Keyword: feedback
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MOYAB101 The First Years of LHC Operation for Luminosity Production luminosity, proton, injection, emittance 6
 
  • M. Lamont
    CERN, Geneva, Switzerland
  
  A summary of the first 3 years of LHC operation is presented with a discussion on the performance ramp-up, operation efficiencies and system reliability. The main contributory factors to peak and integrated luminosity performance are outlined.  
slides icon Slides MOYAB101 [12.139 MB]  
 
MOPEA006 Operation and Performance Upgrade of the SOLEIL Storage Ring vacuum, power-supply, dipole, injection 73
 
  • A. Nadji, F. Bouvet, P. Brunelle, A. Buteau, L. Cassinari, M.-E. Couprie, N. Hubert, M. Labat, J.-F. Lamarre, P. Lebasque, A. Lestrade, A. Loulergue, P. Marchand, J.L. Marlats, L.S. Nadolski, R. Nagaoka, M.-A. Tordeux
    SOLEIL, Gif-sur-Yvette, France
  
  SOLEIL delivers photons to 26 beamlines and 3 new ones are under construction together with the femtoslicing project. Up to 5 filling patterns are available for the users including a low alpha mode; all of them are in Top-up injection. The beam current for the users has been increased to 430 mA in the multibunch mode. The Storage Ring (SR) is running with a new optics incorporating an additional quadrupole triplet in one long straight section. The beam position stability remains excellent. Vertical positions from the dipole X-BPMs have been included in the orbit feedbacks loop with very encouraging results. A feedback loop maintaining the emittance coupling close to 1% for any Insertion Devices (IDs) configuration has been implemented. Up to 25 very diverse IDs are now installed on the SR, and several others are under design or construction. In house developments are being carried out in several domains such as construction of SR dipole power supply spare and of 70 kW-500 MHz solid state amplifiers, design of a pulsed multipole magnet for injection, and a Robinson wiggler, as well as a feasibility study of a local reduction of the emittance in one of the long straight sections.  
 
MOPEA055 First Year Operation of the ALBA Synchrotron Light Source vacuum, storage-ring, interlocks, kicker 202
 
  • F. Pérez
    CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
  
  ALBA is a 3 GeV, 3rd generation, light source located in Cerdanyola, Barcelona, Spain, which started users operation in May 2012. In this paper we will report about the transition from commissioning to operation, the main problems faced during this first year, the actual status of the accelerators and we will provide an outlook to the next steps.  
 
MOPEA071 Operating the Diamond Storage Ring with Reduced Vertical Emittance emittance, coupling, target, storage-ring 249
 
  • I.P.S. Martin, M.G. Abbott, M. Apollonio, R. Bartolini, D. Hickin
    Diamond, Oxfordshire, United Kingdom
  • R. Bartolini
    JAI, Oxford, United Kingdom
  
  In a synchrotron radiation light source, a reduction in vertical emittance can potentially increase the source brightness, reduce the spot size for microfocus beam lines or increase the vertical transverse coherence of the photon beam. With this aim, the target vertical emittance for the Diamond storage ring has been recently reduced from 27pm.rad to 8pm.rad (0.3% coupling). In this paper we discuss the main impacts of this reduction, along with the steps that have been taken to stabilise the coupling at the new value.  
 
MOPEA077 Accelerator Physics and Light Source Research Program at Duke University FEL, wiggler, storage-ring, electron 264
 
  • 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.
he accelerator physics and light source research program at Duke Free-Electron Laser Laboratory (DFELL), TUNL, is focused on the development of the storage ring based free-electron lasers (FELs), and a state-of-the-art Compton gamma-ray source, the High Intensity Gamma-ray Source (HIGS). Driven by the storage ring FEL, the HIGS is world's most intense Compton gamma-ray source with a maximum total flux of few 1010 gamma per second (around 10 MeV). Operated in the energy range from 1 to 100 MeV, the HIGS is a premier nuclear physics research facility in the world. In 2012, we completed a major accelerator upgrade project with a wiggler switchyard system which allows the configuration changes between planar and helical FEL wigglers, and a great enhancement of the FEL gain when operated with 3 or 4 helical wigglers. In this paper, we will describe our ongoing light source development to produce gamma-ray beams in the new energy range of 100 and 158 MeV. We will also provide a summary of our accelerator physics research activities in the area of nonlinear dynamics, beam instability research, and FEL research. 		 
 
MOPME008 Beam Diagnostics by Using Bunch-by-bunch Feedback Systems at the DELTA Storage Ring injection, kicker, laser, electron 485
 
  • M. Höner, H. Huck, M. Huck, S. Khan, R. Molo, A. Schick, P. Ungelenk
    DELTA, Dortmund, Germany
  
  Funding: Work supported by BMBF (05K10PEB)
At DELTA, a 1.5-GeV electron storage ring operated by the TU Dortmund University, longitudinal and transverse bunch-by-bunch feedback systems are in use to detect and suppress multi-bunch instabilities. Besides that, the digital feedback systems are excellent diagnostics tools. As an example, by exciting a certain number of bunches within the bunch train, the coupling to the non-excited bunches can be investigated below and above the instability threshold. Other examples include studies of the injection process and monitoring bunch oscillations during sudden beam loss. First experimental results will be presented in this paper. 		 
 
MOPWA001 Development of a High Precision Integrator for Analog Signals to Measure Magnetic Fields in Realtime pick-up, synchrotron, ion, controls 661
 
  • E. Feldmeier, Th. Haberer
    HIT, Heidelberg, Germany
  
  For the Magnetic Field Control of the synchrotron at the Heidelberg Ion Therapy Centre the magnetic fields are measured with a pickup coil along the beam pipe. The induced pickup voltage, corresponding to changes in the magnetic field, has to be integrated in realtime to determine the actual field. A high precision integrator has been developed to measure fields with an accuracy of 4ppm over 10 seconds. This new integrator has a very low drift and calibrates during the measurement. It is the fastest and most accurate integrator for integrating analoge voltages in realtime.  
 
MOPWA002 New Purposed High Precision Power Supply For Quadrupole Magnets Of ILSF using Low Resolution Digital PWM power-supply, quadrupole, storage-ring, controls 664
 
  • M. Jafarzadeh, M. Akbari, J. Rahighi, D. Shirangi, E.H. Yousefi
    ILSF, Tehran, Iran
  
  A total number of 104 quadrupole magnets, split into 9 families, will be required for the ISLF storage ring lattice. Each quadrupole magnet is connected with its own independent power supply. In new design for quadrupole magnets, the outputs of two synchronized push-pull converters (one for coarse regulation and another for fine current regulation) will be added together before a synchronous rectification. In this manner, there will be no need for extra high-current electronic parts. Another advantage of this design is using a high-voltage inductor on the switching side rather than a high current inductor ion the high current side. The PWM signal to control of buck converter (at the input stage of each unit) will be generated inside a dsPIC .  
 
MOPWA005 Development of a Feedback Control System for Resonant Power Supplies in the J-PARC 3-GeV Synchrotron controls, power-supply, impedance, quadrupole 672
 
  • Y. Watanabe
    JAEA, Ibaraki-ken, Japan
  • N. Tani
    JAEA/J-PARC, Tokai-mura, Japan
  
  In the J-PARC 3-GeV Synchrotron, dipole magnets and seven families of quadrupole magnets are excited with a DC-biased 25 Hz sinusoidal waveforms using an individual resonant circuits. This paper proposed a feedback system to improve the amplitude and phase stability, specially against variation of capacitance caused by temperature characteristics in the resonant circuits. The control system has been successfully demonstrated and achieved amplitude and phase stability under ±0.005% and ±0.5 uS, respectively.  
 
MOPWA006 Magnet Power Supply with Small Ripple using Sub-converter and Symmetrical Structure power-supply, controls, sextupole, extraction 675
 
  • S. Nakamura
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • S. Yamada
    KEK, Tokai, Ibaraki, Japan
  
  High precision tracking and small current ripple are necessary for a magnet power supply of a high power accelerator. A prototype power supply of the 100kW class is developed with an aim of small current ripple less than 10ppm, which employs a combination of main and sub-converter with symmetrical structure. The main converter unit supplies pattern current by a voltage feedforward control, while the sub-converters by a current feedback control. The symmetrical structure of the power supply is adopted to decouple normal mode and common mode ripples. Each converter unit is modularized and surrounded by a Faraday cage suppress for suppressing radiation of electrical noise and ease for maintenance. Its performance is studied using a set of 24 units of setupole magnets installed in J-PARC Main Ring.  
 
MOPWA014 Research and Design of Digital Power Supply for  HIRFL-RIBLL Corrector Magnet power-supply, controls, secondary-beams, ion 690
 
  • Y.Z. Huang, Y.X. Chen, D.Q. Gao, J.B. Shangguan, R.K. Wang, H.H. Yan, Z.Z. Zhou
    IMP, Lanzhou, People's Republic of China
  
  One digital power supply was designed for RIBLL (Radioactive Ion Beam Line in Lanzhou) corrector magnet at HIRFL (Heavy Ion Research Facility in Lanzhou). Adopting two parallel connected IGBT full-bridges as the power circuit topology, the power supply can generate bipolar DC current when it runs in the fourquadrant working states, which well meets the requirements of corrector magnet. SOPC platform of Altera based on Nios II is chosen to design the digital power supply regulator. Employing FPGA as the control core and utilizing SOPC principles, the digital regulator is designed against special requirements of accelerator power supply. The test results indicate that performance of the power supply can meet the design requirements.  
 
MOPWA025 2Hz Ramping Mode Dipole Power Supply for Testing the NSLSII Booster Dipole Magnets power-supply, dipole, booster, controls 714
 
  • A.I. Erokhin, A.V. Bulatov, K. Gorchakov, S.M. Gurov, V.V. Kolmogorov, A.A. Kremnev, D.N. Pureskin, D.V. Senkov, R.V. Vakhrushev
    BINP SB RAS, Novosibirsk, Russia
  
  Budker Institute has designed and delivered Booster for NSLSII project including vacuum system, magnet system, diagnostics and power supplies. Dipole power supplies were directly delivered to BNL by sub-contractor (Danfysik, Denmark). To test dipole magnets on factory side, at BINP, it was decided to design and construct a high current ramping mode power supply. The designed power supply can operate with the reactive output power up to 150kVA and output current up to 900A at 2Hz ramping mode. The absolute accuracy achieved is better than 100ppm for the injection and extraction flats and better than 500ppm for the ramps.  
 
MOPWA047 Development of a Digital Control Interface Card with a LabVIEW Control Program for TLS Corrector Magnet Power Supply controls, LabView, power-supply, monitoring 777
 
  • B.S. Wang, K.-B. Liu
    NSRRC, Hsinchu, Taiwan
  
  This paper presents an implementation of a virtual instrument control interface and a digitally controlled interface card for Taiwan Light Source (TLS) corrector magnet power supplies (MPS). Eight pieces of corrector MPS converter module are monitored and controlled by the digitally controlled interface card with delimit boundary of ±10 voltage. The digitally controlled interface card was implemented with an ADS1278 24-bits multi-channel analog-to-digital converter、a DAC8718 16-bits multi-channel digital-to-analog converter and the TMS320F28335 digital signal processor. There are two control modes of the virtual instrument control interface, which are 1) local control mode by RS-232, 2) the remote control by MiiNePort\E1 TCP/IP protocol; with the developed Labview control interface the user can choose which mode to communicate with the corrector magnet power supplies depending on the working environment.  
 
MOPWA057 Development of a High-resolution, Broad-band, Stripline Beam Position Monitoring System monitoring, linear-collider, controls, extraction 804
 
  • G.B. Christian, D.R. Bett, N. Blaskovic Kraljevic, P. Burrows, M.R. Davis, Y.I. Kim, C. Perry
    JAI, Oxford, United Kingdom
  • R. Apsimon, B. Constance
    CERN, Geneva, Switzerland
  • P. Burrows, C. Perry
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
  • J. Resta
    IFIC, Valencia, Spain
  
  A low-latency, sub-micron resolution stripline beam position monitoring system has been developed and tested with beam at the KEK Accelerator Test Facility, where it has been used as part of a feedback system for beam stabilisation. The fast analogue front-end signal processor is based on a single-stage down-mixer and is combined with an FPGA-based system for digitisation and feedback control. A resolution as low as 400 nm has been demonstrated for beam intensities of ~1 nC, with single-pass beam. The latest results of recent modifications to balance the input path lengths to the processor will be discussed. These modifications compensate for the inherent phase sensitivity of the processors, and hence improve the intrinsic resolution, without the need for offline correction. Modifications to the FPGA firmware will also be described, to allow for flexible operation with variable system-synchronous data acquisition at up to 400 MHz, with up to nine data channels of 13-bit width, and a nominal record length of 1 KS/channel/pulse (extensible to a total record length of 120 KS per pulse, for example, for use with long bunch trains or wide-band multi-turn measurements in storage rings).  
 
MOPWA058 Cavity Beam Position Monitor at Interaction Point Region of Accelerator Test Facility 2 cavity, quadrupole, optics, focusing 807
 
  • Y.I. Kim, D.R. Bett, N. Blaskovic Kraljevic, P. Burrows, G.B. Christian, M.R. Davis, A. Lyapin
    JAI, Oxford, United Kingdom
  • S.T. Boogert
    Royal Holloway, University of London, Surrey, United Kingdom
  • J.C. Frisch, D.J. McCormick, J. Nelson, G.R. White
    SLAC, Menlo Park, California, USA
  • Y. Honda, T. Tauchi, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  
  Nanometre resolution cavity beam position monitors (BPMs) have been developed to measure the beam position and linked to a feedback system control the beam position stability within few nanometres in the vertical direction at the focus, or interaction point (IP), of Accelerator Test Facility 2 (ATF2). In addition, for feedback applications a lower-Q and hence faster decay time system is desirable. Two IPBPMs have been installed inside of IP chamber at the ATF2 focus area. To measure the resolution of IPBPMs two additional C-band cavity BPMs have been installed one upstream and one downstream of the IP. One cavity BPM has been installed at an upstream image point of IP. The performance of the BPMs is discussed and the correlation between IP and image point positions is presented along with a discussion of using these BPMs for position stabilisation at the IP.  
 
MOPWA074 High Voltage Converter Modulator Optimization high-voltage, controls, neutron, background 852
 
  • A. Scheinker
    LANL, Los Alamos, New Mexico, USA
  • M.J. Bland
    University of Nottingham, Nottingham, United Kingdom
  
  High voltage converter modulators (HVCM) are at the forefront of long pulse high voltage (100kV) technology for Klystron voltage sources. We present results of digitally implementing an extremum seeking (ES) algorithm with which we optimized the rise time of the output voltage of a HVCM at the Los Alamos Neutron Science Center (LANSCE) HVCM test stand by iteratively, simultaneously tuning the first 8 switching edges of each of the three phase drive waveforms (24 variables total). We achieved a 50us rise time, which is reduction in half compared to the 100us currently achieved at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. The ES algorithm is successful despite the noisy measurements and cost calculations, confirming the theoretical predictions that the algorithm is not affected by noise unless it both matches exactly the frequency components of the controller's specific perturbing frequencies and is of comparable size.  
 
MOPWO087 Parameter Estimation of the Exponentially Damped Sinusoid for Noisy Signals closed-orbit, neutron, damping, synchrotron 1079
 
  • T.A. Pelaia
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725
The damped sinusoid equation is a common model for many scientific processes involving damped periodic signals. Here we present two methods for estimating the damped sinusoid parameters for noisy signals. Both methods are based upon an exact, closed form solution to fit the parameters for signals without noise, and they estimate the parameters for the noisy signals by the statistical maximum likelihood criterion. The first method relies on an optimizer to minimize the mean square signal error. The second method estimates the parameters by direct calculation and is suitable when the signal noise is small and the frequencies are sufficiently far from the integer and half integer values. 		 
 
TUOCB202 Fast Orbit Feedback Scheme and Implementation for Taiwan Photon Source power-supply, simulation, controls, EPICS 1146
 
  • P.C. Chiu, K.T. Hsu, K.H. Hu, C.H. Kuo, C.Y. Wu
    NSRRC, Hsinchu, Taiwan
  
  TPS (Taiwan Photon Source) is a 3 GeV synchrotron light source which is being in construction at NSRRC. As most of 3rd generation light sources, the fast orbit feedback system would be adopted to eliminate various disturbances and improve orbit stability. Due to the vacuum chamber material made of aluminum with higher conductivity and lower bandwidth, both of slow and fast correctors will be used for FOFB correction. In general, there are two schemes to operate these hybrid correctors. One is to transfer correction from fast to slow correctors periodically and avoid fast corrector saturation. The other is the fast correctors operated only at higher frequency domain and slow ones take care of DC part. TPS would adopt the first scheme but the second one still as a substitute. Both schemes will be supported. This report summarizes the infrastructure of the FOFB and the simulation is also presented.  
slides icon Slides TUOCB202 [3.035 MB]  
 
TUOCB203 In Vacuum High Accuracy Mechanical Positioning System of Nano Resolution Beam Position Monitor at the Interaction Point of ATF2 vacuum, alignment, linear-collider, collider 1149
 
  • P. Bambade, O.R. Blanco, F. Bogard, P. Cornebise, S. Wallon
    LAL, Orsay, France
  • T. Tauchi, N. Terunuma
    KEK, Ibaraki, Japan
  
  ATF2 is a low energy (1.3GeV) prototype of the final focus system for ILC and CLIC linear collider projects. A major goal of ATF2 is to demonstrate the ability to stabilise the beam position at the interaction point, where the beam can be focused down to about 35 nm. For this purpose, a set of new Beam Position Monitors (BPM) has been designed, with an expected resolution of about 2 nm. These BPMs must be very well aligned with respect to the beam, at the few micron level, to fully exploit their fine resolution. In this paper, the mechanical positioning system which has been developed to enable such a precise alignment is presented. It is based on a set of eight piezo actuators with nanometer range displacement resolution, mounted in a new specially made vacuum chamber. Due to the expected resolution of the piezo actuators, this system also brings a new functionality, the possibility to calibrate the BPMs by mechanically scanning the beam.  
slides icon Slides TUOCB203 [2.276 MB]  
 
TUPFI035 Head-on and Long range Beam-beam Interactions in the LHC: Effective Tune Spread and Beam Stability due to Landau Damping octupole, damping, luminosity, lattice 1421
 
  • X. Buffat
    EPFL, Lausanne, Switzerland
  • W. Herr, N. Mounet, E. Métral, T. Pieloni
    CERN, Geneva, Switzerland
  
  We discuss the Landau damping of coherent instabilities in the presence of betatron tune spread. This tune spread can originate from dedicated non-linear magnets such as octupoles, or through the beam-beam interaction. In the latter case we have to distinguish the contribution from head-on and parasitic beam-beam interactions and the collision pattern of different bunches plays an important role. The interplay of these sources of tune spread and the resulting stability is discussed for the case of the LHC.  
 
TUPFI040 Experimental Verification of the CLIC Two-Beam Acceleration Technology in CTF3 linac, acceleration, collider, bunching 1436
 
  • P. Skowroński, A. Andersson, J. Barranco, B. Constance, R. Corsini, S. Döbert, A. Dubrovskiy, W. Farabolini, E. Ikarios, R.L. Lillestøl, T. Persson, F. Tecker
    CERN, Geneva, Switzerland
  • W. Farabolini
    CEA/DSM/IRFU, France
  • E. Ikarios
    National Technical University of Athens, Athens, Greece
  • M. Jacewicz, A. Palaia, R.J.M.Y. Ruber
    Uppsala University, Uppsala, Sweden
  • R.L. Lillestøl
    University of Oslo, Oslo, Norway
  • T. Persson
    Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden
  
  The Compact Linear Collider (CLIC) International Collaboration is pursuing an extensive R&D program towards a multi-TeV electron-positron collider. In particular, the development of two beam acceleration technology is the focus of the CLIC test facility CTF3. In this paper we summarize the most recent results obtained at CTF3: the results of the studies on the drive beam generation are presented, the achieved two beam acceleration performance is reported and the measured break-down rates and related observations are summarized. The stability of deceleration process performed over 13 subsequent modules and the comparison of the obtained results with the theoretical expectations are discussed. We also outline and discuss the future experimental program.  
 
TUPFI082 RHIC Performance for FY2012 Heavy Ion Run ion, luminosity, booster, heavy-ion 1538
 
  • Y. Luo, J.G. Alessi, M. Bai, E.N. Beebe, J. Beebe-Wang, I. Blackler, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, J.J. Butler, R. Connolly, T. D'Ottavio, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, D.M. Gassner, X. Gu, Y. Hao, M. Harvey, T. Hayes, L.T. Hoff, H. Huang, P.F. Ingrassia, J.P. Jamilkowski, N.A. Kling, M. Lafky, J.S. Laster, C. Liu, D. Maffei, Y. Makdisi, M. Mapes, G.J. Marr, A. Marusic, F. Méot, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, C. Naylor, S. Nemesure, A.I. Pikin, P.H. Pile, V. Ptitsyn, D. Raparia, G. Robert-Demolaize, T. Roser, P. Sampson, J. Sandberg, V. Schoefer, C. Schultheiss, F. Severino, T.C. Shrey, K.S. Smith, S. Tepikian, P. Thieberger, D. Trbojevic, J.E. Tuozzolo, B. Van Kuik, G. Wang, M. Wilinski, A. Zaltsman, K. Zeno, S.Y. Zhang, W. Zhang
    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 the 2012 RHIC heavy ion run, we collided 96.4~GeV U-U ions and 100~GeV Cu-Au ions for the first time in RHIC. The new pre-injector with the electron-beam ion source (EBIS) was used to provide ions for RHIC ion collisions for the first time. By adding the horizontal cooling, the powerful 3-D stochastic cooling largely enhanced the luminosity. With the double bunch merging in the Booster and AGS, the bunch intensities of Cu and Au ions in RHIC surpassed their projections. Both PHENIX and STAR detectors reached their integrated luminosity goals for the U-U and Cu-Au collisions. In this article we review the machine improvement and performance in this run. 		 
 
TUPME051 CLIC Final Focus System Alignment and Magnet Tolerances luminosity, quadrupole, sextupole, linear-collider 1682
 
  • J. Snuverink, J. Barranco, H. Garcia, Y.I. Levinsen, D. Schulte, R. Tomás
    CERN, Geneva, Switzerland
  
  The design requirements for the magnets in the Compact Linear Collider (CLIC) Final Focus System (FFS) are very stringent. In this paper the sensitivity for the misalignment and the magnetic imperfections for the different magnets in the FFS and the crab cavity are presented. Possible mitigation methods are discussed.  
 
TUPWA009 Bunch by Bunch Intra-Bunch Feedback System for Curing Transverse Beam Instabilities at the J-PARC MR impedance, injection, kicker, betatron 1739
 
  • O. A. Konstantinova, Y.H. Chin, Y. Kurimoto, T. Obina, M. Okada, K. Takata, M. Tobiyama, T. Toyama
    KEK, Ibaraki, Japan
  • Y. Shobuda
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  
  At the J-PARC Main Ring (MR), transverse instabilities have been observed during the injection and at the onset of acceleration with large particle losses. The present bunch by bunch feedback system, operating in a narrowband mode, has been effectively suppressing these instabilities, allowing the beam power to reach 230kW with only 400W of particle losses. The observed beam signals show that bunches are still executing complicated intra-bunch oscillations even if the narrowband feedback system is on, though they are not imposing significant particle losses at present. The new and more advanced broadband feedback system has been developed for control of the intra-bunch oscillations and further reduction of particle losses. The elaborate analysis code has been also developed on the MATLAB platform to analyse effects of the broadband feedback system on intra-bunch oscillations. This paper describes the development of these advanced instruments and presents the analysis of the latest beam test results using the MATLAB code.  
 
TUPWA044 Longitudinal Coupled-Bunch Oscillation Studies in the CERN PS damping, kicker, cavity, emittance 1808
 
  • H. Damerau, S. Hancock, M.M. Paoluzzi
    CERN, Geneva, Switzerland
  • M. Migliorati, L. Ventura
    Rome University La Sapienza, Roma, Italy
  
  Longitudinal coupled-bunch oscillations are an important limitation for the high-brightness beams accelerated in the CERN PS. Up to the present intensities they are suppressed by a dedicated feedback system limited to the two dominant oscillation modes. In view of the proposed installation of a wide-band feedback kicker cavity within the framework of the LHC Injectors Upgrade project (LIU), measurements have been performed with the existing damping system with the aim of dimensioning the new one. Following the excitation of well-defined oscillation modes, damping times and corresponding longitudinal kick strength are analysed. The paper summarizes the results of the observations and gives an outlook on the expected performance with the new coupled-bunch feedback.  
 
TUPWA061 Observation at CesrTA of the Reduction of the Vertical Beam Size of the Lead Bunch in a Train Due to the Presence of a Precursor Bunch electron, positron, dipole, simulation 1841
 
  • M.G. Billing, K.R. Butler, G. Dugan, M.J. Forster, R.E. Meller, G. Ramirez, N.T. Rider, K.G. Sonnad, H.A. Williams
    CLASSE, Ithaca, New York, USA
  • J.W. Flanagan
    KEK, Ibaraki, Japan
  • R. Holtzapple, M. Randazzo
    CalPoly, San Luis Obispo, California, USA
  • M.A. Palmer
    Fermilab, Batavia, USA
  
  Funding: Work supported by DOE Award DE-FC02-08ER41538, NSF Award PHY-0734867, PHY-1068662 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 make use of instrumentation for the detection of the coherent self-excited spectrum for each bunch within the train and bunch-by-bunch vertical beam size. In the position spectrum coherent betatron dipole and head-tail motion is detectable for each individual bunch within the train. 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 of the vertical enlargement of the first bunch(es) in 30 bunch-long trains. We also report that the addition of a precursor bunch following the train of bunches and before the start of the next train can counteract the vertical enlargement of the first bunch(es) in the train. Results from these observations will be presented. 		 
 
TUPWA063 Dependence of Vertical Beam Dynamics Influenced by Electron Clouds at CesrTA on Variations in Bunch Spacing and Vertical Chromaticity electron, positron, synchrotron, emittance 1847
 
  • R. Holtzapple, R.F. Campbell, E.L. Holtzapple
    CalPoly, San Luis Obispo, California, USA
  • M.G. Billing, K.R. Butler, G. Dugan, M.J. Forster, B.K. Heltsley, G. Ramirez, N.T. Rider, J.P. Shanks, K.G. Sonnad
    CLASSE, Ithaca, New York, USA
  • J.W. Flanagan
    KEK, Ibaraki, Japan
  
  Funding: Work supported by DOE Award DE-FC02-08ER41538, NSF Award PHY-0734867, PHY-1068662 and the Lepton Collider R&D Coop. Agreement: NSF Award PHY-1002467
Experiments have been performed on the Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) to probe the interaction of the electron cloud with a 2-Gev stored positron beam. The purpose of these experiments was to characterize the beam–electron cloud interactions by varying the vertical chromaticity and bunch spacing. These experiments were performed on a 30-bunch positron train, at a fixed current of 0.75mA/bunch, where the bunch spacing was varied between 4 and 28ns at three different vertical chromaticity settings. The vertical beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using the x-ray beam size monitor (xBSM) that is used to measure the bunch-by-bunch, turn-by-turn vertical beam size of the bunch trains. In this paper, we report the results from these experiments and discuss the effects of the electron cloud on the CesrTA beam dynamics. 		 
 
WEPWO071 Quench and High Field Q-SLOP Studies using a Single Cell Cavity with Artificial Pits cavity, SRF, niobium, factory 2465
 
  • Y. Xie, G.H. Hoffstaetter, M. Liepe
    CLASSE, Ithaca, New York, USA
  
  Surface defects such as pits have been identified as some of the main sources of limitations of srf cavity performance. A single cell cavity was made with 30 artificial pits in the high magnetic field region to gain new insight in how pits limit the cavity performance. The test of the pit cavity showed clear evidence that the edges of two of the largest radius pits transitioned into the normal conducting state at field just below the quench field of the cavity, and that the quench was indeed induced by these two pits. Insights about quench and non-linear rf resistances will be presented.  
 
WEPEA010 Modeling Longitudinal Bunched Beam Dynamics in Hadron Synchrotrons using Scaled Fourier-Hermite Expansions synchrotron, simulation, hadron, controls 2513
 
  • K. Gross, D.E.M. Lens
    TU Darmstadt, RTR, Darmstadt, Germany
  
  To devise control strategies and to analyze the stability of systems with feedback, a set of few ODEs describing the underlying dynamics is required. Numerical Fourier-Hermite solutions of the Vlasov equation have been studied for over fifty years. The idea to expand the distribution function in Fourier series in space and Hermite functions in velocity is transferred to the dynamics of bunched beams in hadron synchrotrons in this contribution. The Hermite basis is a natural choice for plasmas with Maxwellian velocity profile as well as for particle beams with Gaussian momentum spread. The Fourier basis used for spatially nearly uniform plasmas has to be adapted to bunched beams where the beam profile is not uniform in phase. This is achieved analogously to the deduction of the three term recursion relations to construct orthogonal polynomials, but applied to Fourier series with the weight function taken from the Hamiltonian. The resulting system of ODEs for the expansion coefficients of desired order - dependent on the number of functions retained - is checked against macro particle tracking simulations.  
 
WEPEA065 Beam Tests and Plans for the CERN PS Booster Wideband RF System Prototype cavity, controls, LLRF, booster 2660
 
  • M.M. Paoluzzi, M. E. Angoletta, A. Findlay, M. Haase, M. Jaussi
    CERN, Geneva, Switzerland
  
  In the framework of the LHC Injectors Upgrade project (LIU) and in view of a complete replacement of the existing CERN PS Booster (PSB) RF systems, a prototype cavity has been installed beginning of 2012 in the machine. This modular, wideband (0.5 / 4 MHz), Finemet® loaded system uses solid-state power stages and includes fast RF feedback for beam loading compensation. In depth studies have been performed during 2012 to evaluate the system interaction with the new low-level digital electronics, its ability to accelerate the beam and cope with high beam intensity. The encouraging results suggest that this innovative approach can indeed be used to replace all the existing PSB RF systems but additional testing with a full scale prototype is required. This paper reports about the project status, the achieved results, the encountered difficulties and the foreseen prototype completion in preparation during 2013.  
 
WEPEA069 Review of the Drive Beam Stabilization in the CLIC Test Facility CTF3 linac, klystron, controls, low-level-rf 2666
 
  • A. Dubrovskiy, L. Malina, P.K. Skowroński, F. Tecker
    CERN, Geneva, Switzerland
  • T. Persson
    Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden
  
  CTF3 is a Test Facility focusing on beam-based studies of the key concepts of the Compact Linear Collider CLIC. Over the past several years many aspects the CLIC two-beam acceleration scheme were studied in CTF3, including the crucial issue of drive beam stability. The main sources of drifts and instabilities have been identified and mitigated, helping to improve the machine performance and showing significant progress towards the experimental demonstration of the very stringent requirements on current, energy and phase stability needed in CLIC. In this paper, the more effective techniques and feed-backs are summarized. The latest measurements on beam stability are reported and their relevance to CLIC is discussed.  
 
WEPFI005 Simulations and RF Measurements of the Fundamental and Higher Order Modes of the ThomX 500 MHz Cavity cavity, HOM, impedance, controls 2711
 
  • M. El Khaldi, I.V. Drebot, P. Lepercq, R. Marie, B. Mercier, T. Roulet, A. Variola, F. Wicek
    LAL, Orsay, France
  • H.D. Dias, M.D. Diop, M.E. El Ajjouri, R. Lopes, A. Loulergue, P. Marchand, F. Ribeiro, R. Sreedharan
    SOLEIL, Gif-sur-Yvette, France
  
  The RF system of the ThomX* storage ring consists in a 500 MHz single cell copper cavity of the ELETTRA type, powered with a 50 kW CW solid state amplifier, and the associated Low Level RF feedback and control loops. The low operating energy of 50 – 70 MeV makes the impedances of the cavity higher order modes (HOMs) particularly critical for the beam stability. Their parasitic effects on the beam can be cured by HOM frequency shifting techniques, based on a fine temperature tuning and a dedicated plunger. A typical cavity temperature stability of ± 0.05°C within a range from 35 up to 80 °C can be achieved by a precise control of its water cooling temperature. On the other hand, the tuning of the cavity fundamental mode is achieved by changing its axial length by means of a mechanical tuner. In order to insure a fine control of the HOM frequencies, a good knowledge of their characteristics is mandatory. The main parameters of the fundamental and of the HOMs up to 4 GHz have been calculated using the HFSS and CST MWS codes. Preliminary measurements results have been obtained and show a good agreement with the simulations.
* A.Variola, “The ThomX Project”, Proceedings of IPAC2011, San Sebastián, Spain 		 
 
WEPFI006 Broad and Narrow Band Feedback Systems at ELSA cavity, kicker, HOM, damping 2714
 
  • M. Schedler, F. Frommberger, P. Hänisch, W. Hillert, C. Reinsch
    ELSA, Bonn, Germany
  
  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 6 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. In addition, a narrow band cavity based feedback system for damping the most harmful longitudinal multi bunch mode caused by a HOM of the accelerating cavities is under construction.  
 
WEPFI007 Amplitude, Phase and Temperature Stabilization of the ELSA RF System cavity, LLRF, controls, HOM 2717
 
  • D. Sauerland, W. Hillert, A. Roth, M. Schedler
    ELSA, Bonn, Germany
  • D. Teytelman
    Dimtel, San Jose, USA
  
  In the stretcher ring of the accelerator facility ELSA electrons are accelerated to a maximum energy of 3.2 GeV applying a fast energy ramp of up to 6 GeV/s. In order to be able to offer higher external beam currents one has to increase the current of the internal beam in ELSA accordingly. The beam current is limited due to excitation of multi bunch instabilities which are mainly caused by higher order modes of the two PETRA cavities used for particle acceleration in the stretcher ring. To control the resonance frequency of these modes, a variable bypass of the cavities' cooling system has been installed which allows a stabilization of their temperature. With this modification, it is possible to vary the temperature of the cavities between 26 °C and 65 °C and thus to shift the higher order modes by hundreds of kHz in frequency. Additionally, first operational studies with a prototype of a FPGA based LLRF system (Dimtel) have been performed which in future will be used to stabilize the amplitude and phase of the accelerating RF fields of the cavities.  
 
WEPFI028 RF System of the CSNS Synchrotron cavity, controls, LLRF, synchrotron 2765
 
  • H. Sun, W.L. Huang, X. Li, W. Long, H. Shi, C.L. Zhang, F.C. Zhao
    IHEP, Beijing, People's Republic of China
  
  The accelerator of China Spallation Neutron Source (CSNS) consists of a H− linac and a rapid cycling synchrotron (RCS). The protons injected into the RCS will be accelerated from 81MeV to 1.6GeV by the Ring RF system providing a maximum accelerating voltage of 165kV. The RF frequency sweeps from 1.02 MHz to 2.44 MHz. with a repetition rate of 25Hz. The ferrite-loaded RF cavities will be used in the ring RF system. Each cavity has own RF power tube amplifier, bias current supply and full digital LLRF control loops. The R&D of ring rf system have been completed, it compose of the prototypes of a full size ferrite loaded RF cavity, a high power tetrode amplifier, a switching type bias supply of 3000A and a full digital embedded controller of LLRF. CSNS ring RF system design and the results of the R&D will be described in this paper.  
 
WEPME001 SOLEIL Beam Stability Status coupling, emittance, undulator, electron 2917
 
  • N. Hubert, L. Cassinari, J.-C. Denard, M. Labat, J.-F. Lamarre, A. Nadji, L.S. Nadolski, D. Pédeau, M.-A. Tordeux
    SOLEIL, Gif-sur-Yvette, France
  
  This paper reports recent work for improving SOLEIL electron beam stability. X-BPMs from four bending magnet beamline frontends have been inserted in the global orbit feedback loops during user operation. The corresponding source point stabilities have improved and results are reported. Some of the new beamlines request more stringent stability than the existing ones. Their requirements are not only tighter for beam orbit but also for beam size and divergence stability. For these reasons, SOLEIL has decided to define beam quality criteria for each sensitive beamline. Then it can predict ahead of commissioning how well the beamline will likely perform. A feedback on the vertical emittance, measured by a pinhole camera, has been introduced in order to reduce beam size and divergence variations due to magnetic configuration changes of a few insertion devices.  
 
WEPME002 Fast Orbit Feedback at BESSY-II: Performance and Operational Experiences controls, booster, status, injection 2920
 
  • R. Müller, T. Birke, M. Diehn, D.B. Engel, B. Franksen, R. Görgen, P. Kuske, R. Lange, I. Müller, A. Schälicke, G. Schindhelm
    HZB, Berlin, Germany
  
  At the 3rd generation light source BESSY II the first phase of a fast orbit feedback system(*) has been completed and put into operation in 2012. In this first phase the aim was to achieve noise suppression in the 1Hz to several 10Hz range, mostly avoiding expensive upgrades to existing hardware, such as beam position monitors and the CAN based setpoint transmission to the power supplies. Only the power supplies were replaced with newer, faster versions. This paper describes the capability of the phase-I FOFB with respect to beam motion transient suppression, low frequency damping and high frequency noise generation as well as aspects of operational integration and stability.
* Müller, R. et. al.: Installing a Fast Orbit Feedback at BESSY.
IPAC 10, Kyoto, Japan, 23 - 28 May, 2010., p. 2749-2751
 		 
poster icon Poster WEPME002 [2.720 MB]  
 
WEPME003 Determination of Optics Transfer between the Kicker and BPMs for Transverse Feedback System kicker, betatron, optics, synchrotron 2923
 
  • M. Alhumaidi, A.M. Zoubir
    TU Darmstadt, Darmstadt, Germany
  • J. Grieser
    TU Darmstadt, RTR, Darmstadt, Germany
  
  The knowledge of the transfer optics between the positions of the Kicker and the BPMs is required for the calculation of the correction signal in transverse feedback systems. Therefore, using nominal values of the transfer optics with uncertainties leads to feedback quality degradation, and thus beam disturbances. In this work, we propose a method for measuring the phase advances and amplitude scaling between the positions of the kicker and the BPMs. Directly after applying a kick on the beam by means of the kicker, we record the BPM signals. Consequently, we use the Second-Order Blind Identification (SOBI) algorithm to decompose the noised recorded signals into independent sources mixture. Finally, we determine the required optics parameters by identifying and analyzing the betatron oscillation sourced from the kick based on its mixing and temporal patterns. Results for the heavy ions synchrotron SIS 18 at the GSI are shown.  
 
WEPME004 A Digital Beam-Phase Control System for a Heavy-Ion Synchrotron with a Double-Harmonic Cavity System controls, cavity, synchrotron, dipole 2926
 
  • J. Grieser, D.E.M. Lens
    TU Darmstadt, RTR, Darmstadt, Germany
  • U. Hartel
    TEMF, TU Darmstadt, Darmstadt, Germany
  • H. Klingbeil, U. Laier, K.-P. Ningel, S. Schäfer, B. Zipfel
    GSI, Darmstadt, Germany
  
  Funding: Funded by GSI Helmholtzzentrum für Schwerionenforschung GmbH
For the new Facility for Antiproton and Ion Research (FAIR) at GSI Helmholtzzentrum für Schwerionenforschung GmbH, the heavy-ion synchrotron SIS18 will be operated with a double-harmonic cavity system*. The second cavity, running at twice the fundamental RF frequency, is used to lengthen the bucket which introduces nonlinearities to the control system. To damp longitudinal rigid dipole oscillations a digital feedback system consisting of a filter and an integrator is used. For the existing single-harmonic setup an FIR-filter is implemented which realizes a multiple bandpass filter with the first passband close to the synchrotron frequency. Both, the feedback gain and the passband frequency of the filter depend on the actual value of the synchrotron frequency**. It was shown by simulations and in an experiment that this setup can be transferred to a double-harmonic cavity system obtaining similar results for the region of stable feedback parameters, if the oscillation frequency of the bunch barycenter*** is considered instead of the synchrotron frequency of a linearized bucket. In this contribution the results of the simulation and the experiment are presented and compared.
*Klingbeil et al.: Phys. Rev. Special Topics - Accelerators and Beams 14, 102802, 2011
**Klingbeil et al.: IEEE Trans. on Nucl. Science, Vol. 54, No. 6, 2007
***Grieser et al.: Proc. 3rd IPAC, 2012 		 
 
WEPME006 Optical Synchronization and Electron Bunch Diagnostic at ELBE laser, electron, pick-up, wakefield 2932
 
  • M. Kuntzsch, M. Gensch, U. Lehnert, F. Röser, R. Schurig
    HZDR, Dresden, Germany
  • M. Bousonville, M.K. Czwalinna, H. Schlarb, S. Schulz, S. Vilcins
    DESY, Hamburg, Germany
  
  The continuous wave electron accelerator ELBE is upgraded to generate short and highly charged electron bunches (~200fs duration, up to 1 nC) . In the last years a prototype of an optical synchronization system using a mode locked fiber laser has been build up at ELBE which is now in commissioning phase. The stabilized pulse train can be used for new methods of electron bunch diagnostics like bunch arrival time measurements with the potential of femtosecond resolution. At ELBE a bunch arrival time monitor (BAM) has been designed and tested at the accelerator. The contribution will show the design of the BAM and first measurement results at the ELBE accelerator.  
 
WEPME010 Patient-specific Intensity-modulation of a Slowly Extracted Beam at the HIT Synchrotron ion, controls, synchrotron, extraction 2944
 
  • C. Schömers, E. Feldmeier, Th. Haberer, J. Naumann, R.E. Panse, A. Peters
    HIT, Heidelberg, Germany
  
  Since 2009 more than 1100 tumour patients have been treated at the Heidelberg Ion Therapy-Centre (HIT). The HIT synchrotron produces a library of energy, focus and intensity-variable pencil beams used to deliver dose distributions of utmost conformity to irregularly shaped target volumes. The required number of particles for each volume element of the tumour, which can vary by more than two magnitudes, is applied using the rasterscan technology. The irradiation-time and thus the patient throughput are highly sensitive to the achieved spill-structure driven by RF-Knockout extraction. Presently unfavourable fluctuations of the extracted intensity due to inhomogeneous phase space distribution of the beam are present. Recently a feedback-loop coupling the dose-defining ionisation chamber in front of the patient with the RF-Exciter was implemented allowing for the adaptation of the extracted intensity to the patient-specific treatment plan in real-time. The technical implementation and the impact on the clinical operation will be discussed.  
 
WEPME013 Development and Test of a Fully Automated PkQl Control Procedure at KEK STF cavity, controls, LLRF, klystron 2950
 
  • M. Omet, A. Kuramoto
    Sokendai, Ibaraki, Japan
  • H. Hayano, T. Matsumoto, S. Michizono
    KEK, Ibaraki, Japan
  
  In order to operate the cavities near their maximum gradients, cavity input (Pk) and cavity loaded Q (QL) should be controlled individually (PkQL control) at the International Linear Collider (ILC). A manual PkQL operation procedure was developed and performed at the linear electron accelerator at the Superconducting RF Test Facility (STF), in which the beam is accelerated up to 40 MeV by two superconducting 9-cell TESLA type L band cavities. The cavity gradients were set to 16 MV/m and 24 MV/m with QL values of 1106 and 3·106. A 6.2 mA beam with a pulse length of 154 us was used. The field stabilities in amplitude were 0.160% and 0.097% for the cavities and 0.016% for the vector sum. The stabilities without beam are 0.057% and 0.054% for the cavities and 0.009% for the vector sum. For stability improvement during beam transient an adaptive beam feedforward for beam loading compensation is under development. So far an amplitude field stability of 0.013% for the vector sum was achieved at cavity gradients of 15 MV/m and 25 MV/m (no PkQL control) during a 6.8 mA beam with a pulse length of 123 us. Furthermore a fully automated PkQL control procedure is currently developed and tested.  
poster icon Poster WEPME013 [0.647 MB]  
 
WEPME016 Recent Progress of a Laser-based Alignment System at the KEKB Injector Linac laser, alignment, linac, controls 2959
 
  • T. Suwada, M. Satoh
    KEK, Ibaraki, Japan
  • K. Minoshima, S. Telada
    AIST, Tsukuba, Japan
  
  A new laser-based alignment system is under development in order to precisely align accelerator components with a precision level of ±0.1 mm along an ideal straight line at the KEKB injector linac. The high-precision alignment system is strongly required for the Super B-factory at KEK. The laser-based alignment system comprises a He-Ne laser source and optical components for delivering the laser beam, and silicon photodetectors. The laser-based alignment system aligns a misalignment of a girder unit for accelerating structures while accelerator components on the girder unit are aligned with another laser tracker system with a similar precision level. A new PC-based feedback system for the laser pointing stability has been introduced in order to stabilize the transverse laser positions at the photodetector. The experimental results show that although the laser pointing stability is easily disturbed by environmental factors without the feedback system, it has been successfully applied to control the laser pointing stability within a few ten-micron-meter. In this report, the experimental investigations in the new feedback system are reported.  
 
WEPME019 Development of Beam Position Feedback Control System in KU-FEL FEL, gun, controls, electron 2968
 
  • H. Ohgaki, Y.W. Choi, H. Imon, T. Kii, R. Kinjo, T. Konstantin, K. Masuda, H. Negm, K. Okumura, M. Omer, S. Shibata, K. Shimahashi, K. Yoshida, H. Zen
    Kyoto University, Institute for Advanced Energy, Kyoto, Japan
  
  The stability of electron beam parameters such as position, energy etc. is very crucial for stable FEL operation. In Kyoto University MIR-FEL facility (KU-FEL), fluctuation of beam position and energy is caused by external fluctuations, such as the fluctuation in the cathode temperature of the thermionic RF-gun due to the back-streaming electrons, fluctuation of RF phase and amplitude, fluctuations of room and water temperatures, electric noises and so on. To monitor electron beam movement, we have already developed BPM system consisting of a 4-button electrode type BPM, a heterodyne detector, and CAMAC ADC in KU-FEL. By using this BPM system we have observed some correlations between external fluctuations and the beam position movements. In this conference, we will present the developed BPM system as well as the beam feedback system for stable KU-FEL operation.  
 
WEPME022 Overview of the CSNS/RCS LLRF Control System cavity, controls, LLRF, beam-loading 2977
 
  • X. Li, W. Long, H. Sun, C.L. Zhang, F.C. Zhao
    IHEP, Beijing, People's Republic of China
  
  The CSNS/RCS RF system consists of 8 ferrite-loaded RF cavities (h=2), each with individual digital LLRF control electronics. The injection and extraction energy of the beam are 80MeV and 1.6GeV respectively with a repetition rate of 25Hz. The RF system is designed to provide the maximum RF voltage of 165kV. The RF frequency range is from 1.02MHz at injection to 2.44MHz at extraction. The CSNS/RCS LLRF control system is based on FPGA, and composed of 7 control loops to achieve required acceleration voltage amplitude and phase regulation. A number of prototype and the first formal system have been completed and tested. In this paper we present an overview of the LLRF control system, and some operational results.  
 
WEPME033 Status of SSRF Fast Orbit Feedback System EPICS, power-supply, controls, synchrotron 2995
 
  • C.X. Yin, B.C. Jiang, L.Y. Zhao
    SINAP, Shanghai, People's Republic of China
  
  As a 3rd generation light source, Shanghai Synchrotron Radiation Facility (SSRF) is pushing the requirement of beam stability to sub-micron in the range of DC to 100Hz. A fast orbit feedback system was designed and implemented to satisfy this requirement. In this paper, the layout of SSRF fast orbit feedback system, the structure of its electronics system and its hardware and software subsystems are described. The current status of SSRF fast orbit feedback system is presented.  
 
WEPME037 Fast Orbit Feedback at Taiwan Photon Source brilliance, controls, EPICS, storage-ring 3007
 
  • A. Bardorfer, P. Leban
    I-Tech, Solkan, Slovenia
  • P.C. Chiu, K.T. Hsu, C.H. Kuo
    NSRRC, Hsinchu, Taiwan
  
  Low latency, distributed, Fast Orbit Feedback (FOFB) application, based on singular value decomposition, entirely implemented in FPGA, has been developed for the Taiwan Photos Source (TPS). The FOFB utilizes the latest Libera Brilliance+ units for measuring beam position and the Gigabit Data eXchange (GDX) modules, which take care of global orbit distribution via 6.5 Gbit/s fiber optic or passive Cu links, and provide a large orbit data history buffer. The magnet correction in a matrix form of M = V . PI( S-1 . UT . ( Golden-Orbit ) ) is calculated entirely in FPGA, using a massively parallel approach and sent to the magnet power supplies via 2.5 Gbit/s link. The entire FOFB calculation is distributed over 48 GDX modules and the system allows for synchronous (on/off/pause) FOFB control via external input signal. The latencies of 60 ns per BPM for orbit distribution, 1.5 us for FOFB calculation and 1.5 us for magnet data transmission have been measured at TPS test installation in November 2012. The expected total communication and FOFB calculation latency in the TPS final configuration (168 BPMs) is expected to stay within 15-20 us range.  
 
WEPME038 Slow Orbit Feedback and Beam Stability at ALBA photon, injection, wiggler, electron 3010
 
  • J. Marcos, M. Muñoz
    CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
  
  ALBA is a 3GeV 3rd generation synchrotron radiation source built nearby Barcelona providing service to users since May 2012. During all this period, a Slow Orbit Feedback system (SOFB) has been running during users’ operation in order to deliver a stable photon beam to the Beamlines. The system employs 88 out of the 104 Beam Position Monitors (BPMs) available at ALBA and 88 horizontal and vertical correctors. In addition, since the middle of the year (July 2012), the reading of the X-Ray BPM (XBPM) for one of the Front Ends, with a Bending Magnet as a source, has also been included in the correction loop. In this paper we summarize the performance of the SOFB system. Besides, we also present data corresponding to the evolution along the year of the XBPM readings for several Front Ends that have a planar Insertion Device (ID) as a source. The analyzed XBPMs are not included in the orbit correction loop, and consequently they supply information regarding the long term stability of ALBA Storage Ring.  
 
WEPME040 Investigation to Reduce Power Overhead Required in Superconducting RF Cavity Field Control klystron, cavity, controls, cathode 3013
 
  • R. Zeng, S. Molloy, A. Sunesson
    ESS, Lund, Sweden
  • A.J. Johansson
    Lund University, Lund, Sweden
  
  A power overhead of more than 25% is usually required in RF field control of klystron drived superconducting cavity, since it is much easier to implement feild control in a linear region of klystron where it is far below saturation. It however results in a reduced efficiency and more power consumption. Within ESS project it places very high demands on energy efficiency, which leads to stringent requirements on power overhead required in RF field control. Investigation on power overhead reduction in RF field control has been carried out at ESS and related simulation has been done. In this paper we will look at how close we can implement field control to the klystron saturation and discuss if it is possible to make RF field control the RF field with 10% overhead.  
 
WEPME042 Modelling and Studies for a Wideband Feedback System for Mitigation of Transverse Single Bunch Instabilities kicker, pick-up, injection, electron 3019
 
  • K.S.B. Li, W. Höfle, G. Rumolo
    CERN, Geneva, Switzerland
  • J.M. Cesaratto, J.E. Dusatko, J.D. Fox, M.T.F. Pivi, K.M. Pollock, C.H. Rivetta, O. Turgut
    SLAC, Menlo Park, California, USA
  
  As part of the LHC injector upgrade a wideband feedback system is under study for mitigation of coherent single bunch instabilities. This type of system may provide a generic way of shifting the instability threshold to regions that are currently inaccessible, thus, boosting the brightness of future beams. To study the effectiveness of such systems, a numerical model has been developed that constitutes a realistic feedback system including real transfer functions for pickup and kicker, realistic N-tap FIR and IIR filters as well as noise and saturation effects. Simulations of SPS cases have been performed with HeadTail to evaluate the feedback effectiveness in the presence of electron clouds and TMCI. Some results are presented addressing bandwidth limitations, noise issues and amplifier power requirements.  
 
WEPME043 Performance of the LHC Transverse Damper with Bunch Trains damping, injection, kicker, pick-up 3022
 
  • W. Höfle, F. Dubouchet, G. Kotzian, D. Valuch
    CERN, Geneva, Switzerland
  
  In 2012 the LHC has operated for Physics with bunch trains at 50 ns spacing. Tests have been performed with the nominal design bunch spacing of 25 ns. The transverse damper has been an essential element to provide beam stability for the multi-bunch beam with up to 1380 bunches used at 50 ns spacing. We report on the experience gained with 50 ns spacing and the improvements in the signal processing tested for the future 25 ns operation. The increase in bandwidth required for 25 ns spacing constituted a particular challenge. The response of the system was carefully measured and the results used to digitally pre-distort the drive signal to compensate for a drop in gain of the power system for higher frequencies. The bunch-by-bunch data collected from the feedback signal path provided valuable information during the 2012 Physics run that can be further explored for beam diagnostics purposes and instability analysis in the future. Performance estimates are given for the 7 TeV run planned for 2015, at 25 ns bunch spacing.  
 
WEPME047 Identification of Sources of Orbital Distortions in Corrector Space quadrupole, alignment, controls, damping 3034
 
  • M. Böge, M. Aiba, A. Saá Hernández, A. Streun
    PSI, Villigen PSI, Switzerland
  
  Since modern ring and linear accelerator based light sources feature fast orbit feedback (FOFB) systems which transform orbital oscillations in beam position monitor (BPM) space into corrector (C) space over a wide frequency range, most perturbations can be directly analyzed utilizing the C pattern. In C space the localization of sources of distortions is facilitated since the large (per unit phase) number of BPMs and Cs involved provides a good spatial resolution. Applications of this technique include the beam-assisted girder alignment where changes in the C pattern are interactively analyzed while girder positions are remotely altered or the beam-based alignment of quadrupole/BPM pairs where the variation of C values as the result of quadrupole variations are observed. In both cases large oscillations in BPM space are completely surpressed by the FOFB leading to well controlled and stable conditions during the measurement.  
 
WEPME053 Latest Performance Results from the FONT 5 Intra Train Beam Position Feedback System at ATF kicker, extraction, cavity, linear-collider 3049
 
  • M.R. Davis, D.R. Bett, N. Blaskovic Kraljevic, P. Burrows, G.B. Christian, Y.I. Kim, C. Perry
    JAI, Oxford, United Kingdom
  • R. Apsimon, B. Constance, A. Gerbershagen
    CERN, Geneva, Switzerland
  
  A prototype ultra-fast beam-based feedback system for deployment in single-pass beamlines, such as a future lepton collider (ILC or CLIC) or a free-electron laser, has been fabricated and is being tested in the extraction and final focus lines of the Accelerator Test Facility (ATF) at KEK. FONT5 is an intra-train feedback system for stabilising the beam orbit via different methods: a position and angle feedback correction in the extraction line or a vertical feedforward correction applied at the interaction point (IP) . Two systems comprise three stripline beam position monitors (BPMs) and two stripline kickers in the extraction line, two cavity BPMs and a stripline kicker at the IP, a custom FPGA-based digital processing board, custom kicker-drive amplifiers and low-latency analogue front-end BPM processors. Latest results from the experiment are presented. These include beam position correction in the extraction line, as well as preliminary results of beam correction at the IP.  
 
WEPME055 Investigation of Source Point Instabilities in Dipole Magnet Based Beamlines dipole, synchrotron, optics, radiation 3055
 
  • M. Apollonio, R. Bartolini
    Diamond, Oxfordshire, United Kingdom
  • R. Bartolini
    JAI, Oxford, United Kingdom
  
  At Diamond the source point in the second dipole of the Double Bend Achromats can vary due the lack of adjacent BPMs constraining angle and position of the electron beam at the dipole. We have implemented a code based on our AT model to predict the effects of a corrector strength change and compared our predictions to data both from a beamline and from our pinhole cameras. We discuss the possibility of interfacing the code to a ray tracing routine in order to infer beam spot changes in the downstream beamline and suggest a procedure to restore the original source point.  
 
WEPME056 Application of Z-transform to Noise Response Modeling of a Bunch-by-bunch Feedback System storage-ring, lattice, pick-up, monitoring 3058
 
  • C. Yao, N.P. Di Monte, A.J. Scaminaci, H. Shang
    ANL, Argonne, USA
  
  Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-ACO2-O6CH11357.
The APS storage ring has an electron beam energy of 7 GeV and a single current of up to 16 mA. Transverse beam instability is corrected by a combination of chromatic correction and bunch-by-bunch feedback system. Noises produced in the pickup circuits is processed and transferred to the beam the same as a beam signal, which contributes to beam motion when the loops are closed. By analyzing the input data stream of the feedback system, one can passively obtain useful information, such as the tunes, loop stability, noise spectrum, etc. This approach has been reported by J. Klute and D. Teytelman. We implemented a passive and continuous tune monitoring process at the APS storage ring. In order to understand the underlying principle, we applied z-transform analysis to the noise-response model of a bunch-by-bunch feedback system. Our analysis shows a clear relationship between the spectrum of the noise response and the open-loop response of the beam. The noise-response model can also be applied to other areas, such as stability and noise analysis of a bunch-by-bunch feedback system. This report presents our analysis and some experimental data. 		 
 
WEPME059 A 4 GS/sec Instability Feedback Processing System for Intra-bunch Instabilities controls, pick-up, kicker, injection 3067
 
  • J.E. Dusatko, J.M. Cesaratto, J.D. Fox, J.J. Olsen, K.M. Pollock, C.H. Rivetta, O. Turgut
    SLAC, Menlo Park, California, USA
  • W. Höfle
    CERN, Geneva, Switzerland
  
  Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research program ( LARP)
We present the architecture and implementation overview of a proof-of-principle digital signal processing system developed to study control of Electron-Cloud and Transverse Mode Coupling Instabilities (TMCI) in the CERN SPS. This system is motivated by intensity increases planned as part of the High Luminosity LHC upgrade. It is based on a reconfigurable processing architecture which samples intra-bunch motion and applies correction signals at a 4GSa/s rate, allowing multiple samples across a single 2ns SPS bunch. This initial demonstration system is a rapidly developed prototype consisting of both commercial and custom-designed hardware that implements feedback control on a single bunch. It contains a high speed ADC and DAC, capable of sampling at up to 4GSa/s, with a 16-tap FIR control filter for each bunch sample slice. Other system features include a timing subsystem to synchronize the sampling to the injection and the bunch 1 markers, the capability of generating arbitrary time domain signals to drive the bunch and diagnostic functions including a snapshot memory for ADC data. This paper describes the design, construction and operational experience of this system. 		 
 
WEPME060 First Results and Analysis of the Performance of a 4 GS/s Intra-bunch Vertical Feedback System at the SPS controls, kicker, injection, damping 3070
 
  • J.M. Cesaratto, J.E. Dusatko, J.D. Fox, J.J. Olsen, K.M. Pollock, C.H. Rivetta, O. Turgut
    SLAC, Menlo Park, California, USA
  • H. Bartosik, W. Höfle, G. Kotzian, U. Wehrle
    CERN, Geneva, Switzerland
  
  Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research program ( LARP)
We present experimental measurements taken from SPS machine development studies with an intra-bunch feedback channel. These studies use a digital signal processing system to implement general-purpose control algorithms on multiple samples across a single SPS bunch ( for ease of synchronization with the SPS RF frequency a sampling frequency of 3.2 GS/sec. is implemented). These initial studies concentrate on single-bunch motion, and study the vertical betatron motion as the feedback control is varied. The studies are focused on validating simulation models of the beam dynamics with feedback. Time and frequency domain results include excitation and damping of intra-bunch motion with positive and negative feedback. We present an overview of the challenges of intra-bunch feedback, and highlight methods to time-align the pickup and kicker signals within the closed-loop feedback channel. 		 
 
WEPME061 A Wideband Slotted Kicker Design for SPS Transverse Intra-bunch Feedback kicker, impedance, coupling, simulation 3073
 
  • J.M. Cesaratto, J.D. Fox, C.H. Rivetta
    SLAC, Menlo Park, California, USA
  • D. Alesini, A. Drago, A. Gallo, F. Marcellini, M. Zobov
    INFN/LNF, Frascati (Roma), Italy
  • S. De Santis
    LBNL, Berkeley, California, USA
  • W. Höfle
    CERN, Geneva, Switzerland
  
  Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP) and by the EU FP7 HiLumi LHC - Grant Agreement 284404.
Control and mitigation of transverse beam instabilities caused by electron cloud and TMCI will be essential for the SPS to meet the beam intensity demands for the HL-LHC upgrade. A wideband intra-bunch feedback method is in development, based on a 4 GS/s data acquisition and processing, and with a back end frequency structure extending to 1 GHz. A slotted type kicker, similar to those used for stochastic cooling, has been considered as the terminal element of the feedback chain. It offers the most promising deflecting structure characteristics to meet the system requirements in terms of bandwidth, shunt impedance, and beam coupling impedance. Different types of slotted structures have been explored and simulated, including a ridged waveguide and coaxial type waveguide. In this paper we present our findings and the conceptual design of a vertical SPS wideband kicker consistent with the stay clear, vacuum, frequency band coverage, and peak shunt impedance requirements. 		 
 
THPEA031 REGAE LLRF Control System Overview controls, electron, LLRF, laser 3210
 
  • I. Rutkowski, L. Butkowski
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  • M. Hoffmann, H. Schlarb, Ch. Schmidt
    DESY, Hamburg, Germany
  
  The linear accelerator REGAE (Relativistic Electron Gun for Atomic Exploration) at DESY delivers electron bunches with a few femtosecond duration for time-resolved investigation of material structures in pump-probe configuration. To achieve sub-10fs resolution, the Low Level RF controls for the normal conducting S-band cavities must provide field stability of .005% in amplitude and of .005deg in phase. To achieve these demands, the recently developed LLRF control modules based on the Micro-Telecommunications Computing Architecture (MTCA.4) platform are used. For precise field detection and control a rear transition module (DRTM-DWC8VM1) housing 8 down-converters and 1 vector-modulator has been developed. The down-converted signals are transmitted to low-noise ADCs on an advanced mezzanine card (SIS8300L) with two high speed DACs driving the vector-modulator. The on board FPGA device runs the advanced control algorithms with minimum latency. Shot-to-shot learning feed forward and ultra-fast analog and digital feedbacks are applied. In this paper, the first results of the new RTM-AMC module pairs are presented together with the achievements and limitations on the RF field stability.  
 
THPEA046 Machine Protection at the LHC - Experience of Three Years Running and Outlook for Operation at Nominal Energy injection, synchrotron, extraction, optics 3246
 
  • D. Wollmann, R. Schmidt, J. Wenninger, M. Zerlauth
    CERN, Geneva, Switzerland
  
  With above 22fb-1 integrated luminosity delivered to the experiments ATLAS and CMS the LHC surpassed the results of 2011 by more than a factor 5. This was achieved at 4TeV, with intensities of ~2e14p per beam. The uncontrolled loss of only a small fraction of the stored beam is sufficient to damage parts of the sc. magnet system, accelerator equipment or the particle physics experiments. To protect against this a correct functioning of the complex LHC machine protection (MP) systems through the operational cycle is essential. Operating with up to 140MJ stored beam energy was only possible due to the experience and confidence gained in the two previous running periods, where the intensity was slowly increased. In this paper the 2012 performance of the MP systems is discussed. The strategy applied for a fast, but safe, intensity ramp up and the monitoring of the MP systems during stable running periods are presented. Weaknesses in the reliability of the MP systems, set-up procedures and setting adjustments for machine development periods, discovered in 2012, are critically reviewed and improvements for the LHC operation after the up-coming long shut-down of the LHC are proposed.  
 
THPEA060 LLRF System for LCLS-II at SLAC LLRF, controls, klystron, linac 3276
 
  • Z. Geng, B. Hong, K.H. Kim, R.S. Larsen, D. Van Winkle, C. Xu
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by US Department of Energy Contract DE AC03 76SF00515
After LCLS-I successfully delivering the full operation for users, SLAC has been approved to build the second Linac Coherent Light Source, LCLS-II, which makes use of another third of the 2-mile long Linac from Sector 10 to Sector20. The LLRF System will use mTCA (Micro Telecommunication Computing Architecture) to replace the VME system for LCLS-II injector and some key stations along the LINAC. The faster data acquisition and more powerful FPGA and CPU in the mTCA system enable the LLRF system to extend its control ability to a 2.5 μsec beam pulse rate of 360Hz. The new LLRF system is more compact and has the capability of low latency intra-pulse feedback to reduce fast phase and amplitude jitter during a single pulse. The prototype of the mTCA based LLRF control system has been operating at RF station 28-2 in LCLS-I. Detailed design structure and the prototype experimental results will be presented that demonstrate the system meets the exacting phase and amplitude stability requirements for LCLS-II. 		 
 
THPFI007 Increasing the Stability of the Electron Beam of the S-DALINAC linac, electron, acceleration, dipole 3303
 
  • F. Hug, T. Bahlo, C. Burandt, J. Conrad, L.E. Jürgensen, M. Kleinmann, M. Konrad, T. Kürzeder, N. Pietralla
    TU Darmstadt, Darmstadt, Germany
  • R. Eichhorn
    CLASSE, Ithaca, New York, USA
  
  Funding: Funded by DFG through SFB 634
The S-DALINAC is a superconducting recirculating electron accelerator with a final energy of 130 MeV. It operates in cw at 3 GHz. It accelerates beams of either unpolarized or polarized electrons and is used as a source for nuclear- and astrophysical experiments at the university of Darmstadt since 1987. We will report on two future upgrade plans for increasing the operation stability of the accelerator: A high energy scraper system for collimating the beam before it is delivered to the experiments and a rf feedback system to fix the rf phase of the beam leaving the injector linac by measurements on a rf monitor. 		 
 
THPFI078 Design and Experiment on Auto-alignment Control System of Taiwan Photon Source alignment, laser, controls, storage-ring 3475
 
  • M.H. Wu, J.-R. Chen, M.L. Chen, P.S.D. Chuang, H.C. Ho, K.H. Hsu, D.-G. Huang, W.Y. Lai, C.-S. Lin, C.J. Lin, H.C. Lin, H.M. Luo, S.Y. Perng, P.L. Sung, T.C. Tseng, H.S. Wang
    NSRRC, Hsinchu, Taiwan
  • J.-R. Chen
    National Tsing Hua University, Hsinchu, Taiwan
  
  TPS (Taiwan Photon Source) is a new 3-GeV synchrotron ring to be constructed at the NSRRC (National Synchrotron Radiation Research Center), Taiwan. There were hundreds of magnets that must be aligned on the absolute position to keep the electronic beam in the desire path while orbiting. Due to the problems of manpower, set up time, accuracy of adjustment, deformation of the floor, limited workspace and frequent earthquakes in Taiwan, an auto-alignment girder control system was designed to meet this requirement. The design and experiment of the auto-alignment system were tested successfully in the laboratory at NSRRC. The experiment of the auto-alignment control system would be implemented with half of the ring girders in the TPS. The detailed alignment design and status will be discussed in this paper.  
 
THPWA029 Transient Ionizing Radiation Effect of Bipolar Operational Amplifiers to Pulsed X-rays radiation, electron, controls, injection 3687
 
  • X.M. Jin
    Xiaoming Jin, People's Republic of China
  • X.Y. Bai, R.B. Li, D.S. Lin, Q. Ma, C. Qi, G.Z. Wang, S.C. Yang
    NINT, Xi'an, People's Republic of China
  
  Abstract – The pulsed ionizing radiation effect of monolithic operational amplifiers is investigated using a flash X-ray facility. The experimental results show that the pulsed ionizing radiation produces voltage surges in the devices and the output voltage recovers linearly after transient disturbance which includes a negative peak and a positive peak. The recovery time depends on the amplitude of the positive peak and the inherent slew rate of the devices. The degradation of transient disturbance amplitude and the recovery time versus ionizing dose rate of pulsed X-rays is researched. The relationship of circuit effects to physical mechanisms is investigated in detail. The photocurrent induced by transient ionizing radiation in the PN junctions in integrated circuits is responsible for the electrical degradation. Keywords – Transient ionizing Radiation effect, Transient disturbance, Photocurrent, integrated circuits  
 
THPWA035 Intervention Management from Operation to Shutdown radiation, controls, site, cryogenics 3705
 
  • C. Garino, B. Daudin, J. De Jonghe, A. Dorsival, F. B. Dos Santos Pedrosa, G. Dumont, K. Foraz, E.R.F. Reguero Fuentes
    CERN, Geneva, Switzerland
  
  The Intervention Management Planning and Coordination Tool (IMPACT) is now widely used in all the accelerator complex and beyond. This unique repository improves the availability of the intervention information for all facilities, and enhances its traceability. It supports a standardized approval workflow and direct link to the access system for improved control and productivity. IMPACT currently has 1418 active users who have defined 6880 intervention requests in 2012 so far. In 2013, the CERN Accelerator complex will enter a shutdown mode after a long period of operation. Careful preparation and scheduling of activities is paramount in order to keep the shutdown as short as possible, whilst guaranteeing safety. During execution, strict control of access will be enforced considering the radiation levels. This paper will summarize the main improvements to IMPACT in this context: work dose planning with respect to ALARA principles including integration with the operational dosimetry system and automatic generation of safety documents from intervention data.  
 
FRXCA01 Progress in Transverse Feedbacks and Related Diagnostics for Hadron Machines injection, kicker, hadron, damping 3990
 
  • W. Höfle
    CERN, Geneva, Switzerland
  
  Today Hadron Accelerators with high intensity and high brightness beams increasingly rely on transverse feedback systems for the control of instabilities and the preservation of the transverse emittance. With particular emphasis, but not limited, to the CERN Hadron Accelerator Chain the progress made in recent years and the performances achieved are reviewed. Hadron colliders such as the LHC represent a particular challenge as they ask for low noise electronic systems in these feedbacks for acceptable emittance growth. Achievements of the LHC transverse feedback system used for damping injection oscillations and to provide stability throughout the cycle are summarized. This includes its use for abort gap and injection cleaning as well as transverse blow-up for diagnostics purposes. Beyond systems already in operation, advances in technology and modern digital signal processing with increasingly higher digitization rates have made systems conceivable to cure intra-bunch motion. With its capabilities to both acquire beam oscillations and to actively excite motion, transverse feedback systems have a large variety of applications for beam diagnostics purposes.  
slides icon Slides FRXCA01 [4.985 MB]