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feedback

       
Paper Title Other Keywords Page
TUYMA03 Commissioning and Status of the Diamond Storage Ring injection, storage-ring, vacuum, closed-orbit 66
 
  • R. P. Walker
    Diamond, Oxfordshire
  Diamond is the UK's new 3'rd Generation Synchrotron Light Source. The construction phase has just concluded and the first operation with external users is about to begin. This presentation will concentrate on the second phase of commissioning of the storage ring at the full energy of 3GeV, which began in September 2006, with a full set of 7 Phase I Insertion Devices installed. The current status and future plans will also be described.  
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TUZH103 Electron Cloud Experiments, Simulation and Cure electron, simulation, quadrupole, dipole 89
 
  • H. Fukuma
    KEK, Ibaraki
  A large number of electrons called electron clouds have been observed both in positron and hadron accelerators. Possible sources of the electron clouds are photoelectrons generated by synchrotron radiation, electrons produced by beam hitting vacuum components, electrons multiplied by beam induced multipacting, electrons created by ionization of residual gasses and so on. The electron clouds produce various effects such as pressure rise, heat load on a cold chamber wall, beam induced multipacting, betatron tune shifts, coupled bunch instability and beam size blow-up which often limit the performance of the accelerators. Many experimental and theoretical studies on the electron clouds have been carried out and their results have contributed to the improvement of performance of existing accelerators and design of future accelerators. This talk reviews experiments, simulations and cures of the electron cloud effects in positron and hadron accelerators.  
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TUPMA014 State of the SLS Multi-bunch Feedback synchrotron, injection, kicker, storage-ring 118
 
  • M. Dehler, G. Marinkovic, P. Pollet, T. Schilcher
    PSI, Villigen
  In order to control coupled bunch oscillations in the SLS storage ring, feedback systems for all three planes were forseen. The filters are realized as fully digital bunch by bunch systems. With the development of dedicated Analog to Digital and Digital to Analog Converter boards, the feedbacks could be commissioned. Important parts of the computations for the transverse planes could be implemented into the ADC FPGA, making the DSPs originally planned to be used obsolete and allowing for an extremely low latency time of 200 ns. The systems give a larger freedom in the choice of the beam optics and also lead to a better closure of the injection bump during top up mode.  
 
TUPMA016 Computation of Wakefields and Impedances for the PETRA III Longitudinal Feedback Cavity impedance, simulation, scattering, kicker 124
 
  • A. K. Bandyopadhyay, A. Joestingmeier, A. S. Omar
    Otto-Von-Guericke University, Magdeburg
  • K. Balewski, R. Wanzenberg
    DESY, Hamburg
  At DESY the existing PETRA II storage ring will be converted into a 3rd generation synchrotron radiation source, called PETRA III. The total beam current is limited by coupled bunch instabilities, which are mainly driven by the parasitic modes of the RF cavities. It is planned to use longitudinal and transverse feedback systems to achieve the design current of 100 mA. Eight single cell feedback cavities will be installed into the PETRA III ring to damp the coupled bunch longitudinal phase oscillations. It is important to know the contribution of the feedback cavity to the impedance budget of PETRA III. In this article, the wake and impedance computation results, using the loss and kick parameters, will be reported. The computer codes MAFIA and Microwave Studio have been used to compute the electromagnetic fields.  
 
WEZH101 Real Time Feedback on Beam Parameters controls, coupling, synchrotron, collider 295
 
  • R. J. Steinhagen
    CERN, Geneva
  Traditionally, tight beam parameter stability requirements were most pronounced for light sources and lepton colliders but became increasingly important for present and future hadron accelerator operation, not only for performance but also for reasons of machine protection, as recent improvements lead to significantly increased stored beam energies. In the latest generation machines the performance depends critically on the stability of the beam. In order to counteract disturbances due to magnetic imperfections, misalignments, ground motion, temperature changes and other dynamic effects, fully automated control of the key beam parameters –- orbit, tune, coupling, chromaticity and energy -– becomes an increasingly important aspect of accelerator operation. This contribution presents an overview of beam-based feedback systems, their architecture, performance limitations and design choices involved.

invited oral

 
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WEC3H101 Multi-bunch Feedback Activities at Photon Factory Advanced Ring kicker, injection, betatron, controls 330
 
  • W. X. Cheng, T. Obina
    KEK, Ibaraki
  The photon factory advanced ring (PF-AR) is a dedicated single bunch light source at KEK, however, some users require multi-bunch operation for high intensity x-ray beams. The old transverse damping system can suppress only one (or two) bunches, while new multi-bunch feedback system has been successfully tested to a maximum of 64 bunches. Both analog and digital transverse feedback loop has been tested at AR to store multi-bunches. Long cables are used to delay the bunch position error signal from BPM buttons for analog feedback control loop. Betatron phase advance between stripline kicker and BPM are selected to be around 90 deg. For digital feedback loop, it based on a FPGA test board. Bunch position error signal sampled by ADC, filtered by 10-tap FIR filter implemented in FPGA and send to DAC output for correction. FIR filter is well designed to increase the system dynamic range. Digital delay can also be implemented inside FPGA instead of long cable delays. Maximum beam current of 97mA has been achieved for several bunches’ storage, betatron oscillation of the stored beam can be suppressed well.  
 
WEPMA050 BPM (Beam Position Monitor) in the PAL Linac and BTL linac, electron, pick-up, controls 393
 
  • S.-C. Kim, J. Choi, Y. J. Han, J. Y. Huang, D. T. Kim, W. W. Lee, H. J. Park
    PAL, Pohang, Kyungbuk
  In Aug. 2004, thirteen BPMs are installed at BTL (Beam Transport Line), and later in Aug. 2005, three BPM installed at main linac for beam trajectory measurement and feedback. BPMs for the BTL consist of 100mm strip-line electrodes in 150mm long chamber and uses SMA-R type feed-throughs. BPMs of the Linac consist of 57mm strip-line electrodes in 100mm short chamber and SMA-R type feed-throughs. 500MHz log-ratio signal processing circuits are used for the Linac and BTL BPM electronics. BPM data acquisition system is developed as an EPICS IOC by using NI S-series DAQ board and NI LabView 7.1. Best read-out accuracy of BPM system is measured as 20mm including BPM electronics. In this paper, we describe on the status of the BPM and its characteristics for PAL Linac and BTL.  
 
WEPMA054 Photon Beam Position Monitor with Hydraulic Level System storage-ring, photon, diagnostics, controls 398
 
  • Y. J. Han, J. Choi, J. Y. Huang, S. N. Kim, Y.-C. Kim
    PAL, Pohang, Kyungbuk
  • I. S. Ko
    POSTECH, Pohang, Kyungbuk
  In a synchrotron radiation source like the Pohang Light Source (PLS), a great effort has been made on beam stability improvements. For the beamline user-sided orbit feedback, Photon Beam Position Monitor(PBPM) provides more practical informations on the position and angle of the electron beam at the center of the bending magnet, compared the closed orbit data. For improvement of the orbit stability, PBPMs are used in PLS. However, as the ground of PLS moves about 2mm every year, we also monitor the level difference between the storage ring and the beamline floor with Hydraulic Level System (HLS). The design and experimental results of PBPM with HLS will be presented.  
 
WEPMA070 Control of the Multi-Bunch Instabilities at TLS kicker, controls, synchrotron, synchrotron-radiation 419
 
  • C. H. Kuo, J. Chen, K. T. Hsu, S. Y. Hsu, K. H. Hu, D. Lee
    NSRRC, Hsinchu
  To increase stored beam current and provide stable beam for users, RF is upgraded to superconducting and top-up mode injection is operated recently at the TLS. To take advantage of these upgrade, suppress multi-bunch instabilities due to resistive wall of the vacuum chamber, cavity-like structures and ions related instability are essential. FPGA based transverse bunch-by-bunch feedback system and longitudinal feedback system was deployed. Multi-bunch instabilities was successfully suppressed when stored beam current is more than 400 mA. Lower chromaticity operation is possible with the help of transverse feedback system that is essential for injection efficiency improvement in top-up operation mode. Status of the feedback systems and analysis of the behavior of multi-bunch instability will be presented.  
 
WEPMA071 The Design, Fabrication and Performance Testing of the Analog I/Q RF Control System at NSRRC controls, klystron, booster, linac 422
 
  • M.-S. Yeh, L.-H. Chang, F.-T. Chung, Y.-H. Lin, Ch. Wang
    NSRRC, Hsinchu
  An analog low-level RF system, based on an I/Q modulator and demodulator, has been tested at NSRRC. The I/Q RF control system has the same function blocks as the digital low-level RF system, which we plan to develop for our proposed 3-GeV light source machine. This analog I/Q RF system provides a real function structure to verify the working principle, block functions and performance evaluation of the developing digital low-level RF system. This work presents the designed function diagrams, the measured results for the characteristics of the main RF components, and the performance testing of the analog I/Q RF control system with a dummy cavity.  
 
WEPMA103 The Design And Performance of the Prototype Digital Feedback RF Control System For the PLS Storage Ring controls, linac, resonance, proton 464
 
  • I. H. Yu, J. Y. Huang, H.-S. Kang, D. T. Kim, H. Y. Kim, S.-C. Kim, I. S. Park
    PAL, Pohang, Kyungbuk
  The digital feedback RF control system for the Proton Engineering At the Pohang Light Source (PLS) Storage Ring, the low level RF system based on analog technique provides RF field control for the 4 RF stations, and each station drives each RF cavity at 500.082MHz. To achieve better control system stability and accuracy, the prototype digital feedback RF control has been developed in Pohang Accelerator Laboratory (PAL). In addition to RF field control, it provides cavity resonance control, and incorporates the personnel and machine protection functions. An accelerator electric field stability of ± 0.5% in amplitude and ± 0.5° in phase is required for the RF system. In order to accomplish these requirements, a digital feedback control technique is adopted for flexibility of the feedback and feed forward algorithm implementation. In this paper, the design and performance of this system will be presented with the performance test results.  
 
WEPMA120 Development of the Digital RF Control System for the PEFP Proton Accelerator controls, simulation, proton, beam-loading 488
 
  • H. S. Kim, Y.-S. Cho, I.-S. Hong, H.-J. Kwon, K. T. Seol, Y.-G. Song
    KAERI, Daejon
  The low level RF system is under development for the PEFP Proton Accelerator. The RF amplitude and phase stability requirements of the LLRF system are ±1% and ±1°, respectively. As a prototype of the LLRF, a simple digital PI control system based on commercial FPGA board is designed and tested. The main features are a sampling rate of 40 MHz which is four times higher than the down-converted cavity signal frequency, digital in-phase and quadrature detection, pulsed mode operation with the external trigger, and a simple proportional-integral feedback algorithm. The control logic is implemented in the Xilinx FPGA by using VHDL coding and the application program based on the VxWorks and VME platform is also developed. In this paper, the detailed design study and the test results of the prototype LLRF system are presented.  
 
THYMA03 Commissioning Experience of Superconducting Radio Frequency Systems for the Taiwan Light Source cryogenics, vacuum, synchrotron, photon 549
 
  • Ch. Wang, L.-H. Chang, M. H. Chang, S.-S. Chang, F.-T. Chung, F. Z. Hsiao, M.-C. Lin, Y.-H. Lin, M. H. Tsai, T.-T. Yang, M.-S. Yeh
    NSRRC, Hsinchu
  An industrially manufactured CESR-type SRF module has been routinely operated at the Taiwan Light Source (TLS) at the National Synchrotron Radiation Research Center (NSRRC) since the beginning of March 2005. The original goals of doubling the electron beam current to increase the synchrotron light intensity and of eliminating the instability caused by the interaction of the electron beams with the cavity's higher-order modes have been successfully demonstrated. The greatest challenge to the operational reliability is the shortness of the mean time between failures, and has been successfully overcome. This work reports the commissioning experience of the SRF module at TLS for high beam-current operation toward a maximum beam current of 400 mA in top-up mode from 200 mA in decay mode over last two years. Emphasized will be the instrument development for analysis of SRF trip event and the continuous improvements of the operating analogous low-level rf system against instability of feed back loops caused by heavy beam loading.  
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THYMA05 Low-level RF Control System Design and Architecture controls, simulation, klystron, linac 559
 
  • L. R. Doolittle
    LBNL, Berkeley, California
  Low-level RF (LLRF) control hardware and its embedded programming plays a pivotal role in the performance of an accelerator. Modern designs implement most of the signal processing in the digital domain. This reduces the size and cost of the hardware, but places the burden of proper operation on the programming. FPGAs (field programmable gate arrays) and communications-grade ADCs and DACs enable sub-microsecond group delay for the LLRF controller feedback signal. Ancient concepts of the virtue of simplicity are easy to apply to the hardware, but more of a challenge in the context of programming. Digital signal processing, combined with dedicated hardware, can control and maintain cavity phase (relative to an absolute reference) unaffected by drift or 1/f noise of any long cables or active components. Developing and testing that programming is a very real challenge. This paper discusses approaches and techniques to make LLRF systems meet their goals in upcoming accelerators.  
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THZMA01 Status of SOLEIL Project vacuum, storage-ring, controls, insertion 578
 
  • L. S. Nadolski, J. C. Besson, P. Brunelle, A. Buteau, L. Cassinari, M.-E. Couprie, J.-C. Denard, J.-M. Filhol, C. Herbeaux, J.-F. Lamarre, V. Le Roux, P. Lebasque, A. Lestrade, M.-P. Level, A. Loulergue, A. Madur, P. Marchand, A. Nadji, R. Nagaoka, B. Pottin, J. B. Pruvost, F. Ribeiro, M.-A. Tordeux
    SOLEIL, Gif-sur-Yvette
  SOLEIL, the 2.75 GeV new French Synchrotron Radiation Facility, located near Paris, is under commissioning. Here are reported the first main results obtained on the storage ring. The beam dynamics characterisation of the 3.7 nm.rad optics is presented, as well as the first measurements of the instability thresholds. Furthermore comparison is made with expectations of the linear optics model and instability calculations. First experience with innovative devices and technologies is also presented: TANGO control system, BPM system, extensive use of NEG coating vessels, RF system (Solid state amplifiers, and superconducting cavities). Six insertion devices accommodating a wide energy range from 5 eV to 50 keV (in-vacuum, Apple II, large period electromagnetic types) are now installed on the machine and some of them are giving the first photon beam to the beamlines. Finally a roadmap towards beam delivery to users will be presented (orbit stability, beam filling patterns, top-up operation).  
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THZMA04 Status and Future of Taiwan Light Source injection, emittance, storage-ring, synchrotron 602
 
  • K. S. Liang, J.-R. Chen, C.-C. Kuo, G.-H. Luo, D.-J. Wang
    NSRRC, Hsinchu
  The Taiwan Light Source of National Synchrotron Radiation Research Center (NSRRC) has reached a very stable operation condition and productive scientific outputs. The copper Doris RF cavities were replaced with a niobium Superconducting (SC) RF cavity in order to eliminate higher-order-modes and deliver higher beam current. Superconducting wigglers were installed to provide higher flux at higher photon energy. The storage ring is now operated at 300 mA top-up mode with better than 97 % of beam availability during users shifts. The original layout of the magnets has been greatly modified to accommodate one SC wavelength shifter at the injection section, one SC wiggler at the RF cavity section, and three SC wigglers in achromatic sections in addition to the original design of one wiggler and three undulators. In view of the future scientific demands, the NSRRC is proposing to construct a new synchrotron storage ring of 3.0~3.3 GeV and ultra low emittance, the Taiwan Photon Source (TPS). The TPS will provide brilliant X-rays at 1021 photons/s/0.1%BW /mm2/mr2 by SC undulator upon its completion, making it the brightest synchrotron light with the finest performance in the world.  
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THPMA024 Implementation of High Precision Magnet Power Supply using the DSP controls, power-supply 666
 
  • K.-H. Park, J. Choi, C. W. Chung, S.-H. Jeong, D. E. Kim
    PAL, Pohang, Kyungbuk
  • B.-K. Kang
    POSTECH, Pohang, Kyungbuk
  This paper presents the precision magnet power supply for the Pohang Light Source using the digitally controlled PWM method. The required current to energize the some magnets was 600 A with the high precision of ~10ppm at least to accomplish a high stable beam operation. This power supply has been implemented using a digital signal processor, TMS320F28 series from Texas Instruments, with high speed external 16-bit ADCs. The designed digital controller includes both a current feedback loop and a DC link voltage feed-forward loop, which was applied by the PI control scheme. To reduce the output current ripple, the damped L-C filter was fabricated at both the DC link and load sides. Various experimental results such as stability, bandwidth and harmonic analysis, as well as simulation are given to verify the characteristics of the DSP based magnet power supply.  
 
THPMA028 Regulation Scheme for Precision Magnet Power Supply power-supply, controls, antiproton, monitoring 669
 
  • S. Bandyopadhyay, M. Das
    DAE/VECC, Calcutta
  Accelerators require extremely precise high-current magnet power supplies to drive their magneto-optic devices for proper beam dynamics. The dc precision of the power supply, which generally defines the absolute tolerance of its current, can be split up into three distinct parts — ripple, short-term and long-term stability. To ensure that the output current is within an error-band of 10ppm or less, a three-loop regulation topology has been developed and implemented in a high current magnet power supply (750A/12V) that uses transistor bank as the series pass element.  
 
THPMA032 Active Filter for Harmonic Mitigation for Magnet Power Supplies of INDUS-II impedance, power-supply, controls, resonance 671
 
  • Y. P. Singh, S. Kotaiah, A. C. Thakurta
    RRCAT, Indore (M. P.)
  Power supplies used for powering of magnets in INDUS-I and INDUS-II uses different type of power converters including SMPS and thyristorised power converters. Though considerations are given to keep the harmonic loading on a.c. mains low while designing these power supplies and selecting a suitable power converter for the required power, still they give a significant amount of harmonic loading on a.c. mains. In all the high power d.c. power supplies, wide variation in operating point leads to a considerable amount of reactive power generation and harmonic loading on ac mains. In this work a study has been performed to know the variation of reactive power with time on some of the d.c. power supplies of INDUS-II. Various options to improve the power factor has been studied and their advantages & limitations for accelerator magnet power supplies has been highlighted. A combined system of a shunt passive and small rated series active filter has been proposed. The compensation principle is described and filtering characteristics are discussed in detail. A scale down prototype of proposed series active filter has been developed in lab and experimental results produced.  
 
THPMA033 Digital Power Supply Development at the PLS power-supply, controls, simulation, booster 674
 
  • K. M. Ha, J. H. Kim
    PAL, Pohang, Kyungbuk
  Digital power supply controller using the Digital Signal Processor (DSP) and Field Programmable Gate Array (FPGA) has been developed over the year at the Pohang Light Source (PLS). Recently, full digital power supply controller has been completed and tested. A new digital controller is designed as 3U euro-standard size and provides overall performance of the power supplies stability better than 5 ppm short-term stability (< 1 min) and 25 ppm long-term stability (< 12 hours). The digital controller made use of the digital PID current controller with one-pole digital filter and feed-forward voltage ripple compensation control algorithms. By implementation of the digital controller, it is capable of high step resolution (150 ps) Digital Pulse Width Modulation (DPWM) for FET or IGBT switch drivers and high resolution (18-bit, 400 kSPS) analog to digital converter (ADC) for current and voltage signal measurements. In this paper the hardware and software structure of the developed digital controller and experimental results of digital power supply are described.

Pohang Accelerator Laboratory, Pohang, 790-784, Korea* This works supported by the Ministry of Science and Technology, Korea.

 
 
THPMA047 Stair Current Output Power Supply for Switching Magnet controls, power-supply, quadrupole, electron 691
 
  • S.-H. Jeong, J. Choi, H.-S. Kang, D. E. Kim, K.-H. Park
    PAL, Pohang, Kyungbuk
  The switching magnet for beam distribution to 5 beamlines of 20-MeV PEFP is served with DSP-controlled PWM switching-mode converter. This converter is employed IGBT module and a DSP (Digital Signal Processor) that is operated at ?350A, 2.5 Hz stair output. Current feedback and input voltage feed-forward control schemes are applied to improve the output current stability. Designed filter result in the good stability of each stair. Simulation and experimental results show that the implemented converter achieves stable repeat response at each stair and feasibility for versatile power supply.  
 
THPMA063 Energy Stabilization of 2.5 GeV Linac using DeQing linac, controls, klystron, power-supply 717
 
  • S. H. Kim, Y. J. Han, J. Y. Huang, S.-C. Kim, S. H. Nam, S. S. Park
    PAL, Pohang, Kyungbuk
  The 2.5 GeV electron linac of Pohang Accelerator Laboratory (PAL) employs 80 MW klystrons with matching 200 MW modulators as RF sources. Beam voltage stability of the klystron is directly related to a PFN (pulse forming network) charging voltage of the modulator. Therefore, a good regulation of a PFN charging voltage is essential in the modulator. The regulation of the klystron pulse voltage amplitude is made by controlling the PFN charging voltage. In a conventional resonant charging pulse modulator, the regulation is usually achieved by using a deQing circuit. The required beam voltage regulation of less than ± 0.5 %, without deQing circuit, has been achieved by using a SCR phase controller with a voltage regulator. For further improvement of the beam voltage stability for the PAL XFEL (x-ray free electron laser) linac, PAL is studying a deQing circuit aiming at the stabilization of less than 0.02%. A new deQing circuit has been developed with a compensation function which can reduce a charge voltage fluctuation by about several times. The design concept and performance of the deQing circuit will be discussed.  
 
THPMA074 Operational Analysis of Klystron-Modulator System for PLS 2.5-GeV Electron Linac klystron, linac, electron, controls 740
 
  • S. S. Park, J. Y. Huang, S. H. Kim, S.-C. Kim
    PAL, Pohang, Kyungbuk
  The klystron-modulator(K&M) system of the Pohang Accelerator Laboratory (PAL) generates high power microwaves for the acceleration of 2.5 GeV electron beams. There are 12 modules of K&M system to accelerate electron beams up to 2.5 GeV nominal beam energy. One module of the K&M system consists of the 200 MW modulator and an 80 MW S-band (2856 MHZ) klystron tube. The total accumulated high-voltage run-time of the oldest unit among the 12 K&M systems has reached nearly 92,300 hours as of June 2006. The overall system availability is well over 95%. In this paper, we review overall system performance of the high-power K&M system and the operational status of the klystrons and thyratron lifetimes, and overall system's availability will be analyzed for the period of 1994 to June 2006.  
 
THPMA102 The Proton and Ion Linear Accelerator ILU-9 ion, acceleration, proton, cathode 788
 
  • A. A. Bryazgin, V. Auslender, V. G. Cheskidov, B. L. Faktorovich, E. Konstantinov, A. D. Panfilov
    BINP SB RAS, Novosibirsk
  The pulse RF ion linear accelerator of ILU-9-type is described. The accelerator is intended to use for various radiation-technological processes and investigations. The main parameters of the accelerator are: energy of accelerated protons 2.9 or 5 (with additional accelerating section) MeV, energy of accelerated deutons 5.8 or 10 MeV, average current of accelerated ions up to 100 μA. Pulse operating mode as following: pulse duration-500 s, maximum pulse repetition- 50 Hz. The frequency of accelerator resonator is 43 MHz. Also data of carbon ions C12+4 acceleration probability are given.