IPAC2012 - List of Keywords (feedback)

Paper	Title	Other Keywords	Page
MOOAA03	Fast Feedback Strategies for Longitudinal Beam Stabilization	controls, laser, electron, free-electron-laser	26
	S. Pfeiffer, M.K. Bock, H. Schlarb, Ch. Schmidt DESY, Hamburg, Germany W. Jałmużna TUL-DMCS, Łódź, Poland G. Lichtenberg, H. Werner TUHH, Hamburg, Germany
	The key for pump-probe and seeding experiments at Free Electron Lasers such as FLASH is a femtosecond precise regulation of the bunch arrival time and compression. To maintain this beam based requirements, both for a single bunch and within a bunch train, it is necessary to combine field and beam based feedback loops. We present in this paper an advancement of the currently implemented beam based feedback system at FLASH. The principle of beam based modulation of the RF set point can be superimposed by a direct feedback loop with a beam optimized controller. Recent measurements of the achieved bunch arrival time jitter reduction to 20 fs have shown the performance gain by this direct feedback method . The combination of both approaches will be presented and possible advantages are discussed. C. Schmidt et al., “Feedback Strategies for Bunch Arrival Time Stabilization at FLASH Towards 10 fs,” FEL’2011, Shanghai, August 2011, THPA26, http://www. JACoW.org.
	Slides MOOAA03 [0.544 MB]

MOEPPB015	Excitation of Intra-bunch Vertical Motion in the SPS - Implications for Feedback Control of Ecloud and TMCI Instabilities	resonance, pick-up, betatron, synchrotron	112
	J.D. Fox, J.M. Cesaratto, M.T.F. Pivi, C.H. Rivetta, O. Turgut, S. Uemura SLAC, Menlo Park, California, USA W. Höfle, 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). Electron cloud and transverse mode coupled-bunch instabilities (TMCI) limit the bunch intensity in the CERN SPS. Intra-bunch fast feedback systems are a possible method to control these effects. This paper presents experimental measurements of single-bunch motion in the SPS driven by a GHz bandwidth vertical excitation system. The primary goal is to quantify the change in internal bunch dynamics as instability thresholds are approached, and quantify the frequencies of internal modes as Ecloud effects become significant. The beam response is sampled at 20 GS/sec. in response to arbitrary excitation patterns, with data in 2011 taken at 3 bunch intensities. We show the excitation of barycentric, head-tail and higher vertical modes. The beam motion is analyzed in the time domain, via animated presentations of the sampled vertical signals, and in the frequency domain, via spectrograms showing the modal frequencies vs. time. The demonstration of the excitation of selected internal modes is a significant step in development of the feedback control techniques. "A 4 GS/Sec. Synchronized Vertical Excitation System for SPS Studies - Steps Towards Wideband Feedback," these proceedings.

MOPPC012	Reliability and Intervention Management for the LHC	controls, radiation, status, site	148
	K. Foraz, J.R. Cook, J. Coupard, B. Daudin, J. De Jonghe, F. B. Dos Santos Pedrosa, E.R. Fuentes, C. Garino, K. Golikov, S. Grillot, M.R. Jaekel, P. Sollander CERN, Geneva, Switzerland
	Since 2010, CERN has entered a mode of continuous operation of the LHC and its injectors, which implies the continuous operation of all the infrastructure and support systems. High reliability of the machines is crucial to meet the physics goals. This high reliability must be accompanied by a fast restart after programmed stops. Since 2010, an important effort has been put in place, to ease the coordination process during the programmed stops and to reinforce the management of the interventions (preparation, approval, follow-up, traceability, closure). This paper describes the difficulties from the first year related to this coordination, and the impact on operation. The tools developed for the management of the interventions, their assets and the effect on the reliability of the LHC will also be presented and discussed.

MOPPC015	Proposal for an RF Roadmap Towards Ultimate Intensity in the LHC	cavity, klystron, injection, beam-loading	154
	P. Baudrenghien, T. Mastoridis CERN, Geneva, Switzerland
	The LHC is currently operated with 1380 bunches at 50 ns spacing and 1.4 E11 p per bunch (0.35A DC). In this paper the RF operation with ultimate bunch intensity (1.7 E11 p per bunch) and 25 ns spacing (2808 bunches per beam) summing up to 0.86A DC is presented. With the higher beam current, the demanded klystron power will be increased and the longitudinal stability margin reduced. In addition one must consider the impact of a klystron trip (voltage and power transients in the three turns latency before the beam is actually dumped). In this work a scheme is proposed that can deal with ultimate bunch intensity, without modification to the RF power system. Only a minor upgrade of the LLRF will be necessary: the field set point will be modulated according to the phase shift produced by the transient beam loading, thus minimizing the requested RF power while keeping the strong feedback for stability and reduction of RF noise.

MOPPC017	Causes and Solutions for Emittance Blow-Up During the LHC Cycle	emittance, injection, luminosity, proton	160
	M. Kuhn Uni HH, Hamburg, Germany G. Arduini, B.J. Holzer, J.M. Jowett, V. Kain, F. Roncarolo, M. Schaumann, R. Versteegen, J. Wenninger CERN, Geneva, Switzerland
	Emittance measurements during the run 2011 indicated a blow-up of 20 % to 30 % from LHC injection to collisions. At the LHC design stage the total allowed emittance increase through the cycle was set to 7 %. One of the goals of the 2012 LHC run is therefore to understand and counteract the blow-up. Emittance growth measurements through the LHC cycle along with correlations with possible sources are presented in this paper. Solutions are proposed where possible. The emittance determination accuracy relies on the knowledge of the beam optics and on the present performance of the transverse profile monitors. Possible improvements of the diagnostics and of the related data analysis are also discussed.

MOPPD051	Performance of Resonant Slow Extraction from J-PARC Main Ring	extraction, quadrupole, proton, septum	481
	M. Tomizawa, Y. Arakaki, T. Kimura, S. Murasugi, R. Muto, H. Nakagawa, K. Okamura, H. Sato, Y. Shirakabe, T. Toyama, E. Yanaoka, M. Yoshii KEK, Ibaraki, Japan D. Horikawa Sokendai, Ibaraki, Japan K. Mochiki Tokyo City University, Tokyo, Japan A. Schnase JAEA/J-PARC, Tokai-mura, Japan
	Proton beam accelerated by the J-PARC main ring (MR) with an imaginary transition lattice is slowly extracted by a third integer resonant extraction scheme and delivered to the hadron experimental hall. One of the critical issues in the slow extraction from a high intensity proton synchrotron is the inevitable beam loss caused by the extraction process at septum devices. A design with low beam loss (high extraction efficiency) is required to reduce machine damage and radiation exposure during hands-on maintenance. We have designed the slow extraction scheme to obtain high extraction efficiency for the MR lattice. The scheme has a large step size and a small angular spread enabling a hit rate of the beam on the developed thin septum device. Since the first 30 GeV proton beam was successfully delivered to the experimental hall in January 2009, an extremely high extraction efficiency of 99.5% has been achieved by an intensive beam tuning. In this paper, we report details of such performance. We will also describe some schemes to improve the serious spiky spill time structure due to large current ripples from the power supplies for the bending and quadrupole magnets.

MOPPD071	Error Localization in RHIC by Fitting Difference Orbit	storage-ring, closed-orbit, dipole, optics	526
	C. Liu, M.G. Minty, V. Ptitsyn 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. Many errors in an accelerator are evidenced as transverse kicks to the beam, which distort the beam trajectory. Therefore, the information of the errors are imprinted in the distorted orbits, which are different from what would be predicted by the optics model. In this paper, we introduce an algorithm for fitting the orbit based on an on-line optics model. We apply the algorithm to localize the location of the elusive source of vertical diurnal variations observed in RHIC, and analyze D0/Dx errors in local coupling measurement.

MOPPR015	Bunch-by-bunch Feedback Systems at the DELTA Storage Ring	kicker, electron, synchrotron, injection	807
	M. Höner, M. Bakr, H. Huck, S. Khan, R. Molo, A. Nowaczyk, A. Schick, P. Ungelenk, M. Zeinalzadeh DELTA, Dortmund, Germany
	Funding: Work supported by BMBF (05K10PEB) At the DELTA 1.5-GeV electron storage ring operated as a synchrotron radiation source by the TU Dortmund University, bunch-by-bunch feedback systems have been recently installed and commissioned to detect and suppress longitudinal as well as transverse multibunch instabilities. Besides that, the feedback systems are used as a diagnostics tool. Growth rates of multibunch instabilities and their dependence on the beam current have been measured. Additionally, the oscillation amplitudes of electron bunches have been studied during the injection process.

MOPPR021	Commissioning of a New Beam-position Monitoring System at ANKA	booster, controls, brilliance, synchrotron	825
	S. Marsching, N. Hiller, E. Huttel, V. Judin, B. Kehrer, M. Klein, C.A.J. Meuter, A.-S. Müller, M.J. Nasse, M. Schuh, N.J. Smale, M. Streichert KIT, Karlsruhe, Germany G. Rehm Diamond, Oxfordshire, United Kingdom
	A new beam-position monitoring and diagnostic system is being commissioned at ANKA, the synchrotron light source of the Karlsruhe Institute of Technology. This system is based on 40 Libera Brilliance devices from Instrumentation Technologies. It provides turn-by-turn information about the beam position. This information can be used for beam diagnostics (e.g. finding the position where the beam is lost during injection phase) and can also form the base of a fast orbit-correction scheme. We have performed studies to assess the performance of the new BPM system in comparison to the old system being replaced. In order to optimize the commissioning process we have developed a scheme for switching to the new system gradually by integrating it with the MATLAB Middle-Layer using EPICS control software. In this contribution we present the results of our comparison of the two BPM systems and provide an insight into the experience gained during the commissioning process.

MOPPR032	Electron Beam Diagnostics based on Transverse Feedback System at Duke Storage Ring	storage-ring, electron, monitoring, FEL	849
	W. Xu, D.H. He USTC/NSRL, Hefei, Anhui, People's Republic of China J.Y. Li, W. Wu, Y.K. Wu FEL/Duke University, Durham, North Carolina, USA
	Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033. To combat electron beam instabilities, a field programmable gate array (FPGA) based bunch-by-bunch transverse feedback (TFB) has been developed for the Duke storage ring. While it is capable of suppressing transverse beam instabilities for multi-bunch operation, the TFB system has not been needed for typical operation of the Duke storage ring FEL. To explore the great potential of this system, we have focused on the development of TFB based beam diagnostics. A TFB based tune measurement system has been developed using two methods: the tune scan method and tune monitoring method. With the tune monitoring method, a much faster method of the two, we have studied the tune stability of the electron beam in the Duke storage ring. This tune measurement system also allows us to conduct chromaticity measurements more quickly, compared with the existing chromaticity measurement system using a network analyzer. Finally, the TFB based tune system has been used to calibrate the tune knob and chromaticity knob for the Duke storage ring.

MOPPR036	Correlation Analysis of Beam Diagnostic Measurements in SSRF	status, lattice, diagnostics, background	858
	Z.C. Chen, Y.B. Leng, Y.B. Yan SSRF, Shanghai, People's Republic of China B.P. Wang SINAP, Shanghai, People's Republic of China
	Funding: Supported by National Natural Science Foundation of China (11075198) Signals from various probes of the beam diagnostic system in Shanghai Synchrotron Radiation Facility (SSRF) were processed with correlation analysis algorithms. The resulting data allowed us to sort the probes by confidence, which means the stable and accurate signals could be separated from the faulty or noisy ones. And the beam dynamics measurements became electronic instrument free at the same time. This makes it possible to eliminate bad Beam Position Monitors (BPM) from the feedback system, offer a more confident set of beam parameters and estimate useful global information by extracting the relationship between some probes.

MOPPR042	Characterization Tests of a Stripline Beam Position Monitor for the CLIC Drive Beam	impedance, quadrupole, extraction, simulation	873
	A. Benot-Morell, A. Faus-Golfe, J.J. García-Garrigós IFIC, Valencia, Spain A. Benot-Morell, L. Søby CERN, Geneva, Switzerland J.M. Nappa, J. Tassan-Viol, S. Vilalte IN2P3-LAPP, Annecy-le-Vieux, France S.R. Smith SLAC, Menlo Park, California, USA
	Funding: FPA2010-21456-C02-01, SEIC-2010-00028 A prototype of a stripline Beam Position Monitor (BPM) with its associated readout electronics has been developed at CERN in collaboration with SLAC, LAPP and IFIC. In this paper, the design and simulations of the BPM with the analog readout chain and the BPM test bench are described, and the results of the first characterization tests are presented. The position resolution and accuracy parameters are expected to be below 2μm and 20μm respectively for a beam with a bunching frequency of 12GHz, an average current of 101A and a machine repetition rate of 50Hz.

MOPPR052	Integration Design of BPM and Orbit Feedback Electronic for the TPS	power-supply, controls, EPICS, brilliance	900
	C.H. Kuo, P.C. Chiu, K.T. Hsu, K.H. Hu, C.Y. Wu NSRRC, Hsinchu, Taiwan
	TPS (Taiwan Photon Source) is a 3 GeV synchrotron light source which is being in construction at NSRRC. The orbit measurement and control must be precise much than before in the TPS. New BPM electronic design with the latest generation FPGA and new mechanical form factor to enhance functionality of current generation products will be employed for the TPS. The prototype BPM electronics is testing in the TLS. These testing experiences will be applied in the TPS BPM electronic and software modification. To achieve the stringent orbit stability goal of the TPS, orbit feedback system is designed to eliminate beam motions due to various perturbation sources. The new orbit feedback system is merged to BPM electric system. This design will be enhanced to hardware reliability and fast data exchange performance. The design and implementation plan of the BPM system and the orbit feedback system are summarized in this report.

MOPPR064	Development of a Turn-by-Turn Beam Position Monitoring System for Multiple Bunch Operation of the ATF Damping Ring	extraction, damping, synchrotron, monitoring	930
	P. Burrows, R. Apsimon, D.R. Bett, N. Blaskovic Kraljevic, G.B. Christian, M.R. Davis, A. Gerbershagen, C. Perry JAI, Oxford, United Kingdom B. Constance CERN, Geneva, Switzerland J. Resta-López IFIC, Valencia, Spain
	An FPGA-based monitoring system has been developed to study multi-bunch beam instabilities in the damping ring (DR) of the KEK Accelerator Test Facility (ATF). The system utilises a stripline beam position monitor (BPM) and a single-stage down-mixing BPM processor. The system is designed to record the horizontal and/or vertical positions of up to three bunches in the DR with c. 150ns bunch spacing, or the head bunch of up to three trains in a multi-bunch mode with bunch spacing of 5.6 ns. The FPGA firmware and data acquisition software allow the recording of turn-by-turn data. An overview of the system and performance results will be presented.

MOPPR065	A Low-latency Sub-micron Resolution Stripline Beam Position Monitoring System for Single-pass Beamlines	monitoring, linear-collider, extraction, collider	933
	P. Burrows, D.R. Bett, N. Blaskovic Kraljevic, G.B. Christian, M.R. Davis, A. Gerbershagen, C. Perry JAI, Oxford, United Kingdom R. Apsimon, B. Constance CERN, Geneva, Switzerland J. Resta-López IFIC, Valencia, Spain
	A low-latency, sub-micron resolution stripline beam position monitoring system has been developed for use in single-pass beamlines. The fast analogue front-end signal processor is based on a single-stage RF down-mixer and is combined with an FPGA-based system for digitisation and further signal processing. The system has been deployed and tested with beam at the Accelerator Test Facility at KEK. Performance results are presented on the calibration, resolution and stability of the system. A detailed simulation has been developed that is able to account for the measured performance.

MOPPR066	Study of Transverse Pulse-to-Pulse Orbit Jitter at the KEK Accelerator Test Facility 2 (ATF2)	simulation, extraction, controls, linear-collider	936
	J. Resta-López, J. Alabau-Gonzalvo IFIC, Valencia, Spain R. Apsimon, B. Constance, A. Gerbershagen CERN, Geneva, Switzerland D.R. Bett, P. Burrows, G.B. Christian, M.R. Davis, C. Perry JAI, Oxford, United Kingdom
	Funding: FPA2010-21456-C02-01 For future linear colliders the precise control and mitigation of pulse-to-pulse orbit jitter will be very important to achieve the required luminosity. Diagnostic techniques for the orbit jitter measurement and correction for multi-bunch operation are being addressed at the KEK Accelerator Test Facility 2 (ATF2). In this paper we present recent studies on the vertical jitter propagation through the ATF2 extraction line and final focus system. For these studies the vertical pulse-to-pulse position and angle jitter have been measured using the available stripline beam position monitors in the beamline. The cases with and without intra-train orbit feedback correction in the ATF2 extraction line are compared.

MOPPR080	Wire Scanner Beam Profile Measurements: LANSCE Facility Beam Development	electron, controls, target, linac	975
	J.D. Gilpatrick, Y.K. Batygin, F. Gonzales, M.E. Gruchalla, V.G. Kutac, D. Martinez, C. Pillai, S. Rodriguez Esparza, J.D. Sedillo, B.G. Smith LANL, Los Alamos, New Mexico, USA
	Funding: Work supported by the U.S. Department of Energy. The Los Alamos Neutron Science Center (LANSCE) is replacing Wire Scanner (WS) beam profile measurement systems. Three beam development tests have taken place to test the new wire scanners under beam conditions. These beam development tests have integrated the WS actuator, cable plant, electronics processors and associated software and have used H⁻ beams of different beam energy and current conditions. In addition, the WS measurement-system beam tests verified actuator control systems for minimum profile bin repeatability and speed, checked for actuator backlash and positional stability, tested the replacement of simple broadband potentiometers with narrow band resolvers, and tested resolver use with National Instruments Compact Reconfigurable Input and Output (cRIO) Virtual Instrumentation. These beam tests also have verified how trans-impedance amplifiers react with various types of beam line background noise and how the cable plants can be simplified without generating unwanted noise currents. This paper will describe these beam development tests and show some resulting data.

TUXA02	Upgrade Plans for the LHC Injector Complex	linac, injection, electron, vacuum	1010
	R. Garoby, H. Damerau, S.S. Gilardoni, B. Goddard, K. Hanke, A.M. Lombardi, M. Meddahi, B. Mikulec, E.N. Shaposhnikova, M. Vretenar CERN, Geneva, Switzerland
	Challenging beams with much higher brightness than today are required for the LHC to achieve its high luminosity objective after the year 2020. It is the purpose of the LHC Injectors Upgrade (LIU) Project to achieve this result, consolidating and upgrading the existing set of ageing synchrotrons (PSB, PS and SPS), and using the new linac presently in construction (Linac4). The anticipated beam characteristics are described and compared to the known limitations in the different accelerators. The foreseen solutions are outlined as well as the planning for their implementation.
	Slides TUXA02 [72.367 MB]

TUYA03	Performance and Prospects of BEPCII	luminosity, coupling, optics, injection	1030
	Q. Qin IHEP, Beijing, People's Republic of China
	BEPCII, the upgrade project of Beijing Electron Positron Collider (BEPC), has been put into operation for both high energy physics experiments as well as synchrotron radiation application since its completion in 2009. The peak luminosity reaches 6.5*10³² cm^-2 s^-1 at 1.89 GeV with e⁺e⁻ collisions of each beam current 700 mA. The collider operates for dedicated synchrotron radiation mode with 250 mA electron beams at 2.5 GeV. The performance of BEPCII should be reported and the measures to upgrade its luminosity described.
	Slides TUYA03 [5.529 MB]

TUOAB01	Timing and Synchronization for the APS Short Pulse X-ray Project	laser, cavity, LLRF, storage-ring	1077
	F. Lenkszus, N.D. Arnold, T.G. Berenc, G. Decker, E.M. Dufresne, R.I. Farnsworth, Y.L. Li, R.M. Lill, H. Ma ANL, Argonne, USA J.M. Byrd, L.R. Doolittle, G. Huang, R.B. Wilcox LBNL, Berkeley, California, USA
	Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Short-Pulse X-ray (SPX) project, which is part of the APS upgrade, will provide intense, tunable, high-repetition-rate picosecond x-ray pulses through the use of deflecting cavities operating at the 8th harmonic of the storage-ring rf. Achieving this picosecond capability while minimizing the impact to other beamlines outside the SPX zone imposes demanding timing and synchronization requirements. For example, the mismatch between the upstream and downstream deflecting cavities' rf field phase is specified to be less than 0.077 degrees root mean squared (rms) at 2815 MHz (~77 femtoseconds). Another stringent requirement is to synchronize beamline pump-probe lasers to the SPX x-ray pulse to 400 femtoseconds rms. To achieve these requirements we have entered into a collaboration with the Beam Technology group at LBNL. They have developed and demonstrated a system for distributing stable rf signals over optical fiber capable of achieving less than 20 femtoseconds rms drift and jitter over 2.2 km over 60 hours. This paper defines the overall timing/synchronization requirements for the SPX and describes the plan to achieve them. R. Wilcox et al. Opt. Let. 34(20), Oct 15, 2009
	Slides TUOAB01 [2.515 MB]

TUEPPB006	Direct Numerical Modeling of E-Cloud Driven Instability of Three Consecutive Batches in the CERN SPS	electron, simulation, emittance, betatron	1125
	J.-L. Vay, M.A. Furman, M. Venturini LBNL, Berkeley, California, USA
	Funding: Supported by the US-DOE under Contract DE-AC02-05CH11231, the SciDAC program ComPASS and the US-LHC Accelerator Research Program (LARP). Electron clouds impose limitations on current accelerators that may be more severe for future machines, unless adequate measures of mitigation are taken. The simulation package WARP-POSINST was recently upgraded for handling multiple bunches and modeling concurrently the electron cloud buildup and its effect on the beam, allowing for direct self-consistent simulation of bunch trains generating, and interacting with, electron clouds. We have used the WARP-POSINST package on massively parallel supercomputers to study the buildup and interaction of electron clouds with a proton bunch train in the CERN SPS accelerator. Results suggest that a positive feedback mechanism exists between the electron buildup and the e-cloud driven transverse instability, leading to a net increase in predicted electron density. Used resources of NERSC.

TUPPC061	Commissioning of a beta∗ Knob for Dynamic IR Correction at RHIC	optics, luminosity, quadrupole, insertion	1314
	G. Robert-Demolaize, A. Marusic, S. Tepikian, S.M. White 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 addition to the recent optics correction technique demonstrated at CERN and applied at RHIC, it is important to have a separate tool to control the value of the beta functions at the collision point (beta∗). This becomes even more relevant when trying to reach high level of integrated luminosity while dealing with emittance blow-up over the length of a store, or taking advantage of compensation processes like stochastic cooling. Algorithms have been developed to allow modifying independently the beta function in each plane for each beam without significant increase in beam losses. The following reviews the principle of such algorithms and their experimental implementation as a dynamic beta-squeeze procedure.

TUPPC091	Simulation of Colliding Beams with Feedback in LHC	simulation, emittance, luminosity, kicker	1374
	S. Paret, J. Qiang LBNL, Berkeley, California, USA
	Funding: This work supported partially by the US LHC Accelerator Research Program (LARP) of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Beam-beam effects impose restrictions on beam and beam optical parameters as they may degrade the luminosity and the emittance or cause coherent instabilities and particle loss. In the planned High Luminosity Large Hadron Collider (HL-LHC), beam-beam effects will significantly affect the beams because of unprecedented beam parameters and new features like crab cavities or elliptical beam cross sections at the interaction points. Noise from various sources can further worsen the situation. Therefore investigations are required to identify limitations of possible HL-LHC layouts. The impact of beam-beam effects on the beam dynamics is investigated by virtue of particle tracking simulations. Using the code BeamBeam3D and the strong-strong collision model, simulations including perturbations by noise and LHC's feedback system, an important means to mitigate transverse emittance growth due to coherent beam excitation, were carried out. The impact of numerical noise on the emittance in simulations and the state of the feedback modeling are presented.

TUPPP023	Operation Status of ALBA Synchrotron Light Source	storage-ring, vacuum, emittance, kicker	1659
	M. Pont CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
	ALBA is a 3.0 GeV third generation synchrotron light source which has been commissioned during 2011. From October 2011 up to 7 beamlines are delivering beam for beamline commissioning, 6 from insertion devices and 1 from a bending magnet. Since April 2012 the facility is open to external users. Beam current has been continuously increased and the present stored beam current for users is 200 mA in a multi-bunch filling pattern. Orbit stability is kept at ±1 micron with a slow orbit feedback. The paper will review the operation and performance status of the different subsystems and review also the main objectives for 2012: target current of 400 mA, delivery of 3000 hours of beam to beamlines, testing of a fast orbit feedback system as well as preparations for top-up operation.

TUPPP034	BPM Gains and Beta Function Measurement Using MIA and FPGA BPMs at the APS	betatron, lattice, optics, quadrupole	1686
	C.-X. Wang, G. Decker, H. Shang, C. Yao ANL, Argonne, USA D. Ji IHEP, Beijing, People's Republic of China
	Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The broadband BPM system at the Advanced Photon Source (APS) is being upgraded with FPGA-based beam history modules, which fix problems in the old history modules and increase functionality. Using these new turn-by-turn BPMs and the newly developed real-time feedback system, measurement of BPM gains, beta function and other optics functions are being developed based on model-independent analysis of turn-by-turn data and model fitting, aiming at quasi-real-time and high-accuracy optics measurement. We will discuss our effort, especially experience with strong nonlinearity and wakefields typical of 3rd-generation light sources.

TUPPR028	Recent Improvements in the Orbit Feedback and Ground Motion Mitigation Techniques for CLIC	luminosity, quadrupole, simulation, ground-motion	1876
	J. Snuverink, J. Pfingstner, D. Schulte CERN, Geneva, Switzerland
	The Compact Linear Collider (CLIC) accelerator has strong stability requirements on the position of the beam. In particular, the beam position will be sensitive to ground motion. A number of mitigation techniques have been proposed - quadrupole stabilization and positioning, final doublet stabilization as well as beam based orbit and interaction point (IP) feedback. Integrated studies of the impact of ground motion on the CLIC Main Linac (ML) and Beam Delivery System (BDS) that model the latest hardware designs have been performed. Furthermore, additional imperfections have been introduced and the robustness of this system is discussed in detail. The possibility of using ground motion measurements as an alternative to the quadrupole stabilization is investigated.

TUPPR032	Beam Stability at CTF3	klystron, pick-up, cavity, linac	1888
	T. Persson, P.K. Skowroński CERN, Geneva, Switzerland
	The two beam acceleration tested in CTF3 imposes very tight tolerances on the drive beam stability. A description of the specialized monitoring tool developed to identify the drifts and jitter in the machine is presented. It compares all the relevant signals in an on-line manner for helping the operator to identify drifts or to log data for off-line analysis. The main sources for the drifts of the drive beam were identified and their causes are described. Feedbacks applied to the RF were implemented to reduce the effects. It works by changing the waveform for the pulse compression to compensate for the drifts.

TUPPR034	Beam-based Alignment in CTF3 Test Beam Line	quadrupole, alignment, beam-losses, injection	1894
	G. Sterbini, S. Döbert, R.L. Lillestøl, E. Marín, D. Schulte CERN, Geneva, Switzerland E. Adli University of Oslo, Oslo, Norway
	The CLIC linear collider is based on the two beams acceleration scheme. During acceleration, the drive beam suffers a large increase in its energy spread. In order to efficiently transport such a beam, beam-based alignment techniques together with tight pre-alignment tolerances are crucial. A beam-based steering campaign has been conducted at the Test Beam Line of the CLIC Test Facility to evaluate the performance of several algorithms. In the following we present and discuss the obtained results.

TUPPR083	Kink Instability Suppression with Stochastic Cooling Pickup and Kicker	ion, electron, pick-up, kicker	2017
	Y. Hao, M. Blaskiewicz, V. Litvinenko, V. Ptitsyn 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. The kink instability is one of the major beam dynamics issues of the linac-ring based electron ion collider. This head-tail type instability arises from the oscillation of the electron beam inside the opposing ion beam. It must be suppressed to achieve the desired luminosity. There are various ways to suppress the instability, such as tuning the chromaticity in the ion ring or by a dedicated feedback system of the electron beam position at IP, etc. However, each method has its own limitation. In this paper, we will discuss an alternative opportunity of suppressing the kink instability of the proposed eRHIC at BNL using the existing pickup-kicker system of the stochastic cooling system in RHIC.

WEEPPB011	Analysis of High Field Non-Linear Losses on SRF Surfaces Due to Specific Topographic Roughness	simulation, superconductivity, niobium, SRF	2188
	C. Xu The College of William and Mary, Williamsburg, USA M.J. Kelley, C.E. Reece, C. Xu JLAB, Newport News, Virginia, USA
	Funding: This work is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The high-field performance of SRF cavities will eventually be limited by the realization of fundamental material limits, whether it be Hc1 or Hsh, or some derivative thereof, at which the superconductivity is lost. Before reaching this fundamental field limit at the macro level, it must be encountered at localized, perhaps microscopic, sites of field enhancement due to local topography. If such sites are small enough, they may produce thermally stabilized normal-conducting regions which contribute non-linear losses when viewed from the macro resonant field perspective, and thus produce degradation in Q0. We have undertaken a calculation of local surface magnetic field enhancement from specific fine topographic structure by conformal mapping method and numerically. A solution of the resulting normal conducting volume has been derived and the corresponding RF ohmic loss simulated.

WEPPC006	CW and LP Operation Test of XFEL-Like Cryomodule	HOM, cryomodule, cavity, cryogenics	2215
	J.K. Sekutowicz, V. Ayvazyan, M. Ebert, J. Eschke, A. Gössel, D. Kostin, I.M. Kudla, W. Merz, F. Mittag, R. Onken DESY, Hamburg, Germany W. Cichalewski, W. Jałmużna, K.P. Przygoda TUL-DMCS, Łódź, Poland K. Czuba, L. Zembala Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland J. Szewiński The Andrzej Soltan Institute for Nuclear Studies, Centre Świerk, Świerk/Otwock, Poland
	A continuous improvement in the performance of superconducting TESLA cavities will make possible, from the cryogenic point of view, operation of the XFEL linac in continuous wave (cw) mode at gradients up to 7.5 MV/m and in long pulse (lp) mode up to nominal gradient of 23.4 MV/m. Each of these new operation modes will offer an additional flexibility in time structure of the photon beam, and therefore will allow for more experiments and in some cases less demanding and less expensive equipment. In this contribution we discuss results of the first RF test of these new types of operation with a XFEL-like cryomodule.

WEPPC017	Design of a High-Speed Pulsed 324MHz Solid-State Amplifier for Use in a Beam Chopper	resonance, impedance, proton, insertion	2242
	S.C. Dillon, B.S. Nobel, C.P. Schach Tomco Technologies, Stepney, South Australia, Australia
	A 324MHz 30kW high-speed pulsed solid-state amplifier has been designed for use in a beam chopper at the Japan Proton Accelerator Complex (J-PARC). This paper discusses the various design challenges and presents the initial performance test results. In particular, the amplifier achieves pulse rise and fall times of less than 15 nanoseconds, is easily upgradeable in power, and withstands 100% power reflection without damage.

WEPPC081	Measurement of the Mechanical Properties of Superconducting Cavities During Operation	cavity, resonance, linac, simulation	2399
	S. Posen, M. Liepe CLASSE, Ithaca, New York, USA
	The Horizontal Test Cryostat (HTC) contains the first prototype 7-cell 1.3 GHz superconducting cavity for the Cornell ERL main linac. In this paper, experimental measurements of the cavity's mechanical properties are presented. The mechanical resonances were studied using a Dynamic Signal Analyzer, which measured the transfer function from the fast piezo tuner to itself and the cavity frequency. The microphonics detuning of the cavity was measured, and found to satisfy the specification that the maximum detuning be below 20 Hz, even without feedback from the piezos. Correlations were studied between the microphonics detuning and the helium pressure, piezo sense signal, and the ground vibrations. The Lorentz force detuning (LFD) coefficient was also measured. The frequencies of the mechanical resonances were compared to simulation. In addition, the performance of the frequency tuners was evaluated. Both the mechanical tuner and the piezo were found to be highly linear with very little hysteresis even on small scales.

WEPPD041	The Strategy between High Precision Temperature Control and Energy Saving for Air-Conditioning System	controls, monitoring, photon, target	2603
	Z.-D. Tsai, W.S. Chan, J.-C. Chang, C.S. Chen, Y.-C. Chung, C.W. Hsu, C.Y. Liu NSRRC, Hsinchu, Taiwan
	In the Taiwan Light Source (TLS), several studies related to the temperature stability for air conditioning system continued to be in progress. Using new control philosophy can minimize temperature variations effectively. A high precision temperature control within ±0.05°C for air condition system has been conducted to meet the more critical stability requirement. Due to the importance of energy saving issue, the power consumption of air conditioning system was also upgraded and intended to reduce extensively. The paper addresses some experience between high precision temperature control and energy saving about operation of air conditioning system. The significant improvements proven that both targets can achieve simultaneously.

WEPPD048	Laser Synchronization at REGAE using Phase Detection at an Intermediate Frequency	laser, electron, controls, LLRF	2624
	M. Felber, M. Hoffmann, U. Mavrič, H. Schlarb, S. Schulz DESY, Hamburg, Germany W. Jałmużna TUL-DMCS, Łódź, Poland
	A new linear accelerator is being set up for electron diffraction experiments at DESY. This machine, called REGAE (Relativistic Electron Gun for Atomic Exploration) is composed of a photo-cathode gun and a buncher cavity. It uses a single laser system for both, the generation of the electron bunches and for pump-probe experiments. The required timing jitter between the electron bunches and the laser pulses at the experiment is in the order of 10 fs rms. The conventional method for laser synchronization using RF technique to measure phase-jitter in the baseband is susceptible to distortions caused by ground-loops and electro-magnetic interference. At REGAE a new scheme for an RF-based laser synchronization is deployed. It uses a down-converter which mixes a higher harmonic of the laser repetition rate down to an intermediate frequency (IF). The IF is digitized and its phase calculated. This information is used for the feedback controller keeping the laser and the RF synchronized.

WEPPD074	Issues and Feasibility Demonstration of Positioning Closed Loop Control for the CLIC Supporting System Using a Test Mock-up with Five Degrees of Freedom	alignment, controls, collider, linear-collider	2696
	M. Sosin, M. Anastasopoulos, N. Chritin, J. Kemppinen, H. Mainaud Durand, V. Rude, G. Sterbini, S. griffet CERN, Geneva, Switzerland
	Since several years, CERN is studying the feasibility of building a high energy e⁺ e⁻ linear collider: the CLIC (Compact LInear Collider). One of the challenges of such a collider is the pre-alignment precision and accuracy requirement on the transverse positions of the linac components, which is typically 14 μm over a window of 200 m. To ensure the possibility of positioning within such tight constraints, CERN Beams Department’s Survey team has worked intensively at developing the methods and technology needed to achieve that objective. This paper describes activities which were performed on a test bench (mock-up) with five degrees of freedom (DOF) for the qualification of control algorithms for the CLIC supporting system active-pre-alignment. Present understanding, lessons learned (“know how”), issues of sensors noise and mechanical components nonlinearities are presented.

WEPPP059	First Measurements with Multibunch Feedback Systems at the Fast Ramping Stretcher Ring ELSA	kicker, damping, cavity, electron	2840
	M. Schedler, F. Frommberger, N. Heurich, W. Hillert, A. Roth, R. Zimmermann ELSA, Bonn, Germany
	Funding: Supported by German Research Foundation through SFB/TR 16. At the Electron Stretcher Facility ELSA of Bonn University, an upgrade of the maximum stored beam current from 20 mA to 200 mA is planned. The storage ring operates applying a fast energy ramp of 4 GeV/s from 1.2 GeV to 3.5 GeV. The intended upgrade is mainly limited due to the excitation of multibunch instabilities. As a countermeasure, we succesfully commissioned state-of-the-art bunch by bunch feedback systems in the longitudinal and the two transverse dimensions. First results concerning the commissioning of the systems as well as the operation during the fast energy ramp will be presented. In particular, the performance while controlling the motion of every single bunch, especially in controlled bunch cleaning, will be discussed.

WEPPP060	A Robust Transverse Feedback System	kicker, status, optics, pick-up	2843
	M. Alhumaidi, A.M. Zoubir TU Darmstadt, Darmstadt, Germany
	Transverse feedback systems use pickups signals to measure the beam instabilities and kickers to correct the beam. The correction signal is calculated according to the transfer matrices between the pickups and the kickers. However, errors due to magnetic field imperfections and magnets misalignments lead to deviations in the transfer matrices from their nominal values, which affects the feedback quality in a negative manner. In this work we address a new concept for robust feedback system against optics errors or uncertainties. A kicker and multiple pickups are used for each transversal direction. We introduce perturbation terms to the transfer matrices between the kicker and the pickups. Consequently, the Extended Kalman Filter is used to estimate the feedback signal and the perturbation terms by means of the measurements from the pickups. Finally results for the heavy ions synchrotron SIS 18 at the GSI are shown.

WEPPP062	Characterization and Stabilization of Multi-Bunch Instabilities at the ANKA Storage Ring	kicker, storage-ring, injection, controls	2849
	E. Huttel FZK, Karlsruhe, Germany N. Hiller, E. Huttel, V. Judin, B. Kehrer, S. Marsching, A.-S. Müller, N.J. Smale KIT, Karlsruhe, Germany
	ANKA is a 2.5 GeV storage ring for synchrotron radiation. Up to 200 mA are accumulated at 0.5 GeV and then ramped to 2.5 GeV. In the past storage ring operation suffered from vertical multi-bunch instabilities. These could partially be cured by increased chromaticity, a large gap in the filling structure and by keeping the beam longitudinally unstable. A vertical digital bunch-by-bunch system from ITECH has been installed that allows an operation of the storage ring without exciting the longitudinal modes. In addition, the system allows analyzing multi-bunch instabilities both transverse and longitudinal and their dependence from cavity temperature, filling structure and chromaticity. This paper reports on our experience operating this system and presents an investigation of multi-bunch modes in the ANKA storage ring.

WEPPP065	Status of the SSRF Fast Orbit Feedback System	controls, storage-ring, electron, insertion	2855
	B.C. Jiang, J. Hou, C.X. Yin, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	The fast orbit feedback system with bandwidth up to 100Hz is under commissioning at SSRF. The main purposes of the system are to suppress the short term orbit stability under sub-micron level and to compensate the orbit distortions caused by changing gaps of the insertion devices. The layout of the system is described and the preliminary commissioning results are given out in this paper.

WEPPP066	Performance Simulations of a Phase Stabilization System Prototype for CTF3	kicker, simulation, collider, linac	2858
	A. Gerbershagen, T. Persson, D. Schulte, P.K. Skowroński CERN, Geneva, Switzerland P. Burrows, G.B. Christian Oxford University, Physics Department, Oxford, Oxon, United Kingdom A. Gerbershagen, C. Perry JAI, Oxford, United Kingdom E. Ikarios National Technical University of Athens, Athens, Greece
	The CLIC drive beam provides RF power for acceleration of the main beam, and hence the drive beam’s longitudinal phase tolerances are very tight. A feedforward chicane consisting of four electromagnetic kickers is proposed as a correction system for the phase errors, which should allow loosening of the tolerances. A prototype of such a chicane system, developed by CERN, INFN and the University of Oxford, is planned to be installed at CFT3 in 2012. The present paper summarizes the parameters of the planned phase correction system and presents simulations, which are used to make predictions of the performance of such a feedforward system at CTF3.

WEPPP067	Commissioning Results of Slow Orbit Feedback using PID Controller Method for the Siam Photon Source	controls, photon, storage-ring, LabView	2861
	S. Klinkhieo, S. Boonsuya, P. Klysubun, S. Krainara, P. Songsiriritthigul, P. Sudmuang, N. Suradet SLRI, Nakhon Ratchasima, Thailand S. Rujirawat Suranaree University of Technology, Nakhon Ratchasima, Thailand
	A slow orbit feedback (SOFB) system has been developed to improve the orbit stability for the storage ring of the Siam Photon Source (SPS). The SOFB uses a PID controller method utilizing LabVIEW channel to access 20 BPMs and 28 correctors of the storage ring. The first phase implementation of the feedback loops based on this method was operated at 0.05Hz of sampling frequency, which reduce the fluctuation of both horizontal and vertical positions of the orbit from ~200 microns down to ~30 microns. The commissioning results indicate that further work and hardware upgrade are required. A higher sampling frequency at least 30Hz is strongly required for PID controller implementation. Upgrading of the existing 12-bit resolution corrector power supplies is also necessary. The basic principle of PID algorithms, hardware, software and commissioning results of the current SOBF system, as well as a future development plan, will be presented.

WEPPP068	Latest Performance Results from the FONT5 Intra-train Beam Position and Angle Feedback System at ATF2	kicker, extraction, linear-collider, collider	2864
	D.R. Bett, R. Apsimon, N. Blaskovic Kraljevic, P. Burrows, G.B. Christian, M.R. Davis, A. Gerbershagen, C. Perry JAI, Oxford, United Kingdom B. Constance 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 time scales, 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. The latest results from beam tests at ATF2 will be presented, including the system latency and correction performance.

WEPPP069	Performance Enhancements for the Transverse Feedback System at the Advanced Photon Source	EPICS, storage-ring, photon, controls	2867
	N.P. Di Monte, R.I. Farnsworth, A.J. Scaminaci ANL, Argonne, USA
	With the success of the transverse feedback system at the Advanced Photon Source (APS), an upgrade to this system is being developed. The current system is operating at a third of the storage ring bunch capacity, or 324 of the available 1296 bunches. This upgrade will allow the sampling of all 1296 bunches and make corrections for all selected bunches in a single storage ring turn. To facilitate this upgrade, a new analog I/O board capable of 352-MHz operation is being developed along with a P0 bunch cleaning circuit. The clock cleaning circuit is also needed for the high speed analog output circuit, which is transmitted about 200 m to a separate DAC unit in real time. This remote DAC will have its transceiver data rate triple from 2.3 Gb to about 7 Gb on a fiber optic link. This paper will discuss some of the challenges in reducing the clock jitter from the system P0 bunch clock along with the necessary FPGA hardware upgrades and algorithm changes, all of which are required for the success of this upgrade.

WEPPP070	Simulation of the APS Storage Ring Orbit Real-Time Feedback System Upgrade Using MATLAB	storage-ring, simulation, controls, dipole	2870
	S. Xu, G. Decker, R.I. Farnsworth, F. Lenkszus, H. Shang, X. Sun ANL, Argonne, USA
	Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source (APS) storage ring orbit real-time feedback (RTFB) system plays an important role in stabilizing the orbit of the stored beam. An upgrade is planned that will improve beam stability by increasing the correction bandwidth to 200 Hz or higher. To achieve this, the number of available steering correctors and beam position monitors (BPMs) will be increased, and the sample rate will be increased by an order of magnitude. An additional benefit will be the replacement of aging components. Simulations have been performed to quantify the effects of different system configurations on performance.

WEPPP071	Phase Noise Studies at the Advanced Photon Source	simulation, storage-ring, synchrotron, photon	2873
	N. Sereno, G. Decker, R.M. Lill, B.X. Yang ANL, Argonne, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Phase noise generated primarily by power line harmonics modulating the 352-MHz rf system in the APS storage ring is a dominant source of high- frequency beam motion, both longitudinally and transversely, due to dispersion in the lattice. It also places fundamental limits on the ability to generate picosecond-scale x-ray pulses for fast pump / probe experiments. Measurements using turn-by-turn beam position monitors (BPMs) located at high-dispersion locations are compared and contrasted with results from a dedicated S-band phase detector connected to either a capacitive pickup electrode or a diamond x-ray detector. Horizontal beam position at high-dispersion locations is related directly to beam phase by a very simple relation involving the momentum compaction. Simulation results are used to validate this relationship and to quantify the relation between phase noise on the main rf vs beam arrival time jitter. A. Zholents et al., NIM A 425, 385 (1999).

WEPPP073	Dynamic Feedback Model for High Repetition Rate Linac-driven FELs	linac, FEL, cavity, beam-loading	2879
	J.M. Byrd, L.R. Doolittle, P. Emma, G. Huang, A. Ratti, C. Serrano LBNL, Berkeley, California, USA
	Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. One of the concepts for the next generation of linac-driven FELs is a cw superconducting linac driving an electron beam with MHz repetition rates. One of the challenges for next generation FELs is improve the shot-to-shot stability of the energy, charge, peak current, and timing jitter of the electron beam. The use of a cw RF system with MHz beam repetition rates presents an opportunity to use broadband feedback to stabilize the beam parameters. To understand the performance of such a feedback system, we are are developing a dynamic feedback model of the machine with a focus on the longitudinal beam properties. The model is being developed as an extension of the LITrack code and will include the dynamics of the beam-cavity interaction, RF feedback, beam-based feedback, and multibunch effects. In this paper, we will present the status of this model along with results.

WEPPP074	Study of a Wideband Feedback Kicker for the SPS	kicker, impedance, cavity, simulation	2882
	S. De Santis, Z. Paret, A. Ratti LBNL, Berkeley, California, USA A. Gallo, F. Marcellini INFN/LNF, Frascati (Roma), Italy
	Funding: Work supported by the US Department of Energy under Contracts DE-AC02-05CH11231 and DE-AC02-76SF00515, and through the US LHC Accelerator Research Program (LARP). The LHC luminosity upgrade currently being planned at CERN depends in large measure on a successful upgrade of its injectors chain. In particular the storing of higher currents in the SPS presents a significant challenge from the point of view of the beam stability. Electron cloud driven and transverse mode-coupled instabilities can disrupt the stored beam to the point of making injection in the LHC impossible. These types of instabilities are characterized by fast growth times and substantial spectral components at high frequency. Therefore a key aspect of any feedback system capable of effectively controlling the instability growth is the development of a suitable kicker with a high frequency response. In this paper we investigate the technologies available for such a kicker and identify a possible solution to be implemented on the SPS. By combining a lower frequency stripline kicker with a high frequency module, such as a damped cavity or a slotted waveguide, it would be possible to provide shunt impedances around 1000 Ω on a bandwidth from DC to 1 GHz. The basic parameters and limits of such a solution are discussed.

WEPPP076	Analysis of Numerical Noise in Particle-In-Cell Simulations of Single-Bunch Transverse Instabilities and Feedback in the CERN SPS	simulation, emittance, pick-up, kicker	2888
	R. Secondo, J.-L. Vay, M. Venturini LBNL, Berkeley, California, USA
	Funding: Work supported by the US-DOE and the US-LHC Accelerator Research Program LARP under Contract DE-AC02-05CH11231. Used resources of NERSC and the Lawrencium cluster at LBNL The operation at high current of the SPS at CERN is limited by transverse Single-Bunch instabilities generated by the effect of electron clouds. A model of a high bandwidth feedback control system has been implemented in the macro-particle code WARP to study bunch dynamics and identify system requirements for the efficient damping of single-bunch transverse instability. We analyze the effect of numerical noise and choice of simulation parameters on the modeling of beam dynamics, focusing in particular on the investigation of the feedback system requirements of minimum power to damp the instability and frequency bandwidth given a fixed gain. We report on simulation results and discuss the plans for the future improvements of the feedback model.

WEPPP077	Control of RF Transients in Cavities Induced by Pulsed High Current Beams	cavity, SRF, controls, linac	2891
	F. Löhl, J. Dobbins, R.P.K. Kaplan, C.R. Strohman CLASSE, Ithaca, New York, USA
	Funding: Supported by NSF award DMR-0807731. The Cornell ERL prototype injector is operated either in a cw or in a pulsed mode. In the latter case, the bunch trains, which have a duration of 100 ns to 10 microseconds and a beam current of up to 100 mA, generate transients in the RF cavity fields which severely distort the beam quality and cause beam loss. In this paper, we present a scheme we use to correct the fast transients based on an adaptive feed-forward method.

WEPPP078	Status of the Mixed-signal Active Feedback Damper System for Controlling Electron-proton Instabilities for the Spallation Neutron Source	pick-up, damping, kicker, proton	2894
	Z.P. Xie, M.J. Schulte UW-Madison, Madison, Wisconsin, USA C. Deibele ORNL, Oak Ridge, Tennessee, USA
	Funding: Work supported by Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy As the beam intensity at the Spallation Neutron Source (SNS) in Oak Ridge National Laboratory (ORNL) is leveled up, it becomes necessary to have greater control over the electron-proton (e-p) instability. This paper presents an updated design of a mixed-signal transverse feedback system for active damping of the e-p instability. It describes the design, features and results of this feedback damper and reviews several experimental studies to understand the system performance and its limitations. The updated mixed-signal feedback damper system employs power amplifiers (PAs), analog-to-digital converters (ADCs), multiple field programmable gate array (FPGA) chips, and digital-to-analog converters (DACs) to provide feedback damping and system monitoring. Unlike existing analog damping systems, FPGA-based feedback damping systems offer programmability while maintaining high performance. The system gain, delay and digital signal processing components can be programmed during the fly to perform timing adjustments, correct for ring harmonics, and equalize magnitude and phase dispersions.

WEPPP083	Near Real-time Response Matrix Calibration for 10-Hz GOFB	dipole, damping, injection, quadrupole	2903
	C. Liu, R.L. Hulsart, A. Marusic, K. Mernick, 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. The 10-Hz global orbit feedback, for damping the trajectory perturbation (~10 Hz) due to the vibrations of the triplets, is operational for injection and store in RHIC. The operation of the system has been performed using transfer functions between the beam position monitors and correctors obtained from the online optics model and a correction algorithm based on singular value decomposition (SVD). Calibration of the transfer functions by measuring the beam position oscillations while modulating the dedicated correctors has been carried out. The feedback results with model matrix and measured matrix will be compared.

WEPPP084	Weighted SVD Algorithm for Close-Orbit Correction and 10 Hz Feedback in RHIC	electron, proton, closed-orbit, ion	2906
	C. Liu, R.L. Hulsart, A. Marusic, R.J. Michnoff, M.G. Minty, V. Ptitsyn 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. Measurements of the beam position along an accelerator are typically treated equally using standard SVD-based orbit correction algorithms so distributing the residual errors, modulo the local beta function, equally at the measurement locations. However, sometimes a more stable orbit at select locations is desirable. In this paper, we introduce an algorithm for weighting the beam position measurements to achieve a more stable local orbit. The results of its application to close-orbit correction and 10-Hz orbit feedback will be shown and analyzed.

WEPPP089	Study of the Combined Controller for Adjusting and Locking a Girder with Micrometer-level at NSRRC	controls, monitoring, storage-ring, synchrotron	2921
	H.S. Wang, M.L. Chen, W.Y. Lai, S.Y. Perng, Y.L. Tsai, T.C. Tseng NSRRC, Hsinchu, Taiwan J.-R. Chen NTHU, Hsinchu, Taiwan
	A girder control system is proposed to quickly and precisely adjust the displacement and rotating angle of all girders in the storage ring with little manpower at the Taiwan Photon Source (TPS) project at National Synchrotron Research Center (NSRRC). In this control girder system, six motorized cam movers supporting a girder are driven on three pedestals to perform six-axis adjustments of a girder. To increase the nature frequency of a girder, the locking system is applied to promote the stiffness of a girder structure. The locking system consists of six locking mechanisms attached to three inboard pedestals and a locking controller. The study of the girder control system and the locking system control combined are achieving to the positioning with micrometre-level. This paper presents details of the study and tests of the combined controller.

WEPPP090	Stable RF Distribution System for the S-band Linac	controls, linac, klystron, extraction	2924
	T. Naito, K. Ebihara, S. Nozawa, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan M. Amemiya AIST, Tsukuba, Japan
	The phase stabilization of the RF phase is key issue for the stable linac operation. An RF distribution system with femto-second stability has been developed for S-band linac using optic fiber links. The system uses a phase stabilized optical fiber (PSOF) and an active fiber length stabilization.* The phase stability is 0.1 degree (100f s) for 24 hours observation. In this paper, we present the test results of the system stability and evaluation of the existing RF reference line by using this system. * Naito et. al. IPAC10 MOPC146

WEPPR049	The Impact of Fill Patterns on the Fast Ion Instability in the ILC Damping Ring	ion, damping, emittance, electron	3036
	G.X. Xia MPI-P, München, Germany
	The ions produced via collisional ionization of the residual gas molecules in vacuum pipe with the circulating electron beam have deleterious effect on the beam properties and may become a limiting factor in the machine’s performance. In this paper, the various beam fill patterns are investigated and their effects on the fast ion instability are discussed. The simulations show that an optimal fill pattern can reduce growth rate of the fast ion instability significantly.

WEPPR058	The Vertical Impedance Distribution Measurement Using Response Matrix Method at BEPCII BPR	impedance, kicker, injection, betatron	3057
	Y. Wei, D. Ji IHEP, Beijing, People's Republic of China
	Funding: Work supported by the Chinese National Foundation of Natural Sciences, contract 111100512108. In the last run of BEPCII, the single bunch current is limited to about 8mA by the beam-beam effect. To obtain the design luminosity, larger number of bunches are necessary. But higher total current may be limited by the collective effects. A good understanding of the transverse impedance distribution around the BEPCII storage ring is required. Response matrix method has been applied successfully in BEPCII to fit the quadrupole errors and restore the optics. We can also calculate the variation of betatron phase advance around the ring with different single bunch current using the response matrix method and the transverse impedance distribution is thus deduced. In this paper, the first measurement of transverse impedance in BEPCII is presented.

WEPPR069	Measurements and Simulations of Transverse Coupled-Bunch Instability Rise Times in the LHC	simulation, injection, octupole, impedance	3087
	N. Mounet, R. Alemany-Fernandez, W. Höfle, D. Jacquet, V. Kain, E. Métral, L. Ponce, S. Redaelli, G. Rumolo, R. Suykerbuyk, D. Valuch CERN, Geneva, Switzerland
	In the current configuration of the LHC, multibunch instabilities due to the beam-coupling impedance would be in principle a critical limitation if they were not damped by the transverse feedback. For the future operation of the machine, in particular at higher bunch intensities and/or higher number of bunches, one needs to make sure the coupled-bunch instability rise times are still manageable by the feedback system. Therefore, in May 2011 experiments were performed to measure those rise times and compare them with the results obtained from the LHC impedance model and the HEADTAIL wake fields simulation code. At injection energy, agreement turns out to be very good, while a larger discrepancy appears at top energy.

WEPPR084	Measurement of Coherent Damping Rate of the APS Storage Ring	damping, kicker, storage-ring, pick-up	3126
	C. Yao, K.C. Harkay, H. Shang, C.-X. Wang ANL, Argonne, USA
	Funding: Work supported by U.S. Department of Energy, Offices of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The APS storage ring is a 7-GeV electron storage ring with a single-bunch current of up to 16 mA during normal user operations. To overcome beam instability we employ both chromatic correction and bunch-by- bunch feedback system. Typically we run a chromaticity of 4 for a 24-single fill pattern and 9 for a hybrids fill pattern in both planes with the feedback system loops closed. The APS upgrade (APS-U) calls for a beam current of 150 mA and installation of vertical deflecting cavities for short X-ray (SPX) production. In order to estimate whether the current chromatic correction and feedback system are adequate for the upgrade, we performed coherent damping rate measurements with two methods: kicking the beam with a kicker pulse and exciting the beam with the feedback system. We conclude that with a chromaticity of 4 in both planes, we can achieve a damping rate of 3 kHz in the x- plane and 2 kHz in the y-plane with feedback loops closed. Similar damping rates can also be achieved with chromatic correction alone. A special fitting program was developed to perform the damping rate analysis. This report presents the measurement data and results of the analysis.

WEPPR087	Dependence of Beam Instabilities Caused by Electron Clouds at CesrTA Due to Variations in Chromaticity, Bunch Current and Train Length	betatron, electron, emittance, positron	3135
	M.G. Billing, G. Dugan, M.J. Forster, D.L. Kreinick, R.E. Meller, M.A. Palmer, G. Ramirez, M.C. Rendina, N.T. Rider, J.P. Sikora, K.G. Sonnad, H.A. Williams CLASSE, Ithaca, New York, USA J.Y. Chu CMU, Pittsburgh, Pennsylvania, USA J.W. Flanagan KEK, Ibaraki, Japan R. Holtzapple, M. Randazzo CalPoly, San Luis Obispo, California, USA
	Funding: Work supported by DOE Award DE-FC02-08ER41538, NSF Award PHY-0734867 and the Lepton Collider R&D Coop Agreement: NSF Award PHY-1002467. Electron cloud-induced beam dynamics is being studied at CESRTA under various conditions. These measurements detect the the coherent self-excited spectrum for each bunch within a train and bunch-by-bunch beam size. In the position spectrum coherent betatron dipole and head-tail motion is detectable for each individual bunch within the train with a sensitivity for the motion of 1.1 (2) microns-rms in the vertical (horizontal) direction for a 1 mA bunch current. These techniques are utilized to study the electron cloud-related interactions, which cause the growth of coherent motion and beam size along the train. We report on the observations and results from studies of the instability growth vs. changes in chromaticity, the current per bunch and the length of the train.

WEPPR090	A 4.2 GS/s Synchronized Vertical Excitation System for SPS Studies - Steps Toward Wideband Feedback	controls, kicker, injection, acceleration	3144
	J.D. Fox, J.J. Olsen, C.H. Rivetta, I.I. Rivetta, O. Turgut, S. Uemura SLAC, Menlo Park, California, USA W. Höfle, 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). A 4.2 GS/s beam excitation system with accelerator synchronization and power stages is described. The system is capable of playing unique samples (32 samples/bunch) for 15,000 turns on selected bunch(es) in the SPS in synchronism with the injection and acceleration cycle. The purpose of the system is to excite internal modes of single-bunch vertical motion, and study the bunch dynamics in the presence of developing Electron cloud or TMCI effects. The system includes a synchronized master oscillator, SPS timing functions, an FPGA based arbitrary waveform generator, 4.2 GS/sec. D/A system and four 80W 20 -1000 MHz amplifiers driving a tapered stripline pickup/kicker. A software GUI allows specification of various modulation signals and selection of bunches and turns to excite, while a remote control interface allows simple control/monitoring of the RF power stages located in the tunnel. Excitation signals developed to excite head-tail and other modes of vertical motion are illustrated. The successful use of this system for SPS MD measurements in August and November 2011 is a vital proof-of-principle for wideband feedback using similar functions to correct the beam motion.

WEPPR091	Multi-Particle Simulation Codes Implementation to Include Models of a Novel Single-bunch Feedback System and Intra-beam Scattering	emittance, simulation, electron, damping	3147
	M.T.F. Pivi, A. Chao, C.H. Rivetta SLAC, Menlo Park, California, USA F. Antoniou, K.S.B. Li, Y. Papaphilippou CERN, Geneva, Switzerland M. Boscolo, T. Demma INFN/LNF, Frascati (Roma), Italy K.G. Sonnad CLASSE, Ithaca, New York, USA
	Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP). The beam tracking codes C-MAD and HEAD-TAIL have been enhanced to include a detailed model of a single-bunch feedback system. Such a system is under development to mitigate the electron cloud and the transverse mode coupling instability (TMCI) in the SPS and LHC at CERN. This paper presents the model of the feedback sub-systems: receiver, processing channel, filter, amplifier and kicker, which takes into account the frequency response, noise, mismatching and technological limits. With a realistic model of the hardware, it is possible to study the prototypes installed in the SPS and design a novel feedback system. The C-MAD code, which is parallel and optimized for speed, now also includes radiation damping and quantum excitation and a detailed model of Intra-Beam Scattering (IBS) based on the Zenkevich-Bolshakov algorithm, to investigate the IBS during damping and its effect on the beam distribution, especially the beam tails, that analytical methods cannot investigate. Intra-beam scattering is a limiting factor for ultra-low emittance rings such as CLIC and Super-B.

THEPPB014	LLRF Testing of Superconducting Cryomodules for the European XFEL	cavity, cryomodule, LLRF, controls	3263
	J. Branlard, V. Ayvazyan, T. Jeżyński, H. Schlarb DESY, Hamburg, Germany W. Cichalewski, W. Jałmużna, A. Piotrowski TUL-DMCS, Łódź, Poland
	During the installation phase of the European XFEL (2014), an average of one superconducting cryomodule per week will be tested and validated before being installed into the XFEL tunnel. Extensive tests will be carried in order to assess the RF performance of each cryomodule. A series of low level RF (LLRF) tests are planned as part of this validation phase, and will assess the cryomodule effective operating gradient, tuning range, compensation of Lorentz force detuning and microphonic behavior. These tests will be carried at DESY, in the Cryomodule Test Bench (CMTB) during the early stage of cryomodule production, and later at the Accelerating Module Test Facility (AMTF). Due to the pace and quantity of the modules to be tested, these tests have to be fully automated. This contribution presents the LLRF tests for the XFEL cryomodule validation, the challenges associated with automation, along with the first experimental results obtained on pre-series cryomodules tested at CMTB.

THPPC056	Development of 12kW RF Power Supply for CYCHU-10 Cyclotron	power-supply, cavity, cyclotron, impedance	3416
	D. Li, T. Hu, J. Huang, K.F. Liu, B. Qin, J. Yang, L. Yang Huazhong University of Science and Technology (HUST), Wuhan, People's Republic of China
	One 12kW RF power supply has been developed for CYCHU-10, which is a 10 MeV cyclotron developed in Huazhong University of Science and Technology (HUST). A high performance DDS chip AD9859 is used to synthesize RF signal in this power supply, which is easy to change the output frequency. The centre frequency is 101MHz, and the frequency bandwidth is more than 1MHz. The RF power supply could operate in fine searching mode, coarse searching mode, tracking mode, and so on. It could search the resonant frequency of cavity with the frequency control loop. The final stage amplifier using a triode 3CW20,000H7 operates in grounded grid configuration, which is stable and reliable. The performance test using a 50Ω resistor load has finished, and major results are shown in this paper.

THPPC063	Commission of RF Power Sources and its Auxiliary Components for TPS in NSRRC	klystron, controls, cavity, synchrotron	3437
	T.-C. Yu, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Y.-H. Lin, C.H. Lo, M.H. Tsai, Ch. Wang, T.-T. Yang, M.-S. Yeh NSRRC, Hsinchu, Taiwan
	Since 2010, before the starting the construction of TPS building in NSRRC, the intensive testing activities for RF facility has begun in RF lab. The RF facility includes 300kW transmitters, 350kW ferrite loads and 350kW circulators with the corresponding LLRF prototype system. Some unexpected situation happened, such as HV weak transformers and loosen greased ferrite tiles during the commission of the 300kW transmitter. Those situation are all encountered during long-term reliability test. For a high availability of beam light in TPS, the highly reliable sub-systems are the basic requirement and hence, long-term reliability is so essential during commission period. Then, the high power circulators for safe RF operation are also tested for various phases change at cavity port. The temperature compensation unit plays key role in proper operation of circulator. Some noticeable test procedure and results would also be introduced as the present RF system progress of TPS plan in NSRRC.

THPPC076	Comparison of LLRF Control Approaches for High Intensity Hadron Synchrotrons: Design and Performance	controls, cavity, beam-loading, synchrotron	3464
	K. Gross, J. Adamy TU Darmstadt, RTR, Darmstadt, Germany
	Funding: Federal Ministry of Education and Research A usual and effective way to realize closed-loop controllers is to use cascaded SISO feedback and to rely on some kind of linear PID structure with parameters adjusted manually in simulations or experiments. Such a control may not reach optimal performance if the system is coupled or non-linear. Regarding intense beams, longitudinal beam loading can be compensated by detuning. But the coupling between phase and amplitude (or I and Q component) highly depends on the tuning, that is on the resonant frequency of the cavity. It is derived that cavity and beam dynamics thus show bi-linear nature, i.e. belong to a well investigated class of non-linear systems with appropriate control strategies available. Different controller designs are compared in terms of performance but also design transparency, the need of previous knowledge like the expected magnitude of beam loading and adaptability to different conditions, e.g. during acceleration or if applied to the full range of ion species as at GSI. The performance evaluation is based on macro-particle tracking simulations. In particular avail and limits of an optimal (quadratic cost) MIMO controller for bi-linear systems are shown. H.K. Khalil: Nonlinear Systems, 3rd Edition, Prentice-Hall, 2002 ** Z. Aganović, Z. Gajić: Linear Optimal Control of Bilinear Systems, Springer-Verlag, 1995.

THPPC079	Prototype Performance of Digital LLRF Control System for SuperKEKB	controls, cavity, LLRF, pick-up	3470
	T. Kobayashi, K. Akai, K. Ebihara, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri KEK, Ibaraki, Japan H. Deguchi, K. Harumatsu, K. Hayashi, J. Nishio, M. Ryoshi Mitsubishi Electric TOKKI Systems, Amagasaki, Hyogo, Japan
	For the SuperKEKB project, a new LLRF control system has been developed to realize high accuracy and flexibility. It is an FPGA-based digital RF feedback control system using 16-bit ADC's, which works on the μTCA platform. In this μTCA-module, the Linux-OS runs then it performs as the EPICS-IOC. This LLRF system is available to both of normal-conducting cavity and super-conducting cavity. A prototype of the LLRF control system for the SuperKEKB was produced. The feedback control stability, temperature characteristics and cavity-tuner control performance are evaluated. The evaluation results and future issue for the operation will be presented in this report. The amplitude and phase stability in the feedback control is 0.03% and 0.02 degrees, respectively. It is sufficiently stable for the SuperKEKB. However, the temperature dependency is not small for the required stability. Its countermeasures are under consideration.

THPPC082	Control Performance Improvement by Using Feedforward in LLRF	controls, klystron, cavity, LLRF	3476
	R. Zeng, D.P. McGinnis, S. Molloy ESS, Lund, Sweden A.J. Johansson Lund University, Lund, Sweden
	The LLRF design is ongoing at ESS (European Spallation Source). One major task of LLRF is to overcome a variety of perturbations such as klystron droop and ripple, Lorentz detuning and beam loading. These perturbations can be well suppressed by classical PI (proportional-integral) controller in feedback loop, but at a cost of raising risk of instability and consuming power overhead for overshoot. Since ESS is a green project focusing on energy efficiency, we will hence investigate in this paper some feedforward and advanced adaptive algorithms to deal with these perturbations, so as to improve the control performance and reduce the power overhead.

THPPC083	Investigation of Feedback Control for Klystron Ripple	cavity, klystron, controls, cathode	3479
	R. Zeng, D.P. McGinnis, S. Molloy ESS, Lund, Sweden A.J. Johansson Lund University, Lund, Sweden
	At ESS (European Spallation Source), there might be potentially serious droop and ripple because of long RF pulse more than 3 ms. It is important for us to know to what extent the droop and ripple affects the klystron output, and how much we can tolerate. The variations of the phase and amplitude of klystron output due to the change in klystron cathode voltage is investigated in this Paper. The mechanism and the effectiveness of the feedback control to suppress the variations are given. To understand the limitation of the feedback, both proportional controller and proportional-integral controller used in feedback loop are simulated and analyzed respectively for superconducting cavity and normal conducting cavity. The tolerances of the droop and ripple in cathode voltage under feedback control are shown according to the data and results obtained.

THPPC084	LHC One-turn Delay Feedback Commissioning	cavity, klystron, LLRF, beam-loading	3482
	T. Mastoridis, P. Baudrenghien, J.C. Molendijk CERN, Geneva, Switzerland
	The 1-turn delay feedback is an FPGA based feedback system part of the LHC cavity controller, which produces gain only around the revolution frequency harmonics. As such, it helps reduce the transient beam loading and effective cavity impedance. Consequently, it increases the stability margin for Longitudinal Coupled Bunch Instabilities driven by the cavity impedance at the fundamental and allows reliable operation at higher beam currents. The 1-turn delay feedback was commissioned on all sixteen cavities in mid-October 2011 and was used in operation for the rest of the run. The commissioning procedure and algorithms for setting-up are presented. The resulting improvements in transient beam loading, beam stability, and required klystron power are analyzed. The commissioning of the 1-turn delay feedback reduced the cavity voltage phase modulation from approximately six degrees peak-to-peak to below one degree at 400 MHz.

THPPC090	Robust Control of a Two-Input Two-Output (TITO) Multistate Cavity RF System ith Mismatched Uncertainty	cavity, controls, simulation, LLRF	3494
	S. Kwon, M.S. Prokop, A. Scheinker LANL, Los Alamos, New Mexico, USA
	A RF cavity is well modeled as a linear two input two output (TITO) system in the Inphase/Quadrature (IQ) coordinates and is both controllable and observable. Whether it is due to the beam loading or Lorentz force detuning of a superconducting cavity, a cavity frequency detuning can be modeled as a matched uncertainty. The cavity field of a TITO cavity system with a matched uncertainty is controlled by output feedback or state feedback, whose error bound is made arbitrary small. Because of the building cost of the RF system, the single RF source (single klystron)-multicavity structure is sometimes used. This structure is described as a two-input multiple-output (TIMO) system. The control problem is not a simple extension of the single TITO system. Though the controllability and observability are preserved, the matched uncertainty of the TITO cavity system caused by cavity detuning becomes a mismatched uncertainty. The error bound of outputs is made arbitrary small by a control, only boundedness of the cavity fields of each TITO subsystem is guaranteed. In this paper, the properties of the TITO and the TIMO cavity RF systems are investigated.

THPPD002	The First Magnetic Field Control (B-Train) to Optimize the Duty Cycle of a Synchrotron in Clinical Operation	controls, synchrotron, extraction, pick-up	3503
	E. Feldmeier, R. Cee, M. Galonska, Th. Haberer, A. Peters, S. Scheloske HIT, Heidelberg, Germany
	In December 2011 the Heidelberg Ion Therapy Center started to use the magnetic field feedback control for its clinical operation. Therewith the magnetic field deviation of the ramped magnets in the synchrotron depending on eddy currents and hysteresis are no longer in effect. Waiting times on the flattop and the "chimney" in the recovery phase of the synchrotron cycle are no longer necessary. The efficiency of the accelerator is increased by more than 20\% and the treatment time shortens accordingly. The core of the magnetic feedback system is a real time measuring system of the magnetic field with extremely high precision.

THPPD014	Design and Performance of Various kinds of Corrector Magnets for the Taiwan Photon Source	booster, vacuum, simulation, power-supply	3524
	C.Y. Kuo, C.-H. Chang, M.-H. Huang, C.-S. Hwang, J.C. Jan, F.-Y. Lin NSRRC, Hsinchu, Taiwan
	Three types of DC corrector magnets will be installed in the booster ring (BR), LINAC to booster (LTB) and booster to storage ring (BTS) in the Taiwan photon source (TPS). These DC corrector magnets have different gap sizes, iron lengths and field strengths for different bending angles to optimize the electron beam. The DC magnetic fields are simulated by TOSCA 2D/3D static field analysis and optimum processes are discussed. An AC steering fast feedback corrector (FFC) combines horizontal and vertical dipole fields for the fast feedback correction in the storage ring (SR). The field variation with the alternating current in the 300Hz frequency of the FFC magnet is simulated by the Opera 3d ELEKTRA/SS analysis module to estimate the operating current. This paper will be presented about features, design concept and results of field measurement of these corrector magnets. NSRRC, 10¹ Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan

THPPD025	Expected and Measured Behaviour of the Tune in the LHC Operation at 3.5 TeV	injection, quadrupole, dipole, betatron	3554
	N. Aquilina CERN, Geneva, Switzerland
	The tune of the Large Hadron Collider depends on the strength of the quadrupole magnets, the b2 component in the main dipoles plus the b3 component in the main dipoles and the sextupolar correctors via feed down in case of systematic misalignment. The magnetic model of the machine, based on a fit of magnetic measurements, has an intrinsic precision which can be estimated in a few units. During the first years of operation of the LHC, tune has been routinely measured and corrected through a feedback system. In this paper we reconstruct from the beam measurements and the settings of the feedback loop the evolution of tune during injection, ramp, and squeeze. This gives the obtained precision of the magnetic model of the machine with respect to quadrupolar and sextupolar components. At the injection plateau there is an unexpected large decay whose origin is not understood: we present the data, with the time constants and the dependence on the previous cycles, and compare to the magnetic measurements. During the ramp the tune drifts by about 0.05: this precision is related to the precision in tracking the quadrupolar field in the machine.

THPPD062	Development of Digital-controlled Corrector Magnet Power Converter with Shunt as a Current Sensing Component	controls, power-supply, simulation	3653
	B.S. Wang, J.C. Huang, K.-B. Liu NSRRC, Hsinchu, Taiwan
	In Taiwan light source (TLS), Bira MCOR power converter modules are adopted as the corrector magnet power converters, the output is regulated by analog PWM IC that caused nonlinear behavior at zero cross and the adjustment of compensator for difference kind of magnet load is inconvenient. In the thesis the analog regulation IC is replaced by a fully digital regulation control circuit to realize digital regulation control converter. With plugging the home-made fully DSP regulation control cards into MCOR30 that the current sensing component is a shunt, the switching losses of MOSFET was reduced and the cost that the component of current sense. With the fully digital regulation control circuit, the parameter of the compensator for different magnet load is very easy to adjustment. In addition, the feasibility and validity of MOSFET switching theorem is simulated with Matlab simulink and the performance of this power converter is verified, the output current ripple of this power converter could be lower than 10ppm, which is beyond the requirement of current TLS corrector power converter and qualified to be used in the future TPS facility.

THPPD064	The Compensator Design of the Fully Digital Controlled Corrector Magnet Power Converter by Using LabView as the Development Tools	controls, LabView, power-supply	3659
	B.S. Wang, J.C. Huang, K.-B. Lin NSRRC, Hsinchu, Taiwan
	The auto-tuning of PI-compensator for power converter is fulfilled by using the LabVIEW. The current error signals of the power converter with different PI compensating parameters are transferred by RS-232 or Ethernet communication interface from DSP card into LabVIEW and FFT analysis are calculated. The FFT analysis are stored in the batch file for further numerical analysis and the parameters with the best response is recognized which will be set as the default PI parameters. In addition, the feasibility and validity of auto-tuning theorem was verified by measuring the long-term stability of output current and during the long-term measuring period the stability and ripple current of the power converter are observed. In this thesis, the fully digital regulation controlled corrector magnet power converter with a shunt as the current sensing component was used as the developing platform. The auto-tuning theorem was realized and applied to the compensator of the power converter, and the best output current response of the power converter was fulfilled.

THPPD066	High Precision Programmable of TPS Quadrupole Magnet Power Supply	controls, power-supply, quadrupole, synchrotron	3662
	Y.S. Wong, J.C. Huang, K.-B. Liu, W.S. Wen NSRRC, Hsinchu, Taiwan
	In 1993, the first of Taiwan light source was held on October 16. First beam stored in the storage ring and facility at synchrotron radiation research centre (SRRC) was opened to users and the full energy injection to 1.5Gev after seven years. In 2007, the president of Executive Yuan Taiwan had been announcement to set up a third-generation synchrotron radiation. Taiwan Photon Source (TPS) project total budget of NT6, 885 million from 2007~ 2013. TPS project will improve technical capability to build to3.3Gev electron energy. Totally had been installed 1032sets of magnet power supplies for the storage ring and 152 sets for the injector. In the future, Taiwan photon source set up complete and operation, it will offer one of the world's brightest synchrotron x-ray sources.

THPPD073	Development and Management of the Modulator System for PLS-II 3.0 GeV Electron Linac	controls, power-supply, linac, klystron	3683
	S.H. Kim, J.Y. Huang, S.J. Kwon, B.-J. Lee, Y.J. Moon, S.H. Nam, S.S. Park, S. Shin PAL, Pohang, Kyungbuk, Republic of Korea
	Funding: This work is supported by MEST(Ministry of Education, Science and Technology) and POSCO(Pohang Steel and Iron Company). The Pohang Accelerator Laboratory (PAL) had started the upgrade project (called PLS-II) of the Pohang Light Source (PLS) from 2009 for increasing its energy from 2.5 GeV to 3 GeV and changing the operation mode from fill-up to top-up mode. Top-up mode operation requires high energy stability of the linac beam and machine reliability in the linac modulator systems. For providing the additional 0.5 GeV energy from the 2.5 GeV PLS linac, we added four units of the modulator system. We have two different types of the pulse modulator system for using existing pulse modulators, thyristor control type, in the upgrade project (PLS-II). The two types are thyristor control type and inverter power type. In the thyristor control type, a de-Qing system controls the modulator pulse forming network (PFN) charging voltage stability, and in the inverter power supply type, CCPS provides highly stable charging voltage to the modulator. We will present development and management of the pulse modulator system for obtaining machine reliability and stability from 3.0 GeV linac.

THPPP010	LHC Orbit Correction Reproducibility and Related Machine Protection	controls, status, luminosity, injection	3746
	K. Fuchsberger, T. Baer, R. Schmidt, J. Wenninger CERN, Geneva, Switzerland
	The Large Hadron Collider (LHC) has an unprecedented nominal stored beam energy of up to 362 MJ per beam. In order to ensure an adequate machine protection by the collimation system, a high reproducibility of the beam position at collimators and special elements like the final focus quadrupoles is essential. This is realized by a combination of manual orbit corrections, feed forward and real time feedback. In order to protect the LHC against inconsistent orbit corrections, which could put the machine in a vulnerable state, a novel software-based interlock system for orbit corrector currents was developed. In this paper, the principle of the new interlock system is described and the reproducibility of the LHC orbit correction is discussed against the background of this system.

THPPP011	Studies on a Wideband, Solid-state Driven RF System for the CERN PS Booster	impedance, cavity, acceleration, booster	3749
	M.M. Paoluzzi, L. Arnaudon, N. Chritin, M. Haase, K. Hanke, B. Mikulec, T. Tardy CERN, Geneva, Switzerland
	In the framework of the LHC Injectors Upgrade project (LIU) the PS Booster (PSB) RF systems will undergo in depth consolidation and upgrade programs. The aim is increasing the extraction energy to 2 GeV and allowing reliable operations during next 25 years. Substantial improvements could come from the replacement of the existing narrowband, tuned systems covering the h=1 and h=2 frequency ranges (0.6 / 1.8 MHz and 1.2 / 3.6 MHz respectively) with wideband (0.5 / 4 MHz) Finemet® loaded cavities. The new system would be modular, allow multi-harmonic operation, use solid-state power stages and include fast RF feedback to compensate beam loading effects to some extent. A prove of principle system providing ≈3.0 kV accelerating voltage has been designed, constructed and installed in one of the PSB rings. This paper provides details on the design and measurements as well as information on the project status.

THPPP047	The ESS Control Box	controls, EPICS, target, neutron	3844
	E. Laface ESS, Lund, Sweden M. Reščič Cosylab, Ljubljana, Slovenia
	The European Spallation Source will be a 5 MW superconducting proton linac, with fixed target, for the production of a stream of neutrons. The entire machine, the target and all the instruments will be controlled by an Integrated Control System: this is a set of hardware and software tools created to provide the most possible easy and flexible interface for the operator daily usage in the control room. The hardware core of the Integrated Control System is the Control Box, a Linux-based computer designed to provide a common platform for the ESS hardware developers. The software front-end for the Control Box is the Experimental Physics and Industrial Control System - EPICS, a standard protocol used to control large facilities such as accelerators or nuclear power plants. In this paper the main characteristics of the Control Box and the EPICS system are presented.

THPPR010	Integrate EPICS System with the TLS Control System	EPICS, controls, synchrotron, status	3984
	Y.-S. Cheng, Y.-T. Chang, J. Chen, P.C. Chiu, K.T. Hsu, K.H. Hu, C.H. Kuo, C.Y. Liao, C.Y. Wu NSRRC, Hsinchu, Taiwan
	The TLS (Taiwan Light Source) is a third generation of synchrotron light source, and it has been operated since 1993. The TLS control system was developed and implemented by ourselves. The control system of our new project (TPS, Taiwan Photon Source) is developed and based upon the EPICS framework. To earn more experiences on the EPICS usage, some of the TLS newly installed subsystem run EPICS directly. For example, BPM system, bunch-by-bunch feedback system, remote oscilloscope waveform access and so on adapt the EPICS interface to control and monitor. The EDM and Matlab (with LabCA) toolkits are used as EPICS graphical user interface, and it is also operated at the TLS control consoles environment normally. The archive system transaction between the TLS control system format and EPICS PVs (Process Variables) has been implemented for user access with the existing archive viewer. The efforts will be described at this report.

THPPR014	FRIB High-level Software Architecture	controls, EPICS, monitoring, optics	3996
	P. Chu, T.D. Brown, R. Gaul, S. Peng FRIB, East Lansing, Michigan, USA E.T. Berryman, V. Vuppala NSCL, East Lansing, Michigan, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 The Facility for Rare Isotope Beams (FRIB) is setting up its high-level application software architecture. The architecture is based on Service Oriented Architecture, and consists of back-end data storage, client/service infrastructure, control system connectivity, supporting libraries and front-end Graphical User Interface (GUI). The architecture provides online models of FRIB as a service and allows for storage of both structured and non-structured data. The model for structured data is implemented using the Integrated Relational Model of Installed Systems (IRMIS). The GUI is based on Control System Studio (CSS) framework. Libraries, service, data access and GUI tools will be available as Application Programming Interface (API) or plug-ins. The infrastructure and technologies chosen here will utilize the robustness and performance for applications, as well as support quick prototyping for physicists. This paper describes FRIB’s high-level application software architecture and some of the current prototypes.

THPPR039	Controlled Transverse Blow-Up of High-energy Proton Beams for Aperture Measurements and Loss Maps	injection, emittance, resonance, proton	4059
	W. Höfle, R.W. Assmann, S. Redaelli, R. Schmidt, D. Valuch, D. Wollmann, M. Zerlauth CERN, Geneva, Switzerland
	A technique was developed to blow-up transversely in a controlled way high energy proton beams in the LHC. The technique is based on band limited white noise excitation that is injected into the transverse damper feedback loop. The injected signal can be gated to selectively blow-up individual trains of bunches. The speed of transverse blow-up can be precisely controlled. This opens the possibility to perform safely and efficiently aperture measurements and loss maps with high intensity bunch trains well above stored beam energies that are considered to be safe. In particular, lengthy procedures for measurements at top energy, otherwise requiring multiple fills of individual bunches, can be avoided. In this paper, the method is presented and results from beam measurements are discussed and compared with alternative blow-up methods.

THPPR040	First Operational Experience with the LHC Machine Protection System when Operating with Beam Energies Beyond the 100 MJ Range	injection, luminosity, monitoring, interlocks	4062
	M. Zerlauth, R.W. Assmann, B. Dehning, M. Ferro-Luzzi, B. Goddard, M. Lamont, R. Schmidt, A.P. Siemko, J.A. Uythoven, J. Wenninger CERN, Geneva, Switzerland
	The LHC made a remarkable progress in luminosity production during 2011 operation. This was made possible by a progressive increase of beam intensities by more than 5 orders of magnitude, reaching stored beam energies beyond 100MJ at the end of the year. The correct functioning of the machine protection systems was vital during initial operation and even more when approaching nominal beam parameters, where an uncontrolled loss of a small fraction of the beam is already sufficient to damage accelerator equipment or the large experimental detectors The machine protection system depends on the interplay of many different elements: beam dumping system, beam interlocks, beam instrumentation, equipment monitoring, collimators and absorbers, etc. The strategy applied during 2011 to allow for an efficient but yet safe increase of the beam intensities is presented along with the associated risks and drawbacks of a too aggressive approach. The experience gained with the key systems will be discussed along with possibilities to further enhance machine availability whilst maintaining the current level of safety.

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MOOAA03

Fast Feedback Strategies for Longitudinal Beam Stabilization

controls, laser, electron, free-electron-laser

26

S. Pfeiffer, M.K. Bock, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany
W. Jałmużna
TUL-DMCS, Łódź, Poland
G. Lichtenberg, H. Werner
TUHH, Hamburg, Germany

The key for pump-probe and seeding experiments at Free Electron Lasers such as FLASH is a femtosecond precise regulation of the bunch arrival time and compression. To maintain this beam based requirements, both for a single bunch and within a bunch train, it is necessary to combine field and beam based feedback loops. We present in this paper an advancement of the currently implemented beam based feedback system at FLASH. The principle of beam based modulation of the RF set point can be superimposed by a direct feedback loop with a beam optimized controller. Recent measurements of the achieved bunch arrival time jitter reduction to 20 fs have shown the performance gain by this direct feedback method *. The combination of both approaches will be presented and possible advantages are discussed.
* C. Schmidt et al., “Feedback Strategies for Bunch Arrival Time Stabilization at FLASH Towards 10 fs,” FEL’2011, Shanghai, August 2011, THPA26, http://www. JACoW.org.

Slides MOOAA03 [0.544 MB]

MOEPPB015

Excitation of Intra-bunch Vertical Motion in the SPS - Implications for Feedback Control of Ecloud and TMCI Instabilities

resonance, pick-up, betatron, synchrotron

112

J.D. Fox, J.M. Cesaratto, M.T.F. Pivi, C.H. Rivetta, O. Turgut, S. Uemura
SLAC, Menlo Park, California, USA
W. Höfle, 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).
Electron cloud and transverse mode coupled-bunch instabilities (TMCI) limit the bunch intensity in the CERN SPS. Intra-bunch fast feedback systems are a possible method to control these effects. This paper presents experimental measurements of single-bunch motion in the SPS driven by a GHz bandwidth vertical excitation system*. The primary goal is to quantify the change in internal bunch dynamics as instability thresholds are approached, and quantify the frequencies of internal modes as Ecloud effects become significant. The beam response is sampled at 20 GS/sec. in response to arbitrary excitation patterns, with data in 2011 taken at 3 bunch intensities. We show the excitation of barycentric, head-tail and higher vertical modes. The beam motion is analyzed in the time domain, via animated presentations of the sampled vertical signals, and in the frequency domain, via spectrograms showing the modal frequencies vs. time. The demonstration of the excitation of selected internal modes is a significant step in development of the feedback control techniques.
* "A 4 GS/Sec. Synchronized Vertical Excitation System for SPS Studies - Steps Towards Wideband Feedback," these proceedings.

MOPPC012

Reliability and Intervention Management for the LHC

controls, radiation, status, site

148

K. Foraz, J.R. Cook, J. Coupard, B. Daudin, J. De Jonghe, F. B. Dos Santos Pedrosa, E.R. Fuentes, C. Garino, K. Golikov, S. Grillot, M.R. Jaekel, P. Sollander
CERN, Geneva, Switzerland

Since 2010, CERN has entered a mode of continuous operation of the LHC and its injectors, which implies the continuous operation of all the infrastructure and support systems. High reliability of the machines is crucial to meet the physics goals. This high reliability must be accompanied by a fast restart after programmed stops. Since 2010, an important effort has been put in place, to ease the coordination process during the programmed stops and to reinforce the management of the interventions (preparation, approval, follow-up, traceability, closure). This paper describes the difficulties from the first year related to this coordination, and the impact on operation. The tools developed for the management of the interventions, their assets and the effect on the reliability of the LHC will also be presented and discussed.

MOPPC015

Proposal for an RF Roadmap Towards Ultimate Intensity in the LHC

cavity, klystron, injection, beam-loading

154

P. Baudrenghien, T. Mastoridis
CERN, Geneva, Switzerland

The LHC is currently operated with 1380 bunches at 50 ns spacing and 1.4 E11 p per bunch (0.35A DC). In this paper the RF operation with ultimate bunch intensity (1.7 E11 p per bunch) and 25 ns spacing (2808 bunches per beam) summing up to 0.86A DC is presented. With the higher beam current, the demanded klystron power will be increased and the longitudinal stability margin reduced. In addition one must consider the impact of a klystron trip (voltage and power transients in the three turns latency before the beam is actually dumped). In this work a scheme is proposed that can deal with ultimate bunch intensity, without modification to the RF power system. Only a minor upgrade of the LLRF will be necessary: the field set point will be modulated according to the phase shift produced by the transient beam loading, thus minimizing the requested RF power while keeping the strong feedback for stability and reduction of RF noise.

MOPPC017

Causes and Solutions for Emittance Blow-Up During the LHC Cycle

emittance, injection, luminosity, proton

160

M. Kuhn
Uni HH, Hamburg, Germany
G. Arduini, B.J. Holzer, J.M. Jowett, V. Kain, F. Roncarolo, M. Schaumann, R. Versteegen, J. Wenninger
CERN, Geneva, Switzerland

Emittance measurements during the run 2011 indicated a blow-up of 20 % to 30 % from LHC injection to collisions. At the LHC design stage the total allowed emittance increase through the cycle was set to 7 %. One of the goals of the 2012 LHC run is therefore to understand and counteract the blow-up. Emittance growth measurements through the LHC cycle along with correlations with possible sources are presented in this paper. Solutions are proposed where possible. The emittance determination accuracy relies on the knowledge of the beam optics and on the present performance of the transverse profile monitors. Possible improvements of the diagnostics and of the related data analysis are also discussed.

MOPPD051

Performance of Resonant Slow Extraction from J-PARC Main Ring

extraction, quadrupole, proton, septum

481

M. Tomizawa, Y. Arakaki, T. Kimura, S. Murasugi, R. Muto, H. Nakagawa, K. Okamura, H. Sato, Y. Shirakabe, T. Toyama, E. Yanaoka, M. Yoshii
KEK, Ibaraki, Japan
D. Horikawa
Sokendai, Ibaraki, Japan
K. Mochiki
Tokyo City University, Tokyo, Japan
A. Schnase
JAEA/J-PARC, Tokai-mura, Japan

Proton beam accelerated by the J-PARC main ring (MR) with an imaginary transition lattice is slowly extracted by a third integer resonant extraction scheme and delivered to the hadron experimental hall. One of the critical issues in the slow extraction from a high intensity proton synchrotron is the inevitable beam loss caused by the extraction process at septum devices. A design with low beam loss (high extraction efficiency) is required to reduce machine damage and radiation exposure during hands-on maintenance. We have designed the slow extraction scheme to obtain high extraction efficiency for the MR lattice. The scheme has a large step size and a small angular spread enabling a hit rate of the beam on the developed thin septum device. Since the first 30 GeV proton beam was successfully delivered to the experimental hall in January 2009, an extremely high extraction efficiency of 99.5% has been achieved by an intensive beam tuning. In this paper, we report details of such performance. We will also describe some schemes to improve the serious spiky spill time structure due to large current ripples from the power supplies for the bending and quadrupole magnets.

MOPPD071

Error Localization in RHIC by Fitting Difference Orbit

storage-ring, closed-orbit, dipole, optics

526

C. Liu, M.G. Minty, V. Ptitsyn
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.
Many errors in an accelerator are evidenced as transverse kicks to the beam, which distort the beam trajectory. Therefore, the information of the errors are imprinted in the distorted orbits, which are different from what would be predicted by the optics model. In this paper, we introduce an algorithm for fitting the orbit based on an on-line optics model. We apply the algorithm to localize the location of the elusive source of vertical diurnal variations observed in RHIC, and analyze D0/Dx errors in local coupling measurement.

MOPPR015

Bunch-by-bunch Feedback Systems at the DELTA Storage Ring

kicker, electron, synchrotron, injection

807

M. Höner, M. Bakr, H. Huck, S. Khan, R. Molo, A. Nowaczyk, A. Schick, P. Ungelenk, M. Zeinalzadeh
DELTA, Dortmund, Germany

Funding: Work supported by BMBF (05K10PEB)
At the DELTA 1.5-GeV electron storage ring operated as a synchrotron radiation source by the TU Dortmund University, bunch-by-bunch feedback systems have been recently installed and commissioned to detect and suppress longitudinal as well as transverse multibunch instabilities. Besides that, the feedback systems are used as a diagnostics tool. Growth rates of multibunch instabilities and their dependence on the beam current have been measured. Additionally, the oscillation amplitudes of electron bunches have been studied during the injection process.

MOPPR021

Commissioning of a New Beam-position Monitoring System at ANKA

booster, controls, brilliance, synchrotron

825

S. Marsching, N. Hiller, E. Huttel, V. Judin, B. Kehrer, M. Klein, C.A.J. Meuter, A.-S. Müller, M.J. Nasse, M. Schuh, N.J. Smale, M. Streichert
KIT, Karlsruhe, Germany
G. Rehm
Diamond, Oxfordshire, United Kingdom

A new beam-position monitoring and diagnostic system is being commissioned at ANKA, the synchrotron light source of the Karlsruhe Institute of Technology. This system is based on 40 Libera Brilliance devices from Instrumentation Technologies. It provides turn-by-turn information about the beam position. This information can be used for beam diagnostics (e.g. finding the position where the beam is lost during injection phase) and can also form the base of a fast orbit-correction scheme. We have performed studies to assess the performance of the new BPM system in comparison to the old system being replaced. In order to optimize the commissioning process we have developed a scheme for switching to the new system gradually by integrating it with the MATLAB Middle-Layer using EPICS control software. In this contribution we present the results of our comparison of the two BPM systems and provide an insight into the experience gained during the commissioning process.

MOPPR032

Electron Beam Diagnostics based on Transverse Feedback System at Duke Storage Ring

storage-ring, electron, monitoring, FEL

849

W. Xu, D.H. He
USTC/NSRL, Hefei, Anhui, People's Republic of China
J.Y. Li, W. Wu, Y.K. Wu
FEL/Duke University, Durham, North Carolina, USA

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
To combat electron beam instabilities, a field programmable gate array (FPGA) based bunch-by-bunch transverse feedback (TFB) has been developed for the Duke storage ring. While it is capable of suppressing transverse beam instabilities for multi-bunch operation, the TFB system has not been needed for typical operation of the Duke storage ring FEL. To explore the great potential of this system, we have focused on the development of TFB based beam diagnostics. A TFB based tune measurement system has been developed using two methods: the tune scan method and tune monitoring method. With the tune monitoring method, a much faster method of the two, we have studied the tune stability of the electron beam in the Duke storage ring. This tune measurement system also allows us to conduct chromaticity measurements more quickly, compared with the existing chromaticity measurement system using a network analyzer. Finally, the TFB based tune system has been used to calibrate the tune knob and chromaticity knob for the Duke storage ring.

MOPPR036

Correlation Analysis of Beam Diagnostic Measurements in SSRF

status, lattice, diagnostics, background

858

Z.C. Chen, Y.B. Leng, Y.B. Yan
SSRF, Shanghai, People's Republic of China
B.P. Wang
SINAP, Shanghai, People's Republic of China

Funding: Supported by National Natural Science Foundation of China (11075198)
Signals from various probes of the beam diagnostic system in Shanghai Synchrotron Radiation Facility (SSRF) were processed with correlation analysis algorithms. The resulting data allowed us to sort the probes by confidence, which means the stable and accurate signals could be separated from the faulty or noisy ones. And the beam dynamics measurements became electronic instrument free at the same time. This makes it possible to eliminate bad Beam Position Monitors (BPM) from the feedback system, offer a more confident set of beam parameters and estimate useful global information by extracting the relationship between some probes.

MOPPR042

Characterization Tests of a Stripline Beam Position Monitor for the CLIC Drive Beam

impedance, quadrupole, extraction, simulation

873

A. Benot-Morell, A. Faus-Golfe, J.J. García-Garrigós
IFIC, Valencia, Spain
A. Benot-Morell, L. Søby
CERN, Geneva, Switzerland
J.M. Nappa, J. Tassan-Viol, S. Vilalte
IN2P3-LAPP, Annecy-le-Vieux, France
S.R. Smith
SLAC, Menlo Park, California, USA

Funding: FPA2010-21456-C02-01, SEIC-2010-00028
A prototype of a stripline Beam Position Monitor (BPM) with its associated readout electronics has been developed at CERN in collaboration with SLAC, LAPP and IFIC. In this paper, the design and simulations of the BPM with the analog readout chain and the BPM test bench are described, and the results of the first characterization tests are presented. The position resolution and accuracy parameters are expected to be below 2μm and 20μm respectively for a beam with a bunching frequency of 12GHz, an average current of 101A and a machine repetition rate of 50Hz.

MOPPR052

Integration Design of BPM and Orbit Feedback Electronic for the TPS

power-supply, controls, EPICS, brilliance

900

C.H. Kuo, P.C. Chiu, K.T. Hsu, K.H. Hu, C.Y. Wu
NSRRC, Hsinchu, Taiwan

TPS (Taiwan Photon Source) is a 3 GeV synchrotron light source which is being in construction at NSRRC. The orbit measurement and control must be precise much than before in the TPS. New BPM electronic design with the latest generation FPGA and new mechanical form factor to enhance functionality of current generation products will be employed for the TPS. The prototype BPM electronics is testing in the TLS. These testing experiences will be applied in the TPS BPM electronic and software modification. To achieve the stringent orbit stability goal of the TPS, orbit feedback system is designed to eliminate beam motions due to various perturbation sources. The new orbit feedback system is merged to BPM electric system. This design will be enhanced to hardware reliability and fast data exchange performance. The design and implementation plan of the BPM system and the orbit feedback system are summarized in this report.

MOPPR064

Development of a Turn-by-Turn Beam Position Monitoring System for Multiple Bunch Operation of the ATF Damping Ring

extraction, damping, synchrotron, monitoring

930

P. Burrows, R. Apsimon, D.R. Bett, N. Blaskovic Kraljevic, G.B. Christian, M.R. Davis, A. Gerbershagen, C. Perry
JAI, Oxford, United Kingdom
B. Constance
CERN, Geneva, Switzerland
J. Resta-López
IFIC, Valencia, Spain

An FPGA-based monitoring system has been developed to study multi-bunch beam instabilities in the damping ring (DR) of the KEK Accelerator Test Facility (ATF). The system utilises a stripline beam position monitor (BPM) and a single-stage down-mixing BPM processor. The system is designed to record the horizontal and/or vertical positions of up to three bunches in the DR with c. 150ns bunch spacing, or the head bunch of up to three trains in a multi-bunch mode with bunch spacing of 5.6 ns. The FPGA firmware and data acquisition software allow the recording of turn-by-turn data. An overview of the system and performance results will be presented.

MOPPR065

A Low-latency Sub-micron Resolution Stripline Beam Position Monitoring System for Single-pass Beamlines

monitoring, linear-collider, extraction, collider

933

P. Burrows, D.R. Bett, N. Blaskovic Kraljevic, G.B. Christian, M.R. Davis, A. Gerbershagen, C. Perry
JAI, Oxford, United Kingdom
R. Apsimon, B. Constance
CERN, Geneva, Switzerland
J. Resta-López
IFIC, Valencia, Spain

A low-latency, sub-micron resolution stripline beam position monitoring system has been developed for use in single-pass beamlines. The fast analogue front-end signal processor is based on a single-stage RF down-mixer and is combined with an FPGA-based system for digitisation and further signal processing. The system has been deployed and tested with beam at the Accelerator Test Facility at KEK. Performance results are presented on the calibration, resolution and stability of the system. A detailed simulation has been developed that is able to account for the measured performance.

MOPPR066

Study of Transverse Pulse-to-Pulse Orbit Jitter at the KEK Accelerator Test Facility 2 (ATF2)

simulation, extraction, controls, linear-collider

936

J. Resta-López, J. Alabau-Gonzalvo
IFIC, Valencia, Spain
R. Apsimon, B. Constance, A. Gerbershagen
CERN, Geneva, Switzerland
D.R. Bett, P. Burrows, G.B. Christian, M.R. Davis, C. Perry
JAI, Oxford, United Kingdom

Funding: FPA2010-21456-C02-01
For future linear colliders the precise control and mitigation of pulse-to-pulse orbit jitter will be very important to achieve the required luminosity. Diagnostic techniques for the orbit jitter measurement and correction for multi-bunch operation are being addressed at the KEK Accelerator Test Facility 2 (ATF2). In this paper we present recent studies on the vertical jitter propagation through the ATF2 extraction line and final focus system. For these studies the vertical pulse-to-pulse position and angle jitter have been measured using the available stripline beam position monitors in the beamline. The cases with and without intra-train orbit feedback correction in the ATF2 extraction line are compared.

MOPPR080

Wire Scanner Beam Profile Measurements: LANSCE Facility Beam Development

electron, controls, target, linac

975

J.D. Gilpatrick, Y.K. Batygin, F. Gonzales, M.E. Gruchalla, V.G. Kutac, D. Martinez, C. Pillai, S. Rodriguez Esparza, J.D. Sedillo, B.G. Smith
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the U.S. Department of Energy.
The Los Alamos Neutron Science Center (LANSCE) is replacing Wire Scanner (WS) beam profile measurement systems. Three beam development tests have taken place to test the new wire scanners under beam conditions. These beam development tests have integrated the WS actuator, cable plant, electronics processors and associated software and have used H⁻ beams of different beam energy and current conditions. In addition, the WS measurement-system beam tests verified actuator control systems for minimum profile bin repeatability and speed, checked for actuator backlash and positional stability, tested the replacement of simple broadband potentiometers with narrow band resolvers, and tested resolver use with National Instruments Compact Reconfigurable Input and Output (cRIO) Virtual Instrumentation. These beam tests also have verified how trans-impedance amplifiers react with various types of beam line background noise and how the cable plants can be simplified without generating unwanted noise currents. This paper will describe these beam development tests and show some resulting data.

TUXA02

Upgrade Plans for the LHC Injector Complex

linac, injection, electron, vacuum

1010

R. Garoby, H. Damerau, S.S. Gilardoni, B. Goddard, K. Hanke, A.M. Lombardi, M. Meddahi, B. Mikulec, E.N. Shaposhnikova, M. Vretenar
CERN, Geneva, Switzerland

Challenging beams with much higher brightness than today are required for the LHC to achieve its high luminosity objective after the year 2020. It is the purpose of the LHC Injectors Upgrade (LIU) Project to achieve this result, consolidating and upgrading the existing set of ageing synchrotrons (PSB, PS and SPS), and using the new linac presently in construction (Linac4). The anticipated beam characteristics are described and compared to the known limitations in the different accelerators. The foreseen solutions are outlined as well as the planning for their implementation.

Slides TUXA02 [72.367 MB]

TUYA03

Performance and Prospects of BEPCII

luminosity, coupling, optics, injection

1030

Q. Qin
IHEP, Beijing, People's Republic of China

BEPCII, the upgrade project of Beijing Electron Positron Collider (BEPC), has been put into operation for both high energy physics experiments as well as synchrotron radiation application since its completion in 2009. The peak luminosity reaches 6.5*10³² cm^-2 s^-1 at 1.89 GeV with e⁺e⁻ collisions of each beam current 700 mA. The collider operates for dedicated synchrotron radiation mode with 250 mA electron beams at 2.5 GeV. The performance of BEPCII should be reported and the measures to upgrade its luminosity described.

Slides TUYA03 [5.529 MB]

TUOAB01

Timing and Synchronization for the APS Short Pulse X-ray Project

laser, cavity, LLRF, storage-ring

1077

F. Lenkszus, N.D. Arnold, T.G. Berenc, G. Decker, E.M. Dufresne, R.I. Farnsworth, Y.L. Li, R.M. Lill, H. Ma
ANL, Argonne, USA
J.M. Byrd, L.R. Doolittle, G. Huang, R.B. Wilcox
LBNL, Berkeley, California, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Short-Pulse X-ray (SPX) project, which is part of the APS upgrade, will provide intense, tunable, high-repetition-rate picosecond x-ray pulses through the use of deflecting cavities operating at the 8th harmonic of the storage-ring rf. Achieving this picosecond capability while minimizing the impact to other beamlines outside the SPX zone imposes demanding timing and synchronization requirements. For example, the mismatch between the upstream and downstream deflecting cavities' rf field phase is specified to be less than 0.077 degrees root mean squared (rms) at 2815 MHz (~77 femtoseconds). Another stringent requirement is to synchronize beamline pump-probe lasers to the SPX x-ray pulse to 400 femtoseconds rms. To achieve these requirements we have entered into a collaboration with the Beam Technology group at LBNL. They have developed and demonstrated a system for distributing stable rf signals over optical fiber capable of achieving less than 20 femtoseconds rms drift and jitter over 2.2 km over 60 hours*. This paper defines the overall timing/synchronization requirements for the SPX and describes the plan to achieve them.
* R. Wilcox et al. Opt. Let. 34(20), Oct 15, 2009

Slides TUOAB01 [2.515 MB]

TUEPPB006

Direct Numerical Modeling of E-Cloud Driven Instability of Three Consecutive Batches in the CERN SPS

electron, simulation, emittance, betatron

1125

J.-L. Vay, M.A. Furman, M. Venturini
LBNL, Berkeley, California, USA

Funding: Supported by the US-DOE under Contract DE-AC02-05CH11231, the SciDAC program ComPASS and the US-LHC Accelerator Research Program (LARP).
Electron clouds impose limitations on current accelerators that may be more severe for future machines, unless adequate measures of mitigation are taken. The simulation package WARP-POSINST was recently upgraded for handling multiple bunches and modeling concurrently the electron cloud buildup and its effect on the beam, allowing for direct self-consistent simulation of bunch trains generating, and interacting with, electron clouds. We have used the WARP-POSINST package on massively parallel supercomputers to study the buildup and interaction of electron clouds with a proton bunch train in the CERN SPS accelerator. Results suggest that a positive feedback mechanism exists between the electron buildup and the e-cloud driven transverse instability, leading to a net increase in predicted electron density.
Used resources of NERSC.

TUPPC061

Commissioning of a beta∗ Knob for Dynamic IR Correction at RHIC

optics, luminosity, quadrupole, insertion

1314

G. Robert-Demolaize, A. Marusic, S. Tepikian, S.M. White
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 addition to the recent optics correction technique demonstrated at CERN and applied at RHIC, it is important to have a separate tool to control the value of the beta functions at the collision point (beta∗). This becomes even more relevant when trying to reach high level of integrated luminosity while dealing with emittance blow-up over the length of a store, or taking advantage of compensation processes like stochastic cooling. Algorithms have been developed to allow modifying independently the beta function in each plane for each beam without significant increase in beam losses. The following reviews the principle of such algorithms and their experimental implementation as a dynamic beta-squeeze procedure.

TUPPC091

Simulation of Colliding Beams with Feedback in LHC

simulation, emittance, luminosity, kicker

1374

S. Paret, J. Qiang
LBNL, Berkeley, California, USA

Funding: This work supported partially by the US LHC Accelerator Research Program (LARP) of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Beam-beam effects impose restrictions on beam and beam optical parameters as they may degrade the luminosity and the emittance or cause coherent instabilities and particle loss. In the planned High Luminosity Large Hadron Collider (HL-LHC), beam-beam effects will significantly affect the beams because of unprecedented beam parameters and new features like crab cavities or elliptical beam cross sections at the interaction points. Noise from various sources can further worsen the situation. Therefore investigations are required to identify limitations of possible HL-LHC layouts. The impact of beam-beam effects on the beam dynamics is investigated by virtue of particle tracking simulations. Using the code BeamBeam3D and the strong-strong collision model, simulations including perturbations by noise and LHC's feedback system, an important means to mitigate transverse emittance growth due to coherent beam excitation, were carried out. The impact of numerical noise on the emittance in simulations and the state of the feedback modeling are presented.

TUPPP023

Operation Status of ALBA Synchrotron Light Source

storage-ring, vacuum, emittance, kicker

1659

M. Pont
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain

ALBA is a 3.0 GeV third generation synchrotron light source which has been commissioned during 2011. From October 2011 up to 7 beamlines are delivering beam for beamline commissioning, 6 from insertion devices and 1 from a bending magnet. Since April 2012 the facility is open to external users. Beam current has been continuously increased and the present stored beam current for users is 200 mA in a multi-bunch filling pattern. Orbit stability is kept at ±1 micron with a slow orbit feedback. The paper will review the operation and performance status of the different subsystems and review also the main objectives for 2012: target current of 400 mA, delivery of 3000 hours of beam to beamlines, testing of a fast orbit feedback system as well as preparations for top-up operation.

TUPPP034

BPM Gains and Beta Function Measurement Using MIA and FPGA BPMs at the APS

betatron, lattice, optics, quadrupole

1686

C.-X. Wang, G. Decker, H. Shang, C. Yao
ANL, Argonne, USA
D. Ji
IHEP, Beijing, People's Republic of China

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The broadband BPM system at the Advanced Photon Source (APS) is being upgraded with FPGA-based beam history modules, which fix problems in the old history modules and increase functionality. Using these new turn-by-turn BPMs and the newly developed real-time feedback system, measurement of BPM gains, beta function and other optics functions are being developed based on model-independent analysis of turn-by-turn data and model fitting, aiming at quasi-real-time and high-accuracy optics measurement. We will discuss our effort, especially experience with strong nonlinearity and wakefields typical of 3rd-generation light sources.

TUPPR028

Recent Improvements in the Orbit Feedback and Ground Motion Mitigation Techniques for CLIC

luminosity, quadrupole, simulation, ground-motion

1876

J. Snuverink, J. Pfingstner, D. Schulte
CERN, Geneva, Switzerland

The Compact Linear Collider (CLIC) accelerator has strong stability requirements on the position of the beam. In particular, the beam position will be sensitive to ground motion. A number of mitigation techniques have been proposed - quadrupole stabilization and positioning, final doublet stabilization as well as beam based orbit and interaction point (IP) feedback. Integrated studies of the impact of ground motion on the CLIC Main Linac (ML) and Beam Delivery System (BDS) that model the latest hardware designs have been performed. Furthermore, additional imperfections have been introduced and the robustness of this system is discussed in detail. The possibility of using ground motion measurements as an alternative to the quadrupole stabilization is investigated.

TUPPR032

Beam Stability at CTF3

klystron, pick-up, cavity, linac

1888

T. Persson, P.K. Skowroński
CERN, Geneva, Switzerland

The two beam acceleration tested in CTF3 imposes very tight tolerances on the drive beam stability. A description of the specialized monitoring tool developed to identify the drifts and jitter in the machine is presented. It compares all the relevant signals in an on-line manner for helping the operator to identify drifts or to log data for off-line analysis. The main sources for the drifts of the drive beam were identified and their causes are described. Feedbacks applied to the RF were implemented to reduce the effects. It works by changing the waveform for the pulse compression to compensate for the drifts.

TUPPR034

Beam-based Alignment in CTF3 Test Beam Line

quadrupole, alignment, beam-losses, injection

1894

G. Sterbini, S. Döbert, R.L. Lillestøl, E. Marín, D. Schulte
CERN, Geneva, Switzerland
E. Adli
University of Oslo, Oslo, Norway

The CLIC linear collider is based on the two beams acceleration scheme. During acceleration, the drive beam suffers a large increase in its energy spread. In order to efficiently transport such a beam, beam-based alignment techniques together with tight pre-alignment tolerances are crucial. A beam-based steering campaign has been conducted at the Test Beam Line of the CLIC Test Facility to evaluate the performance of several algorithms. In the following we present and discuss the obtained results.

TUPPR083

Kink Instability Suppression with Stochastic Cooling Pickup and Kicker

ion, electron, pick-up, kicker

2017

Y. Hao, M. Blaskiewicz, V. Litvinenko, V. Ptitsyn
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.
The kink instability is one of the major beam dynamics issues of the linac-ring based electron ion collider. This head-tail type instability arises from the oscillation of the electron beam inside the opposing ion beam. It must be suppressed to achieve the desired luminosity. There are various ways to suppress the instability, such as tuning the chromaticity in the ion ring or by a dedicated feedback system of the electron beam position at IP, etc. However, each method has its own limitation. In this paper, we will discuss an alternative opportunity of suppressing the kink instability of the proposed eRHIC at BNL using the existing pickup-kicker system of the stochastic cooling system in RHIC.

WEEPPB011

Analysis of High Field Non-Linear Losses on SRF Surfaces Due to Specific Topographic Roughness

simulation, superconductivity, niobium, SRF

2188

C. Xu
The College of William and Mary, Williamsburg, USA
M.J. Kelley, C.E. Reece, C. Xu
JLAB, Newport News, Virginia, USA

Funding: This work is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The high-field performance of SRF cavities will eventually be limited by the realization of fundamental material limits, whether it be Hc1 or Hsh, or some derivative thereof, at which the superconductivity is lost. Before reaching this fundamental field limit at the macro level, it must be encountered at localized, perhaps microscopic, sites of field enhancement due to local topography. If such sites are small enough, they may produce thermally stabilized normal-conducting regions which contribute non-linear losses when viewed from the macro resonant field perspective, and thus produce degradation in Q0. We have undertaken a calculation of local surface magnetic field enhancement from specific fine topographic structure by conformal mapping method and numerically. A solution of the resulting normal conducting volume has been derived and the corresponding RF ohmic loss simulated.

WEPPC006

CW and LP Operation Test of XFEL-Like Cryomodule

HOM, cryomodule, cavity, cryogenics

2215

J.K. Sekutowicz, V. Ayvazyan, M. Ebert, J. Eschke, A. Gössel, D. Kostin, I.M. Kudla, W. Merz, F. Mittag, R. Onken
DESY, Hamburg, Germany
W. Cichalewski, W. Jałmużna, K.P. Przygoda
TUL-DMCS, Łódź, Poland
K. Czuba, L. Zembala
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
J. Szewiński
The Andrzej Soltan Institute for Nuclear Studies, Centre Świerk, Świerk/Otwock, Poland

A continuous improvement in the performance of superconducting TESLA cavities will make possible, from the cryogenic point of view, operation of the XFEL linac in continuous wave (cw) mode at gradients up to 7.5 MV/m and in long pulse (lp) mode up to nominal gradient of 23.4 MV/m. Each of these new operation modes will offer an additional flexibility in time structure of the photon beam, and therefore will allow for more experiments and in some cases less demanding and less expensive equipment. In this contribution we discuss results of the first RF test of these new types of operation with a XFEL-like cryomodule.

WEPPC017

Design of a High-Speed Pulsed 324MHz Solid-State Amplifier for Use in a Beam Chopper

resonance, impedance, proton, insertion

2242

S.C. Dillon, B.S. Nobel, C.P. Schach
Tomco Technologies, Stepney, South Australia, Australia

A 324MHz 30kW high-speed pulsed solid-state amplifier has been designed for use in a beam chopper at the Japan Proton Accelerator Complex (J-PARC). This paper discusses the various design challenges and presents the initial performance test results. In particular, the amplifier achieves pulse rise and fall times of less than 15 nanoseconds, is easily upgradeable in power, and withstands 100% power reflection without damage.

WEPPC081

Measurement of the Mechanical Properties of Superconducting Cavities During Operation

cavity, resonance, linac, simulation

2399

S. Posen, M. Liepe
CLASSE, Ithaca, New York, USA

The Horizontal Test Cryostat (HTC) contains the first prototype 7-cell 1.3 GHz superconducting cavity for the Cornell ERL main linac. In this paper, experimental measurements of the cavity's mechanical properties are presented. The mechanical resonances were studied using a Dynamic Signal Analyzer, which measured the transfer function from the fast piezo tuner to itself and the cavity frequency. The microphonics detuning of the cavity was measured, and found to satisfy the specification that the maximum detuning be below 20 Hz, even without feedback from the piezos. Correlations were studied between the microphonics detuning and the helium pressure, piezo sense signal, and the ground vibrations. The Lorentz force detuning (LFD) coefficient was also measured. The frequencies of the mechanical resonances were compared to simulation. In addition, the performance of the frequency tuners was evaluated. Both the mechanical tuner and the piezo were found to be highly linear with very little hysteresis even on small scales.

WEPPD041

The Strategy between High Precision Temperature Control and Energy Saving for Air-Conditioning System

controls, monitoring, photon, target

2603

Z.-D. Tsai, W.S. Chan, J.-C. Chang, C.S. Chen, Y.-C. Chung, C.W. Hsu, C.Y. Liu
NSRRC, Hsinchu, Taiwan

In the Taiwan Light Source (TLS), several studies related to the temperature stability for air conditioning system continued to be in progress. Using new control philosophy can minimize temperature variations effectively. A high precision temperature control within ±0.05°C for air condition system has been conducted to meet the more critical stability requirement. Due to the importance of energy saving issue, the power consumption of air conditioning system was also upgraded and intended to reduce extensively. The paper addresses some experience between high precision temperature control and energy saving about operation of air conditioning system. The significant improvements proven that both targets can achieve simultaneously.

WEPPD048

Laser Synchronization at REGAE using Phase Detection at an Intermediate Frequency

laser, electron, controls, LLRF

2624

M. Felber, M. Hoffmann, U. Mavrič, H. Schlarb, S. Schulz
DESY, Hamburg, Germany
W. Jałmużna
TUL-DMCS, Łódź, Poland

A new linear accelerator is being set up for electron diffraction experiments at DESY. This machine, called REGAE (Relativistic Electron Gun for Atomic Exploration) is composed of a photo-cathode gun and a buncher cavity. It uses a single laser system for both, the generation of the electron bunches and for pump-probe experiments. The required timing jitter between the electron bunches and the laser pulses at the experiment is in the order of 10 fs rms. The conventional method for laser synchronization using RF technique to measure phase-jitter in the baseband is susceptible to distortions caused by ground-loops and electro-magnetic interference. At REGAE a new scheme for an RF-based laser synchronization is deployed. It uses a down-converter which mixes a higher harmonic of the laser repetition rate down to an intermediate frequency (IF). The IF is digitized and its phase calculated. This information is used for the feedback controller keeping the laser and the RF synchronized.

WEPPD074

Issues and Feasibility Demonstration of Positioning Closed Loop Control for the CLIC Supporting System Using a Test Mock-up with Five Degrees of Freedom

alignment, controls, collider, linear-collider

2696

M. Sosin, M. Anastasopoulos, N. Chritin, J. Kemppinen, H. Mainaud Durand, V. Rude, G. Sterbini, S. griffet
CERN, Geneva, Switzerland

Since several years, CERN is studying the feasibility of building a high energy e⁺ e⁻ linear collider: the CLIC (Compact LInear Collider). One of the challenges of such a collider is the pre-alignment precision and accuracy requirement on the transverse positions of the linac components, which is typically 14 μm over a window of 200 m. To ensure the possibility of positioning within such tight constraints, CERN Beams Department’s Survey team has worked intensively at developing the methods and technology needed to achieve that objective. This paper describes activities which were performed on a test bench (mock-up) with five degrees of freedom (DOF) for the qualification of control algorithms for the CLIC supporting system active-pre-alignment. Present understanding, lessons learned (“know how”), issues of sensors noise and mechanical components nonlinearities are presented.

WEPPP059

First Measurements with Multibunch Feedback Systems at the Fast Ramping Stretcher Ring ELSA

kicker, damping, cavity, electron

2840

M. Schedler, F. Frommberger, N. Heurich, W. Hillert, A. Roth, R. Zimmermann
ELSA, Bonn, Germany

Funding: Supported by German Research Foundation through SFB/TR 16.
At the Electron Stretcher Facility ELSA of Bonn University, an upgrade of the maximum stored beam current from 20 mA to 200 mA is planned. The storage ring operates applying a fast energy ramp of 4 GeV/s from 1.2 GeV to 3.5 GeV. The intended upgrade is mainly limited due to the excitation of multibunch instabilities. As a countermeasure, we succesfully commissioned state-of-the-art bunch by bunch feedback systems in the longitudinal and the two transverse dimensions. First results concerning the commissioning of the systems as well as the operation during the fast energy ramp will be presented. In particular, the performance while controlling the motion of every single bunch, especially in controlled bunch cleaning, will be discussed.

WEPPP060

A Robust Transverse Feedback System

kicker, status, optics, pick-up

2843

M. Alhumaidi, A.M. Zoubir
TU Darmstadt, Darmstadt, Germany

Transverse feedback systems use pickups signals to measure the beam instabilities and kickers to correct the beam. The correction signal is calculated according to the transfer matrices between the pickups and the kickers. However, errors due to magnetic field imperfections and magnets misalignments lead to deviations in the transfer matrices from their nominal values, which affects the feedback quality in a negative manner. In this work we address a new concept for robust feedback system against optics errors or uncertainties. A kicker and multiple pickups are used for each transversal direction. We introduce perturbation terms to the transfer matrices between the kicker and the pickups. Consequently, the Extended Kalman Filter is used to estimate the feedback signal and the perturbation terms by means of the measurements from the pickups. Finally results for the heavy ions synchrotron SIS 18 at the GSI are shown.

WEPPP062

Characterization and Stabilization of Multi-Bunch Instabilities at the ANKA Storage Ring

kicker, storage-ring, injection, controls

2849

E. Huttel
FZK, Karlsruhe, Germany
N. Hiller, E. Huttel, V. Judin, B. Kehrer, S. Marsching, A.-S. Müller, N.J. Smale
KIT, Karlsruhe, Germany

ANKA is a 2.5 GeV storage ring for synchrotron radiation. Up to 200 mA are accumulated at 0.5 GeV and then ramped to 2.5 GeV. In the past storage ring operation suffered from vertical multi-bunch instabilities. These could partially be cured by increased chromaticity, a large gap in the filling structure and by keeping the beam longitudinally unstable. A vertical digital bunch-by-bunch system from ITECH has been installed that allows an operation of the storage ring without exciting the longitudinal modes. In addition, the system allows analyzing multi-bunch instabilities both transverse and longitudinal and their dependence from cavity temperature, filling structure and chromaticity. This paper reports on our experience operating this system and presents an investigation of multi-bunch modes in the ANKA storage ring.

WEPPP065

Status of the SSRF Fast Orbit Feedback System

controls, storage-ring, electron, insertion

2855

B.C. Jiang, J. Hou, C.X. Yin, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

The fast orbit feedback system with bandwidth up to 100Hz is under commissioning at SSRF. The main purposes of the system are to suppress the short term orbit stability under sub-micron level and to compensate the orbit distortions caused by changing gaps of the insertion devices. The layout of the system is described and the preliminary commissioning results are given out in this paper.

WEPPP066

Performance Simulations of a Phase Stabilization System Prototype for CTF3

kicker, simulation, collider, linac

2858

A. Gerbershagen, T. Persson, D. Schulte, P.K. Skowroński
CERN, Geneva, Switzerland
P. Burrows, G.B. Christian
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
A. Gerbershagen, C. Perry
JAI, Oxford, United Kingdom
E. Ikarios
National Technical University of Athens, Athens, Greece

The CLIC drive beam provides RF power for acceleration of the main beam, and hence the drive beam’s longitudinal phase tolerances are very tight. A feedforward chicane consisting of four electromagnetic kickers is proposed as a correction system for the phase errors, which should allow loosening of the tolerances. A prototype of such a chicane system, developed by CERN, INFN and the University of Oxford, is planned to be installed at CFT3 in 2012. The present paper summarizes the parameters of the planned phase correction system and presents simulations, which are used to make predictions of the performance of such a feedforward system at CTF3.

WEPPP067

Commissioning Results of Slow Orbit Feedback using PID Controller Method for the Siam Photon Source

controls, photon, storage-ring, LabView

2861

S. Klinkhieo, S. Boonsuya, P. Klysubun, S. Krainara, P. Songsiriritthigul, P. Sudmuang, N. Suradet
SLRI, Nakhon Ratchasima, Thailand
S. Rujirawat
Suranaree University of Technology, Nakhon Ratchasima, Thailand

A slow orbit feedback (SOFB) system has been developed to improve the orbit stability for the storage ring of the Siam Photon Source (SPS). The SOFB uses a PID controller method utilizing LabVIEW channel to access 20 BPMs and 28 correctors of the storage ring. The first phase implementation of the feedback loops based on this method was operated at 0.05Hz of sampling frequency, which reduce the fluctuation of both horizontal and vertical positions of the orbit from ~200 microns down to ~30 microns. The commissioning results indicate that further work and hardware upgrade are required. A higher sampling frequency at least 30Hz is strongly required for PID controller implementation. Upgrading of the existing 12-bit resolution corrector power supplies is also necessary. The basic principle of PID algorithms, hardware, software and commissioning results of the current SOBF system, as well as a future development plan, will be presented.

WEPPP068

Latest Performance Results from the FONT5 Intra-train Beam Position and Angle Feedback System at ATF2

kicker, extraction, linear-collider, collider

2864

D.R. Bett, R. Apsimon, N. Blaskovic Kraljevic, P. Burrows, G.B. Christian, M.R. Davis, A. Gerbershagen, C. Perry
JAI, Oxford, United Kingdom
B. Constance
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 time scales, 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. The latest results from beam tests at ATF2 will be presented, including the system latency and correction performance.

WEPPP069

Performance Enhancements for the Transverse Feedback System at the Advanced Photon Source

EPICS, storage-ring, photon, controls

2867

N.P. Di Monte, R.I. Farnsworth, A.J. Scaminaci
ANL, Argonne, USA

With the success of the transverse feedback system at the Advanced Photon Source (APS), an upgrade to this system is being developed. The current system is operating at a third of the storage ring bunch capacity, or 324 of the available 1296 bunches. This upgrade will allow the sampling of all 1296 bunches and make corrections for all selected bunches in a single storage ring turn. To facilitate this upgrade, a new analog I/O board capable of 352-MHz operation is being developed along with a P0 bunch cleaning circuit. The clock cleaning circuit is also needed for the high speed analog output circuit, which is transmitted about 200 m to a separate DAC unit in real time. This remote DAC will have its transceiver data rate triple from 2.3 Gb to about 7 Gb on a fiber optic link. This paper will discuss some of the challenges in reducing the clock jitter from the system P0 bunch clock along with the necessary FPGA hardware upgrades and algorithm changes, all of which are required for the success of this upgrade.

WEPPP070

Simulation of the APS Storage Ring Orbit Real-Time Feedback System Upgrade Using MATLAB

storage-ring, simulation, controls, dipole

2870

S. Xu, G. Decker, R.I. Farnsworth, F. Lenkszus, H. Shang, X. Sun
ANL, Argonne, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) storage ring orbit real-time feedback (RTFB) system plays an important role in stabilizing the orbit of the stored beam. An upgrade is planned that will improve beam stability by increasing the correction bandwidth to 200 Hz or higher. To achieve this, the number of available steering correctors and beam position monitors (BPMs) will be increased, and the sample rate will be increased by an order of magnitude. An additional benefit will be the replacement of aging components. Simulations have been performed to quantify the effects of different system configurations on performance.

WEPPP071

Phase Noise Studies at the Advanced Photon Source

simulation, storage-ring, synchrotron, photon

2873

N. Sereno, G. Decker, R.M. Lill, B.X. Yang
ANL, Argonne, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Phase noise generated primarily by power line harmonics modulating the 352-MHz rf system in the APS storage ring is a dominant source of high- frequency beam motion, both longitudinally and transversely, due to dispersion in the lattice. It also places fundamental limits on the ability to generate picosecond-scale x-ray pulses for fast pump / probe experiments*. Measurements using turn-by-turn beam position monitors (BPMs) located at high-dispersion locations are compared and contrasted with results from a dedicated S-band phase detector connected to either a capacitive pickup electrode or a diamond x-ray detector. Horizontal beam position at high-dispersion locations is related directly to beam phase by a very simple relation involving the momentum compaction. Simulation results are used to validate this relationship and to quantify the relation between phase noise on the main rf vs beam arrival time jitter.
* A. Zholents et al., NIM A 425, 385 (1999).

WEPPP073

Dynamic Feedback Model for High Repetition Rate Linac-driven FELs

linac, FEL, cavity, beam-loading

2879

J.M. Byrd, L.R. Doolittle, P. Emma, G. Huang, A. Ratti, C. Serrano
LBNL, Berkeley, California, USA

Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
One of the concepts for the next generation of linac-driven FELs is a cw superconducting linac driving an electron beam with MHz repetition rates. One of the challenges for next generation FELs is improve the shot-to-shot stability of the energy, charge, peak current, and timing jitter of the electron beam. The use of a cw RF system with MHz beam repetition rates presents an opportunity to use broadband feedback to stabilize the beam parameters. To understand the performance of such a feedback system, we are are developing a dynamic feedback model of the machine with a focus on the longitudinal beam properties. The model is being developed as an extension of the LITrack code and will include the dynamics of the beam-cavity interaction, RF feedback, beam-based feedback, and multibunch effects. In this paper, we will present the status of this model along with results.

WEPPP074

Study of a Wideband Feedback Kicker for the SPS

kicker, impedance, cavity, simulation

2882

S. De Santis, Z. Paret, A. Ratti
LBNL, Berkeley, California, USA
A. Gallo, F. Marcellini
INFN/LNF, Frascati (Roma), Italy

Funding: Work supported by the US Department of Energy under Contracts DE-AC02-05CH11231 and DE-AC02-76SF00515, and through the US LHC Accelerator Research Program (LARP).
The LHC luminosity upgrade currently being planned at CERN depends in large measure on a successful upgrade of its injectors chain. In particular the storing of higher currents in the SPS presents a significant challenge from the point of view of the beam stability. Electron cloud driven and transverse mode-coupled instabilities can disrupt the stored beam to the point of making injection in the LHC impossible. These types of instabilities are characterized by fast growth times and substantial spectral components at high frequency. Therefore a key aspect of any feedback system capable of effectively controlling the instability growth is the development of a suitable kicker with a high frequency response. In this paper we investigate the technologies available for such a kicker and identify a possible solution to be implemented on the SPS. By combining a lower frequency stripline kicker with a high frequency module, such as a damped cavity or a slotted waveguide, it would be possible to provide shunt impedances around 1000 Ω on a bandwidth from DC to 1 GHz. The basic parameters and limits of such a solution are discussed.

WEPPP076

Analysis of Numerical Noise in Particle-In-Cell Simulations of Single-Bunch Transverse Instabilities and Feedback in the CERN SPS

simulation, emittance, pick-up, kicker

2888

R. Secondo, J.-L. Vay, M. Venturini
LBNL, Berkeley, California, USA

Funding: Work supported by the US-DOE and the US-LHC Accelerator Research Program LARP under Contract DE-AC02-05CH11231. Used resources of NERSC and the Lawrencium cluster at LBNL
The operation at high current of the SPS at CERN is limited by transverse Single-Bunch instabilities generated by the effect of electron clouds. A model of a high bandwidth feedback control system has been implemented in the macro-particle code WARP to study bunch dynamics and identify system requirements for the efficient damping of single-bunch transverse instability. We analyze the effect of numerical noise and choice of simulation parameters on the modeling of beam dynamics, focusing in particular on the investigation of the feedback system requirements of minimum power to damp the instability and frequency bandwidth given a fixed gain. We report on simulation results and discuss the plans for the future improvements of the feedback model.

WEPPP077

Control of RF Transients in Cavities Induced by Pulsed High Current Beams

cavity, SRF, controls, linac

2891

F. Löhl, J. Dobbins, R.P.K. Kaplan, C.R. Strohman
CLASSE, Ithaca, New York, USA

Funding: Supported by NSF award DMR-0807731.
The Cornell ERL prototype injector is operated either in a cw or in a pulsed mode. In the latter case, the bunch trains, which have a duration of 100 ns to 10 microseconds and a beam current of up to 100 mA, generate transients in the RF cavity fields which severely distort the beam quality and cause beam loss. In this paper, we present a scheme we use to correct the fast transients based on an adaptive feed-forward method.

WEPPP078

Status of the Mixed-signal Active Feedback Damper System for Controlling Electron-proton Instabilities for the Spallation Neutron Source

pick-up, damping, kicker, proton

2894

Z.P. Xie, M.J. Schulte
UW-Madison, Madison, Wisconsin, USA
C. Deibele
ORNL, Oak Ridge, Tennessee, USA

Funding: Work supported by Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy
As the beam intensity at the Spallation Neutron Source (SNS) in Oak Ridge National Laboratory (ORNL) is leveled up, it becomes necessary to have greater control over the electron-proton (e-p) instability. This paper presents an updated design of a mixed-signal transverse feedback system for active damping of the e-p instability. It describes the design, features and results of this feedback damper and reviews several experimental studies to understand the system performance and its limitations. The updated mixed-signal feedback damper system employs power amplifiers (PAs), analog-to-digital converters (ADCs), multiple field programmable gate array (FPGA) chips, and digital-to-analog converters (DACs) to provide feedback damping and system monitoring. Unlike existing analog damping systems, FPGA-based feedback damping systems offer programmability while maintaining high performance. The system gain, delay and digital signal processing components can be programmed during the fly to perform timing adjustments, correct for ring harmonics, and equalize magnitude and phase dispersions.

WEPPP083

Near Real-time Response Matrix Calibration for 10-Hz GOFB

dipole, damping, injection, quadrupole

2903

C. Liu, R.L. Hulsart, A. Marusic, K. Mernick, 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.
The 10-Hz global orbit feedback, for damping the trajectory perturbation (~10 Hz) due to the vibrations of the triplets, is operational for injection and store in RHIC. The operation of the system has been performed using transfer functions between the beam position monitors and correctors obtained from the online optics model and a correction algorithm based on singular value decomposition (SVD). Calibration of the transfer functions by measuring the beam position oscillations while modulating the dedicated correctors has been carried out. The feedback results with model matrix and measured matrix will be compared.

WEPPP084

Weighted SVD Algorithm for Close-Orbit Correction and 10 Hz Feedback in RHIC

electron, proton, closed-orbit, ion

2906

C. Liu, R.L. Hulsart, A. Marusic, R.J. Michnoff, M.G. Minty, V. Ptitsyn
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.
Measurements of the beam position along an accelerator are typically treated equally using standard SVD-based orbit correction algorithms so distributing the residual errors, modulo the local beta function, equally at the measurement locations. However, sometimes a more stable orbit at select locations is desirable. In this paper, we introduce an algorithm for weighting the beam position measurements to achieve a more stable local orbit. The results of its application to close-orbit correction and 10-Hz orbit feedback will be shown and analyzed.

WEPPP089

Study of the Combined Controller for Adjusting and Locking a Girder with Micrometer-level at NSRRC

controls, monitoring, storage-ring, synchrotron

2921

H.S. Wang, M.L. Chen, W.Y. Lai, S.Y. Perng, Y.L. Tsai, T.C. Tseng
NSRRC, Hsinchu, Taiwan
J.-R. Chen
NTHU, Hsinchu, Taiwan

A girder control system is proposed to quickly and precisely adjust the displacement and rotating angle of all girders in the storage ring with little manpower at the Taiwan Photon Source (TPS) project at National Synchrotron Research Center (NSRRC). In this control girder system, six motorized cam movers supporting a girder are driven on three pedestals to perform six-axis adjustments of a girder. To increase the nature frequency of a girder, the locking system is applied to promote the stiffness of a girder structure. The locking system consists of six locking mechanisms attached to three inboard pedestals and a locking controller. The study of the girder control system and the locking system control combined are achieving to the positioning with micrometre-level. This paper presents details of the study and tests of the combined controller.

WEPPP090

Stable RF Distribution System for the S-band Linac

controls, linac, klystron, extraction

2924

T. Naito, K. Ebihara, S. Nozawa, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
M. Amemiya
AIST, Tsukuba, Japan

The phase stabilization of the RF phase is key issue for the stable linac operation. An RF distribution system with femto-second stability has been developed for S-band linac using optic fiber links. The system uses a phase stabilized optical fiber (PSOF) and an active fiber length stabilization.* The phase stability is 0.1 degree (100f s) for 24 hours observation. In this paper, we present the test results of the system stability and evaluation of the existing RF reference line by using this system.
* Naito et. al. IPAC10 MOPC146

WEPPR049

The Impact of Fill Patterns on the Fast Ion Instability in the ILC Damping Ring

ion, damping, emittance, electron

3036

G.X. Xia
MPI-P, München, Germany

The ions produced via collisional ionization of the residual gas molecules in vacuum pipe with the circulating electron beam have deleterious effect on the beam properties and may become a limiting factor in the machine’s performance. In this paper, the various beam fill patterns are investigated and their effects on the fast ion instability are discussed. The simulations show that an optimal fill pattern can reduce growth rate of the fast ion instability significantly.

WEPPR058

The Vertical Impedance Distribution Measurement Using Response Matrix Method at BEPCII BPR

impedance, kicker, injection, betatron

3057

Y. Wei, D. Ji
IHEP, Beijing, People's Republic of China

Funding: Work supported by the Chinese National Foundation of Natural Sciences, contract 111100512108.
In the last run of BEPCII, the single bunch current is limited to about 8mA by the beam-beam effect. To obtain the design luminosity, larger number of bunches are necessary. But higher total current may be limited by the collective effects. A good understanding of the transverse impedance distribution around the BEPCII storage ring is required. Response matrix method has been applied successfully in BEPCII to fit the quadrupole errors and restore the optics. We can also calculate the variation of betatron phase advance around the ring with different single bunch current using the response matrix method and the transverse impedance distribution is thus deduced. In this paper, the first measurement of transverse impedance in BEPCII is presented.

WEPPR069

Measurements and Simulations of Transverse Coupled-Bunch Instability Rise Times in the LHC

simulation, injection, octupole, impedance

3087

N. Mounet, R. Alemany-Fernandez, W. Höfle, D. Jacquet, V. Kain, E. Métral, L. Ponce, S. Redaelli, G. Rumolo, R. Suykerbuyk, D. Valuch
CERN, Geneva, Switzerland

In the current configuration of the LHC, multibunch instabilities due to the beam-coupling impedance would be in principle a critical limitation if they were not damped by the transverse feedback. For the future operation of the machine, in particular at higher bunch intensities and/or higher number of bunches, one needs to make sure the coupled-bunch instability rise times are still manageable by the feedback system. Therefore, in May 2011 experiments were performed to measure those rise times and compare them with the results obtained from the LHC impedance model and the HEADTAIL wake fields simulation code. At injection energy, agreement turns out to be very good, while a larger discrepancy appears at top energy.

WEPPR084

Measurement of Coherent Damping Rate of the APS Storage Ring

damping, kicker, storage-ring, pick-up

3126

C. Yao, K.C. Harkay, H. Shang, C.-X. Wang
ANL, Argonne, USA

Funding: Work supported by U.S. Department of Energy, Offices of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The APS storage ring is a 7-GeV electron storage ring with a single-bunch current of up to 16 mA during normal user operations. To overcome beam instability we employ both chromatic correction and bunch-by- bunch feedback system. Typically we run a chromaticity of 4 for a 24-single fill pattern and 9 for a hybrids fill pattern in both planes with the feedback system loops closed. The APS upgrade (APS-U) calls for a beam current of 150 mA and installation of vertical deflecting cavities for short X-ray (SPX) production. In order to estimate whether the current chromatic correction and feedback system are adequate for the upgrade, we performed coherent damping rate measurements with two methods: kicking the beam with a kicker pulse and exciting the beam with the feedback system. We conclude that with a chromaticity of 4 in both planes, we can achieve a damping rate of 3 kHz in the x- plane and 2 kHz in the y-plane with feedback loops closed. Similar damping rates can also be achieved with chromatic correction alone. A special fitting program was developed to perform the damping rate analysis. This report presents the measurement data and results of the analysis.

WEPPR087

Dependence of Beam Instabilities Caused by Electron Clouds at CesrTA Due to Variations in Chromaticity, Bunch Current and Train Length

betatron, electron, emittance, positron

3135

M.G. Billing, G. Dugan, M.J. Forster, D.L. Kreinick, R.E. Meller, M.A. Palmer, G. Ramirez, M.C. Rendina, N.T. Rider, J.P. Sikora, K.G. Sonnad, H.A. Williams
CLASSE, Ithaca, New York, USA
J.Y. Chu
CMU, Pittsburgh, Pennsylvania, USA
J.W. Flanagan
KEK, Ibaraki, Japan
R. Holtzapple, M. Randazzo
CalPoly, San Luis Obispo, California, USA

Funding: Work supported by DOE Award DE-FC02-08ER41538, NSF Award PHY-0734867 and the Lepton Collider R&D Coop Agreement: NSF Award PHY-1002467.
Electron cloud-induced beam dynamics is being studied at CESRTA under various conditions. These measurements detect the the coherent self-excited spectrum for each bunch within a train and bunch-by-bunch beam size. In the position spectrum coherent betatron dipole and head-tail motion is detectable for each individual bunch within the train with a sensitivity for the motion of 1.1 (2) microns-rms in the vertical (horizontal) direction for a 1 mA bunch current. These techniques are utilized to study the electron cloud-related interactions, which cause the growth of coherent motion and beam size along the train. We report on the observations and results from studies of the instability growth vs. changes in chromaticity, the current per bunch and the length of the train.

WEPPR090

A 4.2 GS/s Synchronized Vertical Excitation System for SPS Studies - Steps Toward Wideband Feedback

controls, kicker, injection, acceleration

3144

J.D. Fox, J.J. Olsen, C.H. Rivetta, I.I. Rivetta, O. Turgut, S. Uemura
SLAC, Menlo Park, California, USA
W. Höfle, 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).
A 4.2 GS/s beam excitation system with accelerator synchronization and power stages is described. The system is capable of playing unique samples (32 samples/bunch) for 15,000 turns on selected bunch(es) in the SPS in synchronism with the injection and acceleration cycle. The purpose of the system is to excite internal modes of single-bunch vertical motion, and study the bunch dynamics in the presence of developing Electron cloud or TMCI effects. The system includes a synchronized master oscillator, SPS timing functions, an FPGA based arbitrary waveform generator, 4.2 GS/sec. D/A system and four 80W 20 -1000 MHz amplifiers driving a tapered stripline pickup/kicker. A software GUI allows specification of various modulation signals and selection of bunches and turns to excite, while a remote control interface allows simple control/monitoring of the RF power stages located in the tunnel. Excitation signals developed to excite head-tail and other modes of vertical motion are illustrated. The successful use of this system for SPS MD measurements in August and November 2011 is a vital proof-of-principle for wideband feedback using similar functions to correct the beam motion.

WEPPR091

Multi-Particle Simulation Codes Implementation to Include Models of a Novel Single-bunch Feedback System and Intra-beam Scattering

emittance, simulation, electron, damping

3147

M.T.F. Pivi, A. Chao, C.H. Rivetta
SLAC, Menlo Park, California, USA
F. Antoniou, K.S.B. Li, Y. Papaphilippou
CERN, Geneva, Switzerland
M. Boscolo, T. Demma
INFN/LNF, Frascati (Roma), Italy
K.G. Sonnad
CLASSE, Ithaca, New York, USA

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP).
The beam tracking codes C-MAD and HEAD-TAIL have been enhanced to include a detailed model of a single-bunch feedback system. Such a system is under development to mitigate the electron cloud and the transverse mode coupling instability (TMCI) in the SPS and LHC at CERN. This paper presents the model of the feedback sub-systems: receiver, processing channel, filter, amplifier and kicker, which takes into account the frequency response, noise, mismatching and technological limits. With a realistic model of the hardware, it is possible to study the prototypes installed in the SPS and design a novel feedback system. The C-MAD code, which is parallel and optimized for speed, now also includes radiation damping and quantum excitation and a detailed model of Intra-Beam Scattering (IBS) based on the Zenkevich-Bolshakov algorithm, to investigate the IBS during damping and its effect on the beam distribution, especially the beam tails, that analytical methods cannot investigate. Intra-beam scattering is a limiting factor for ultra-low emittance rings such as CLIC and Super-B.

THEPPB014

LLRF Testing of Superconducting Cryomodules for the European XFEL

cavity, cryomodule, LLRF, controls

3263

J. Branlard, V. Ayvazyan, T. Jeżyński, H. Schlarb
DESY, Hamburg, Germany
W. Cichalewski, W. Jałmużna, A. Piotrowski
TUL-DMCS, Łódź, Poland

During the installation phase of the European XFEL (2014), an average of one superconducting cryomodule per week will be tested and validated before being installed into the XFEL tunnel. Extensive tests will be carried in order to assess the RF performance of each cryomodule. A series of low level RF (LLRF) tests are planned as part of this validation phase, and will assess the cryomodule effective operating gradient, tuning range, compensation of Lorentz force detuning and microphonic behavior. These tests will be carried at DESY, in the Cryomodule Test Bench (CMTB) during the early stage of cryomodule production, and later at the Accelerating Module Test Facility (AMTF). Due to the pace and quantity of the modules to be tested, these tests have to be fully automated. This contribution presents the LLRF tests for the XFEL cryomodule validation, the challenges associated with automation, along with the first experimental results obtained on pre-series cryomodules tested at CMTB.

THPPC056

Development of 12kW RF Power Supply for CYCHU-10 Cyclotron

power-supply, cavity, cyclotron, impedance

3416

D. Li, T. Hu, J. Huang, K.F. Liu, B. Qin, J. Yang, L. Yang
Huazhong University of Science and Technology (HUST), Wuhan, People's Republic of China

One 12kW RF power supply has been developed for CYCHU-10, which is a 10 MeV cyclotron developed in Huazhong University of Science and Technology (HUST). A high performance DDS chip AD9859 is used to synthesize RF signal in this power supply, which is easy to change the output frequency. The centre frequency is 101MHz, and the frequency bandwidth is more than 1MHz. The RF power supply could operate in fine searching mode, coarse searching mode, tracking mode, and so on. It could search the resonant frequency of cavity with the frequency control loop. The final stage amplifier using a triode 3CW20,000H7 operates in grounded grid configuration, which is stable and reliable. The performance test using a 50Ω resistor load has finished, and major results are shown in this paper.

THPPC063

Commission of RF Power Sources and its Auxiliary Components for TPS in NSRRC

klystron, controls, cavity, synchrotron

3437

T.-C. Yu, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Y.-H. Lin, C.H. Lo, M.H. Tsai, Ch. Wang, T.-T. Yang, M.-S. Yeh
NSRRC, Hsinchu, Taiwan

Since 2010, before the starting the construction of TPS building in NSRRC, the intensive testing activities for RF facility has begun in RF lab. The RF facility includes 300kW transmitters, 350kW ferrite loads and 350kW circulators with the corresponding LLRF prototype system. Some unexpected situation happened, such as HV weak transformers and loosen greased ferrite tiles during the commission of the 300kW transmitter. Those situation are all encountered during long-term reliability test. For a high availability of beam light in TPS, the highly reliable sub-systems are the basic requirement and hence, long-term reliability is so essential during commission period. Then, the high power circulators for safe RF operation are also tested for various phases change at cavity port. The temperature compensation unit plays key role in proper operation of circulator. Some noticeable test procedure and results would also be introduced as the present RF system progress of TPS plan in NSRRC.

THPPC076

Comparison of LLRF Control Approaches for High Intensity Hadron Synchrotrons: Design and Performance

controls, cavity, beam-loading, synchrotron

3464

K. Gross, J. Adamy
TU Darmstadt, RTR, Darmstadt, Germany

Funding: Federal Ministry of Education and Research
A usual and effective way to realize closed-loop controllers is to use cascaded SISO feedback and to rely on some kind of linear PID structure with parameters adjusted manually in simulations or experiments. Such a control may not reach optimal performance if the system is coupled or non-linear. Regarding intense beams, longitudinal beam loading can be compensated by detuning. But the coupling between phase and amplitude (or I and Q component) highly depends on the tuning, that is on the resonant frequency of the cavity. It is derived that cavity and beam dynamics thus show bi-linear nature, i.e. belong to a well investigated class of non-linear systems with appropriate control strategies available*. Different controller designs are compared in terms of performance but also design transparency, the need of previous knowledge like the expected magnitude of beam loading and adaptability to different conditions, e.g. during acceleration or if applied to the full range of ion species as at GSI. The performance evaluation is based on macro-particle tracking simulations. In particular avail and limits of an optimal (quadratic cost) MIMO controller for bi-linear systems are shown**.
* H.K. Khalil: Nonlinear Systems, 3rd Edition, Prentice-Hall, 2002
** Z. Aganović, Z. Gajić: Linear Optimal Control of Bilinear Systems, Springer-Verlag, 1995.

THPPC079

Prototype Performance of Digital LLRF Control System for SuperKEKB

controls, cavity, LLRF, pick-up

3470

T. Kobayashi, K. Akai, K. Ebihara, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri
KEK, Ibaraki, Japan
H. Deguchi, K. Harumatsu, K. Hayashi, J. Nishio, M. Ryoshi
Mitsubishi Electric TOKKI Systems, Amagasaki, Hyogo, Japan

For the SuperKEKB project, a new LLRF control system has been developed to realize high accuracy and flexibility. It is an FPGA-based digital RF feedback control system using 16-bit ADC's, which works on the μTCA platform. In this μTCA-module, the Linux-OS runs then it performs as the EPICS-IOC. This LLRF system is available to both of normal-conducting cavity and super-conducting cavity. A prototype of the LLRF control system for the SuperKEKB was produced. The feedback control stability, temperature characteristics and cavity-tuner control performance are evaluated. The evaluation results and future issue for the operation will be presented in this report. The amplitude and phase stability in the feedback control is 0.03% and 0.02 degrees, respectively. It is sufficiently stable for the SuperKEKB. However, the temperature dependency is not small for the required stability. Its countermeasures are under consideration.

THPPC082

Control Performance Improvement by Using Feedforward in LLRF

controls, klystron, cavity, LLRF

3476

R. Zeng, D.P. McGinnis, S. Molloy
ESS, Lund, Sweden
A.J. Johansson
Lund University, Lund, Sweden

The LLRF design is ongoing at ESS (European Spallation Source). One major task of LLRF is to overcome a variety of perturbations such as klystron droop and ripple, Lorentz detuning and beam loading. These perturbations can be well suppressed by classical PI (proportional-integral) controller in feedback loop, but at a cost of raising risk of instability and consuming power overhead for overshoot. Since ESS is a green project focusing on energy efficiency, we will hence investigate in this paper some feedforward and advanced adaptive algorithms to deal with these perturbations, so as to improve the control performance and reduce the power overhead.

THPPC083

Investigation of Feedback Control for Klystron Ripple

cavity, klystron, controls, cathode

3479

R. Zeng, D.P. McGinnis, S. Molloy
ESS, Lund, Sweden
A.J. Johansson
Lund University, Lund, Sweden

At ESS (European Spallation Source), there might be potentially serious droop and ripple because of long RF pulse more than 3 ms. It is important for us to know to what extent the droop and ripple affects the klystron output, and how much we can tolerate. The variations of the phase and amplitude of klystron output due to the change in klystron cathode voltage is investigated in this Paper. The mechanism and the effectiveness of the feedback control to suppress the variations are given. To understand the limitation of the feedback, both proportional controller and proportional-integral controller used in feedback loop are simulated and analyzed respectively for superconducting cavity and normal conducting cavity. The tolerances of the droop and ripple in cathode voltage under feedback control are shown according to the data and results obtained.

THPPC084

LHC One-turn Delay Feedback Commissioning

cavity, klystron, LLRF, beam-loading

3482

T. Mastoridis, P. Baudrenghien, J.C. Molendijk
CERN, Geneva, Switzerland

The 1-turn delay feedback is an FPGA based feedback system part of the LHC cavity controller, which produces gain only around the revolution frequency harmonics. As such, it helps reduce the transient beam loading and effective cavity impedance. Consequently, it increases the stability margin for Longitudinal Coupled Bunch Instabilities driven by the cavity impedance at the fundamental and allows reliable operation at higher beam currents. The 1-turn delay feedback was commissioned on all sixteen cavities in mid-October 2011 and was used in operation for the rest of the run. The commissioning procedure and algorithms for setting-up are presented. The resulting improvements in transient beam loading, beam stability, and required klystron power are analyzed. The commissioning of the 1-turn delay feedback reduced the cavity voltage phase modulation from approximately six degrees peak-to-peak to below one degree at 400 MHz.

THPPC090

Robust Control of a Two-Input Two-Output (TITO) Multistate Cavity RF System ith Mismatched Uncertainty

cavity, controls, simulation, LLRF

3494

S. Kwon, M.S. Prokop, A. Scheinker
LANL, Los Alamos, New Mexico, USA

A RF cavity is well modeled as a linear two input two output (TITO) system in the Inphase/Quadrature (IQ) coordinates and is both controllable and observable. Whether it is due to the beam loading or Lorentz force detuning of a superconducting cavity, a cavity frequency detuning can be modeled as a matched uncertainty. The cavity field of a TITO cavity system with a matched uncertainty is controlled by output feedback or state feedback, whose error bound is made arbitrary small. Because of the building cost of the RF system, the single RF source (single klystron)-multicavity structure is sometimes used. This structure is described as a two-input multiple-output (TIMO) system. The control problem is not a simple extension of the single TITO system. Though the controllability and observability are preserved, the matched uncertainty of the TITO cavity system caused by cavity detuning becomes a mismatched uncertainty. The error bound of outputs is made arbitrary small by a control, only boundedness of the cavity fields of each TITO subsystem is guaranteed. In this paper, the properties of the TITO and the TIMO cavity RF systems are investigated.

THPPD002

The First Magnetic Field Control (B-Train) to Optimize the Duty Cycle of a Synchrotron in Clinical Operation

controls, synchrotron, extraction, pick-up

3503

E. Feldmeier, R. Cee, M. Galonska, Th. Haberer, A. Peters, S. Scheloske
HIT, Heidelberg, Germany

In December 2011 the Heidelberg Ion Therapy Center started to use the magnetic field feedback control for its clinical operation. Therewith the magnetic field deviation of the ramped magnets in the synchrotron depending on eddy currents and hysteresis are no longer in effect. Waiting times on the flattop and the "chimney" in the recovery phase of the synchrotron cycle are no longer necessary. The efficiency of the accelerator is increased by more than 20\% and the treatment time shortens accordingly. The core of the magnetic feedback system is a real time measuring system of the magnetic field with extremely high precision.

THPPD014

Design and Performance of Various kinds of Corrector Magnets for the Taiwan Photon Source

booster, vacuum, simulation, power-supply

3524

C.Y. Kuo, C.-H. Chang, M.-H. Huang, C.-S. Hwang, J.C. Jan, F.-Y. Lin
NSRRC, Hsinchu, Taiwan

Three types of DC corrector magnets will be installed in the booster ring (BR), LINAC to booster (LTB) and booster to storage ring (BTS) in the Taiwan photon source (TPS). These DC corrector magnets have different gap sizes, iron lengths and field strengths for different bending angles to optimize the electron beam. The DC magnetic fields are simulated by TOSCA 2D/3D static field analysis and optimum processes are discussed. An AC steering fast feedback corrector (FFC) combines horizontal and vertical dipole fields for the fast feedback correction in the storage ring (SR). The field variation with the alternating current in the 300Hz frequency of the FFC magnet is simulated by the Opera 3d ELEKTRA/SS analysis module to estimate the operating current. This paper will be presented about features, design concept and results of field measurement of these corrector magnets.
NSRRC, 10¹ Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan

THPPD025

Expected and Measured Behaviour of the Tune in the LHC Operation at 3.5 TeV

injection, quadrupole, dipole, betatron

3554

N. Aquilina
CERN, Geneva, Switzerland

The tune of the Large Hadron Collider depends on the strength of the quadrupole magnets, the b2 component in the main dipoles plus the b3 component in the main dipoles and the sextupolar correctors via feed down in case of systematic misalignment. The magnetic model of the machine, based on a fit of magnetic measurements, has an intrinsic precision which can be estimated in a few units. During the first years of operation of the LHC, tune has been routinely measured and corrected through a feedback system. In this paper we reconstruct from the beam measurements and the settings of the feedback loop the evolution of tune during injection, ramp, and squeeze. This gives the obtained precision of the magnetic model of the machine with respect to quadrupolar and sextupolar components. At the injection plateau there is an unexpected large decay whose origin is not understood: we present the data, with the time constants and the dependence on the previous cycles, and compare to the magnetic measurements. During the ramp the tune drifts by about 0.05: this precision is related to the precision in tracking the quadrupolar field in the machine.

THPPD062

Development of Digital-controlled Corrector Magnet Power Converter with Shunt as a Current Sensing Component

controls, power-supply, simulation

3653

B.S. Wang, J.C. Huang, K.-B. Liu
NSRRC, Hsinchu, Taiwan

In Taiwan light source (TLS), Bira MCOR power converter modules are adopted as the corrector magnet power converters, the output is regulated by analog PWM IC that caused nonlinear behavior at zero cross and the adjustment of compensator for difference kind of magnet load is inconvenient. In the thesis the analog regulation IC is replaced by a fully digital regulation control circuit to realize digital regulation control converter. With plugging the home-made fully DSP regulation control cards into MCOR30 that the current sensing component is a shunt, the switching losses of MOSFET was reduced and the cost that the component of current sense. With the fully digital regulation control circuit, the parameter of the compensator for different magnet load is very easy to adjustment. In addition, the feasibility and validity of MOSFET switching theorem is simulated with Matlab simulink and the performance of this power converter is verified, the output current ripple of this power converter could be lower than 10ppm, which is beyond the requirement of current TLS corrector power converter and qualified to be used in the future TPS facility.

THPPD064

The Compensator Design of the Fully Digital Controlled Corrector Magnet Power Converter by Using LabView as the Development Tools

controls, LabView, power-supply

3659

B.S. Wang, J.C. Huang, K.-B. Lin
NSRRC, Hsinchu, Taiwan

The auto-tuning of PI-compensator for power converter is fulfilled by using the LabVIEW. The current error signals of the power converter with different PI compensating parameters are transferred by RS-232 or Ethernet communication interface from DSP card into LabVIEW and FFT analysis are calculated. The FFT analysis are stored in the batch file for further numerical analysis and the parameters with the best response is recognized which will be set as the default PI parameters. In addition, the feasibility and validity of auto-tuning theorem was verified by measuring the long-term stability of output current and during the long-term measuring period the stability and ripple current of the power converter are observed. In this thesis, the fully digital regulation controlled corrector magnet power converter with a shunt as the current sensing component was used as the developing platform. The auto-tuning theorem was realized and applied to the compensator of the power converter, and the best output current response of the power converter was fulfilled.

THPPD066

High Precision Programmable of TPS Quadrupole Magnet Power Supply

controls, power-supply, quadrupole, synchrotron

3662

Y.S. Wong, J.C. Huang, K.-B. Liu, W.S. Wen
NSRRC, Hsinchu, Taiwan

In 1993, the first of Taiwan light source was held on October 16. First beam stored in the storage ring and facility at synchrotron radiation research centre (SRRC) was opened to users and the full energy injection to 1.5Gev after seven years. In 2007, the president of Executive Yuan Taiwan had been announcement to set up a third-generation synchrotron radiation. Taiwan Photon Source (TPS) project total budget of NT6, 885 million from 2007~ 2013. TPS project will improve technical capability to build to3.3Gev electron energy. Totally had been installed 1032sets of magnet power supplies for the storage ring and 152 sets for the injector. In the future, Taiwan photon source set up complete and operation, it will offer one of the world's brightest synchrotron x-ray sources.

THPPD073

Development and Management of the Modulator System for PLS-II 3.0 GeV Electron Linac

controls, power-supply, linac, klystron

3683

S.H. Kim, J.Y. Huang, S.J. Kwon, B.-J. Lee, Y.J. Moon, S.H. Nam, S.S. Park, S. Shin
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: This work is supported by MEST(Ministry of Education, Science and Technology) and POSCO(Pohang Steel and Iron Company).
The Pohang Accelerator Laboratory (PAL) had started the upgrade project (called PLS-II) of the Pohang Light Source (PLS) from 2009 for increasing its energy from 2.5 GeV to 3 GeV and changing the operation mode from fill-up to top-up mode. Top-up mode operation requires high energy stability of the linac beam and machine reliability in the linac modulator systems. For providing the additional 0.5 GeV energy from the 2.5 GeV PLS linac, we added four units of the modulator system. We have two different types of the pulse modulator system for using existing pulse modulators, thyristor control type, in the upgrade project (PLS-II). The two types are thyristor control type and inverter power type. In the thyristor control type, a de-Qing system controls the modulator pulse forming network (PFN) charging voltage stability, and in the inverter power supply type, CCPS provides highly stable charging voltage to the modulator. We will present development and management of the pulse modulator system for obtaining machine reliability and stability from 3.0 GeV linac.

THPPP010

LHC Orbit Correction Reproducibility and Related Machine Protection

controls, status, luminosity, injection

3746

K. Fuchsberger, T. Baer, R. Schmidt, J. Wenninger
CERN, Geneva, Switzerland

The Large Hadron Collider (LHC) has an unprecedented nominal stored beam energy of up to 362 MJ per beam. In order to ensure an adequate machine protection by the collimation system, a high reproducibility of the beam position at collimators and special elements like the final focus quadrupoles is essential. This is realized by a combination of manual orbit corrections, feed forward and real time feedback. In order to protect the LHC against inconsistent orbit corrections, which could put the machine in a vulnerable state, a novel software-based interlock system for orbit corrector currents was developed. In this paper, the principle of the new interlock system is described and the reproducibility of the LHC orbit correction is discussed against the background of this system.

THPPP011

Studies on a Wideband, Solid-state Driven RF System for the CERN PS Booster

impedance, cavity, acceleration, booster

3749

M.M. Paoluzzi, L. Arnaudon, N. Chritin, M. Haase, K. Hanke, B. Mikulec, T. Tardy
CERN, Geneva, Switzerland

In the framework of the LHC Injectors Upgrade project (LIU) the PS Booster (PSB) RF systems will undergo in depth consolidation and upgrade programs. The aim is increasing the extraction energy to 2 GeV and allowing reliable operations during next 25 years. Substantial improvements could come from the replacement of the existing narrowband, tuned systems covering the h=1 and h=2 frequency ranges (0.6 / 1.8 MHz and 1.2 / 3.6 MHz respectively) with wideband (0.5 / 4 MHz) Finemet® loaded cavities. The new system would be modular, allow multi-harmonic operation, use solid-state power stages and include fast RF feedback to compensate beam loading effects to some extent. A prove of principle system providing ≈3.0 kV accelerating voltage has been designed, constructed and installed in one of the PSB rings. This paper provides details on the design and measurements as well as information on the project status.

THPPP047

The ESS Control Box

controls, EPICS, target, neutron

3844

E. Laface
ESS, Lund, Sweden
M. Reščič
Cosylab, Ljubljana, Slovenia

The European Spallation Source will be a 5 MW superconducting proton linac, with fixed target, for the production of a stream of neutrons. The entire machine, the target and all the instruments will be controlled by an Integrated Control System: this is a set of hardware and software tools created to provide the most possible easy and flexible interface for the operator daily usage in the control room. The hardware core of the Integrated Control System is the Control Box, a Linux-based computer designed to provide a common platform for the ESS hardware developers. The software front-end for the Control Box is the Experimental Physics and Industrial Control System - EPICS, a standard protocol used to control large facilities such as accelerators or nuclear power plants. In this paper the main characteristics of the Control Box and the EPICS system are presented.

THPPR010

Integrate EPICS System with the TLS Control System

EPICS, controls, synchrotron, status

3984

Y.-S. Cheng, Y.-T. Chang, J. Chen, P.C. Chiu, K.T. Hsu, K.H. Hu, C.H. Kuo, C.Y. Liao, C.Y. Wu
NSRRC, Hsinchu, Taiwan

The TLS (Taiwan Light Source) is a third generation of synchrotron light source, and it has been operated since 1993. The TLS control system was developed and implemented by ourselves. The control system of our new project (TPS, Taiwan Photon Source) is developed and based upon the EPICS framework. To earn more experiences on the EPICS usage, some of the TLS newly installed subsystem run EPICS directly. For example, BPM system, bunch-by-bunch feedback system, remote oscilloscope waveform access and so on adapt the EPICS interface to control and monitor. The EDM and Matlab (with LabCA) toolkits are used as EPICS graphical user interface, and it is also operated at the TLS control consoles environment normally. The archive system transaction between the TLS control system format and EPICS PVs (Process Variables) has been implemented for user access with the existing archive viewer. The efforts will be described at this report.

THPPR014

FRIB High-level Software Architecture

controls, EPICS, monitoring, optics

3996

P. Chu, T.D. Brown, R. Gaul, S. Peng
FRIB, East Lansing, Michigan, USA
E.T. Berryman, V. Vuppala
NSCL, East Lansing, Michigan, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The Facility for Rare Isotope Beams (FRIB) is setting up its high-level application software architecture. The architecture is based on Service Oriented Architecture, and consists of back-end data storage, client/service infrastructure, control system connectivity, supporting libraries and front-end Graphical User Interface (GUI). The architecture provides online models of FRIB as a service and allows for storage of both structured and non-structured data. The model for structured data is implemented using the Integrated Relational Model of Installed Systems (IRMIS). The GUI is based on Control System Studio (CSS) framework. Libraries, service, data access and GUI tools will be available as Application Programming Interface (API) or plug-ins. The infrastructure and technologies chosen here will utilize the robustness and performance for applications, as well as support quick prototyping for physicists. This paper describes FRIB’s high-level application software architecture and some of the current prototypes.

THPPR039

Controlled Transverse Blow-Up of High-energy Proton Beams for Aperture Measurements and Loss Maps

injection, emittance, resonance, proton

4059

W. Höfle, R.W. Assmann, S. Redaelli, R. Schmidt, D. Valuch, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland

A technique was developed to blow-up transversely in a controlled way high energy proton beams in the LHC. The technique is based on band limited white noise excitation that is injected into the transverse damper feedback loop. The injected signal can be gated to selectively blow-up individual trains of bunches. The speed of transverse blow-up can be precisely controlled. This opens the possibility to perform safely and efficiently aperture measurements and loss maps with high intensity bunch trains well above stored beam energies that are considered to be safe. In particular, lengthy procedures for measurements at top energy, otherwise requiring multiple fills of individual bunches, can be avoided. In this paper, the method is presented and results from beam measurements are discussed and compared with alternative blow-up methods.

THPPR040

First Operational Experience with the LHC Machine Protection System when Operating with Beam Energies Beyond the 100 MJ Range

injection, luminosity, monitoring, interlocks

4062

M. Zerlauth, R.W. Assmann, B. Dehning, M. Ferro-Luzzi, B. Goddard, M. Lamont, R. Schmidt, A.P. Siemko, J.A. Uythoven, J. Wenninger
CERN, Geneva, Switzerland

The LHC made a remarkable progress in luminosity production during 2011 operation. This was made possible by a progressive increase of beam intensities by more than 5 orders of magnitude, reaching stored beam energies beyond 100MJ at the end of the year. The correct functioning of the machine protection systems was vital during initial operation and even more when approaching nominal beam parameters, where an uncontrolled loss of a small fraction of the beam is already sufficient to damage accelerator equipment or the large experimental detectors The machine protection system depends on the interplay of many different elements: beam dumping system, beam interlocks, beam instrumentation, equipment monitoring, collimators and absorbers, etc. The strategy applied during 2011 to allow for an efficient but yet safe increase of the beam intensities is presented along with the associated risks and drawbacks of a too aggressive approach. The experience gained with the key systems will be discussed along with possibilities to further enhance machine availability whilst maintaining the current level of safety.