of the simulation and measurement of the prototype model, and the detail of the drive circuit will be reported in the presentation.
MOPO008	Design and Simulation of the Transverse Feedback Kicker for the HLSⅡ	496
	W.B. Li, P. Lu, B.G. Sun, F.F. Wu, Y.L. Yang, Z.R. Zhou USTC/NSRL, Hefei, Anhui, People's Republic of China
	In order to suppress the coupled bunch instabilities in the HLSⅡ storage ring, a transverse feedback system is required. The vital component of the system is the kicker that is the feedback actuator. We design a stripline kicker for the HLSⅡ. The horizontal and vertical electrodes are combined in a structure on account of the space limit. In addition to the design issues, this paper focuses on the simulation results for the kicker using the computer codes. By the 2D code POSSION, we calculate and optimize the characteristic impedance of the stripline kicker to match the 50Ω external transmission lines so as to reduce the reflected power. The reflection coefficient and the shunt impedance in the working frequency range are obtained by the 3D code HFSS. The simulation results provide many important supports for the structure design.
MOPO010	Orbit Feedback System for the MAX IV 3 GeV Storage Ring	499
	M. Sjöström, J. Ahlbäck, M.A.G. Johansson, S.C. Leemann, R. Nilsson MAX-lab, Lund, Sweden
	The paper describes the current orbit correction system design for the 3 GeV storage ring at the MAX IV laboratory, a light source facility under construction in Lund, Sweden. The orbit stability requirements for the 3 GeV storage ring are tight at roughly 200 nm vertical position stability in the insertion device (ID) straight sections. To meet this the ring will be equipped with 200 beam position monitors (BPMs) and 380 dipole corrector magnets, 200 in the horizontal and 180 in the vertical plane. The feedback loop solution, one slow orbit feedback (SOFB) loop and one fast orbit feedback (FOFB) loop in fast acquisition mode at 10,000 samples/second, will be presented. The paper will also discuss the various boundary conditions specific to the MAX IV 3 GeV storage ring design, such as a Cu vacuum chamber, and the impact on the corrector design.
MOPO011	The First 1 1/2 Years of TOTEM Roman Pot Operation at LHC	502
	M. Deile, G.H. Antchev, R.W. Assmann, I. Atanassov, V. Avati, J. Baechler, R. Bruce, M. Dupont, K. Eggert, B. Farnham, J. Kaspar, F. Lucas Rodríguez, J. Morant, H. Niewiadomski, X. Pons, E. Radermacher, S. Ravat, F. Ravotti, S. Redaelli, G. Ruggiero, H. Sabba, M. Sapinski, W. Snoeys, G. Valentino, D. Wollmann CERN, Geneva, Switzerland R. Appleby UMAN, Manchester, United Kingdom
	Since the LHC running season 2010, the TOTEM Roman Pots (RPs) are fully operational and serve for collecting elastic and diffractive proton-proton scattering data. Like for other moveable devices approaching the high intensity LHC beams, a reliable and precise control of the RP position is critical to machine protection. After a review of the RP movement control and position interlock system, the crucial task of alignment will be discussed.
MOPO012	LHC Damper Beam Commissioning in 2010	505
	W. Höfle, G. Kotzian, M. Schokker, D. Valuch CERN, Geneva, Switzerland
	The LHC transverse dampers were commissioned in 2010 with beam and their use at injection energy of 450 GeV, during the ramp and in collisions at 3.5 TeV for Physics have become part of the standard operations procedure. The system proved important to limit emittance blow-up at injection and maintain smaller than nominal emittances throughout the accelerating cycle. We describe the commissioning of the system step-by-step as done in 2010 and summarize its performance as achieved for proton as well as ion beams in 2010. Although its principle function is to keep transverse oscillations under control, the system has also been used as an exciter for abort gap cleaning and tune measurement. The dedicated beam position measurement system with its low noise properties provides additional possibilities for diagnostics.
MOPO013	Suppression of Emittance Growth by Excited Magnet Noise with the Transverse Damper in LHC in Simulations and Experiment	508
	W. Höfle, G. Arduini, R. De Maria, G. Kotzian, D. Valuch CERN, Geneva, Switzerland V.A. Lebedev Fermilab, Batavia, USA
	The LHC transverse dampers initially build to control transverse instabilities are also a good remedy to suppress the oscillations causing emittance growth excited by electro-magnetic noises at the frequencies of betatron sidebands. To prevent the emittance growth excited by magnet noise using the damper this system has to have extremely low noise properties. The paper discusses simulation results on the effectiveness of the transverse feedback system to suppress such oscillations and the experimental results from a damper point of view as they were gained during the 2010 LHC run. Possible improvements in the damper system to enhance its effectiveness with respect to the suppression of emittance blow-up are also discussed.
MOPO014	SVD-based Filter Design for the Trajectory Feedback of CLIC	511
	J. Pfingstner, D. Schulte, J. Snuverink CERN, Geneva, Switzerland M. Hofbaur UMIT, Hall in Tirol, Austria
	The orbit feedback of the Compact Linear Collider (CLIC) is the basic counter-measure against ground motion effects below 1 Hz in the beam delivery system and the main linac of CLIC. In this paper we present significant improvements of the orbit feedback design, by using time-dependent and spatial filters. The design procedure is based on a singular value decomposition (SVD) of the orbit response matrix and on loop-shaping techniques. This modified design has essential advantages compared to previous ones. The required beam position monitor resolution in the beam delivery system could be relaxed by a factor of five. At the same time the suppression of ground motion effects is improved. As a consequence, the tight tolerances for the allowable luminosity loss due to ground motion effects in CLIC can be met. The presented methods can be easily adapted to other accelerators in order to relax sensor tolerances and to efficiently suppress ground motion effects.
MOPO015	Operation Status of Bunch-by-bunch Feedback System in the TLS	514
	C.H. Kuo, Y.-S. Cheng, P.C. Chiu, K.T. Hsu, K.H. Hu, C.-Y. Liao NSRRC, Hsinchu, Taiwan
	There are several FPGA based bunch-by-bunch feedback systems that were deployed in the Taiwan Light Source now. They play various roles to suppress beam instability. By using SPring-8 designed feedback processors is pioneer to apply in the storage ring of TLS successfully and help Dimtel system to be quick commission. The Dimtel feedback system provide a life spare unit and explore to control system integration especially to the EPICS toolkit system. Rich functionality includes of excitation of individual bunch or specifies bunches, averaged spectrum, tune measurement by the feedback dip in the averaged spectrum. Operation status of the system will be summary in this report.
MOPO016	Commissioning Tune Feedback in the Taiwan Light Source	517
	C.H. Kuo, J. Chen, Y.-S. Cheng, P.C. Chiu, K.T. Hsu, K.H. Hu, C.-Y. Liao, C.Y. Wu NSRRC, Hsinchu, Taiwan
	The tune control is important parameter in the insertion devices operation. There are many difference type insertion devices are disturbed in the storage ring of TLS. The traditional feed-forward control to correct orbit change and tune shift that isn’t enough when difference type insertion devices are operated with various condition. The tune feedback is used to solve the tune change problem. The stable tune measurement is necessary in the stable storage ring. There are various excited bunch train methods to get stable tune that will be also discussed in this report.
MOPO017	Latest Performance Results from the FONT5 Intra-train Position and Angle Feedback System at ATF2	520
	G.B. Christian, D.R. Bett, M.R. Davis, C. Perry JAI, Oxford, United Kingdom R. Apsimon, P. Burrows Oxford University, Physics Department, Oxford, Oxon, United Kingdom B. Constance, A. Gerbershagen CERN, Geneva, Switzerland J. Resta-López IFIC, Valencia, Spain
	A prototype Interaction Point beam-based feedback system for future electron-positron colliders, such as the International Linear Collider, has been designed and tested on the extraction line of the KEK Accelerator Test Facility (ATF). The FONT5 intra-train feedback system aims to stabilize the beam orbit by correcting both the position and angle jitter in the vertical plane on bunch-to-bunch timescales, providing micron-level stability at the entrance to the ATF2 final-focus system. The system comprises three stripline beam position monitors (BPMs) and two stripline kickers, custom low-latency analogue front-end BPM processors, a custom FPGA-based digital processing board with fast ADCs, and custom kicker-drive amplifiers. An overview of the hardware, and the latest results from beam tests at ATF2, will be presented. A total system latency as low as approximately 140 ns has been demonstrated.
MOPO018	Active Beam Current Stabilization in the Cornell ERL Prototype Injector	523
	F. Löhl, P. Szypryt CLASSE, Ithaca, New York, USA
	In order to operate the Cornell ERL prototype injector at beam currents beyond 10 mA, the beam current has to be highly stable. The reason is that fast beam current fluctuations generate transient effects in the DC gun voltage as well as in the fields of subsequent superconducting cavities, which can lead to excessive beam loss or to trips of subsystems. Therefore, a feedback scheme was developed which uses the signal of a beam current monitor as an input, and applies appropriate corrections to a Pockels cell installed within the laser path of the photo-injector laser. In this paper, high current results achieved with this feedback scheme are presented.
MOPO022	Precision Beam Instrumentation and Feedback-Based Beam Control at RHIC	526
	M.G. Minty, W. Fischer, H. Huang, R.L. Hulsart, C. Liu, Y. Luo, G.J. Marr, A. Marusic, K. Mernick, R.J. Michnoff, V. Ptitsyn, G. Robert-Demolaize, T. Roser, V. Schoefer, S. Tepikian, M. Wilinski 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 this report we present advances in beam instrumentation required for feedback-based beam control at the Relativistic Heavy Ion Collider (RHIC). Improved resolution has contributed to enabling now routine acceleration with multiple feedback loops. Better measurement and control of the beam’s properties have allowed acceleration at a new working point and have facilitated challenging experimental studies.
THOAA02	Implementation of an Intensity Feedback-loop for an Ion-therapy Synchrotron	2851
	C. Schömers, E. Feldmeier, Th. Haberer, J. Naumann, R.E. Panse, A. Peters HIT, Heidelberg, Germany
	The Heidelberg Ion Therapy-Centre (HIT) started treatment of tumour patients in 2009. Its main acceleration stage is a synchrotron, where particles are extracted slowly, in the time frame of some seconds, to support the raster-scanning method. The slow extraction is driven by the transverse "RF-nockout-exciter". So far, this device has a variable but predefined amplitude curve. As the phase-space distribution of particles is not homogeneous and varies slightly from pulse to pulse, intensity-fluctuations of the extracted beam appear. Moreover, changing accelerator-settings requires a time-consuming re-adjustment of the exciter to achieve adequate beam-properties again. To keep the intensity on a predefined level, a feedback loop will be implemented. The actual-value of the intensity is provided by an ionization chamber in front of the patient. The feedback loop controls the amplitude of the Exciter, to adapt the number of extracted particles. Beside a rectangular spill with constant intensity, a dynamic intensity-adaptation during one spill with respect to the particular treatment-plan will be investigated. First tests for flat spill and variable intensity showed promising results.
	Slides THOAA02 [2.284 MB]