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beam-loading

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MOPCH118 Wideband Low-output-impedance RF System for the Second Harmonic Cavity in the ISIS Synchrotron impedance, synchrotron, controls, acceleration 321
 
  • Y. Irie
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • D. Bayley, G.M. Cross, I.S.K. Gardner, M.G. Glover, D. Jenkins, A. Morris, A. Seville, S.P. Stoneham, J.W.G. Thomason, T. Western
    CCLRC/RAL/ISIS, Chilton, Didcot, Oxon
  • J.C. Dooling, D. Horan, R. Kustom, M.E. Middendorf, G. Pile
    ANL, Argonne, Illinois
  • S. Fukumoto, M. Muto, T. Oki, A. Takagi, S. Takano
    KEK, Ibaraki
  Wideband low-output-impedance RF system for the second harmonic cavity in the ISIS synchrotron has been developed by the collaboration between Argonne National Laboratory, US, KEK, Japan and Rutherford Appleton Laboratory, UK. Low output impedance is realized by the feedback from plate output to grid input of the final triode amplifier, resulting in less than 30 ohms over the frequency range of 2.7 - 6.2 MHz which is required for the second harmonic cavity. The vacuum tubes in the driver and final stages are both operated in class A, and a grid bias switching system is used on each tube to avoid unnecessary plate dissipations during a non-acceleration cycle. High power test was performed with a ferrite-loaded second harmonic cavity, where the bias current was swept at 50 Hz repetition rate. The maximum voltage of 12kV peak per accelerating gap was obtained stably at earlier period of an acceleration cycle. A beam test with this system is planned at the ISIS synchrotron in order to investigate how the low impedance system works under heavy beam loading conditions, and is capable of mitigating the space charge detuning at the RF trapping stage.  
 
MOPCH138 Choice of Proton Driver Parameters for a Neutrino Factory target, proton, factory, acceleration 372
 
  • W.-T. Weng, J.S. Berg, R.C. Fernow, J.C. Gallardo, H.G. Kirk, N. Simos
    BNL, Upton, Long Island, New York
  • S.J. Brooks
    CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
  A Neutrino Factory typically comprises the following subsystems: proton driver; target; muon collection and conditioning( bunching, phase rotation, and cooling); muon acceleration; and muon decay ring. It takes great effort to design each subsystem properly, such that it can mesh with all other subsystems to optimize the overall facility performance. This optimization is presently being studied as part of the International Scoping Study of a Future Neutrino Factory and Superbeam Facility. This paper will evaluate the implications of other subsystems on the parameters of a proton driver for a Neutrino Factory. At the desired power of 4 MW, the impacts of the choice of the proton energy, bunch length, bunch intensity, and repetition rate on other subsystems are assessed to identify a proper range of operation for each parameter. A suitable "design phase space" of proton driver parameters is defined. Given possible choices of design parameters for proton driver, we compare the performance of a linac, a synchrotron, and an FFAG accelerator. The relative merits of existing proton driver proposals will also be examined.  
 
TUPCH112 Commissioning of the 100 MeV Preinjector HELIOS for the SOLEIL Synchrotron emittance, linac, gun, SOLEIL 1274
 
  • A.S. Setty, D. Jousse, J.-L. Pastre, F. Rodriguez
    THALES, Colombes
  • R. Chaput, J.-P. Pollina, B. Pottin, M.-A. Tordeux
    SOLEIL, Gif-sur-Yvette
  • A. Sacharidis
    EuroMev, Buc
  HELIOS is the 100 MeV electron linac pre-injector of SOLEIL the new French SR facility. It has been supplied by THALES, as a turn-key system on the basis of SOLEIL APD design. The linac was commissioned in October 2005. This paper will remind the main features of the linac, especially on beam-loading compensation, and will give results obtained during the commissioning tests where a special care has been taken for emittance measurements. Specified and measured beam parameters will be compared to show the performance of the entire system.  
 
TUPCH117 Experience with the 208MHz and 52MHz RF Systems for the HERA Proton Accelerator feedback, controls, DESY, injection 1289
 
  • R. Wagner, S. Choroba, A. Gamp, T.G. Grevsmuehl, G.M. Moeller
    DESY, Hamburg
  • A.B. Bienkowski
    The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
  The RF System for the Hera Proton Ring consists of four 208MHz systems and two 52MHz systems. At injection three of the 208MHz systems are at 70 kV and one System is at 190kV with a phase of 180 degree. The 52 MHz Systems are at 70kV each. During ramping the RF voltage of all cavities follows a ramp table. At flat top at 920GeV both 52 MHz systems are at 50kV and three of the 208MHz Systems are at 190kV while the 180 degree phased system is reduced to 30kV. The typical beam current is 100mA in 180 bunches with a bunch separation of 96 ns. About one year before shutdown of HERA this presentation gives an review of about 14 years operation of the Proton RF System. It is also an overview of the hardware including the beam loading compensation (fast feedback) the tuning system and the other components.  
 
TUPCH128 New Cutting Scheme of Magnetic Alloy Cores for J-PARC Synchrotrons DIAMOND, synchrotron, acceleration, KEK 1313
 
  • C. Ohmori, S. Anami, E. Ezura, Y. Funahashi, K. Hara, K. Hasegawa, A. Takagi, M. Toda, K. Ueno, M. Yoshii
    KEK, Ibaraki
  • Y. Morita, T. Yoshioka
    ICEPP, Tokyo
  • M. Nomura, A. Schnase, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  A new cutting method using a grindstone was developed to manufacture the magnetic alloy cores. The problem of local temperature rise around the cut surfaces was solved. Long-term high-power tests have been performed for both J-PARC RCS and MR RF systems. Mechanism of local heating, new cutting scheme, and manufacturing method are presented.  
 
TUPCH130 Development of the Feed-forward System for Beam Loading Compensation in the J-PARC RCS FIR, FFC, CIC, controls 1319
 
  • F. Tamura, M. Nomura, A. Schnase, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Yoshii
    KEK, Ibaraki
  In the J-PARC Rapid Cycling Synchrotron (RCS), the heavy beam loading effects due to the high intensity proton beam must be compensated for stable acceleration. The beam feedforward technique is used to compensate the beam loading in the RCS. We present the development of the feedforward system. We designed and built the full-digital system with modern FPGAs to realize high accuracy, stability and predictability of the compensation. Because of the low Q value of each accelerating cavity, the wake voltage consists of not only the accelerating harmonic component but also higher harmonics. Thus, the system is designed to compensate the beam loading at several harmonics. The system has two parts. In the first part, vector components of the selected harmonic are detected from the beam signal picked up by a wall current monitor. The compensation RF signal is generated from the vector components with proper gain and phase in the latter part. The gain and phase are set individually for each harmonic and each cavity of the twelve cavities. We also present the preliminary test results of the newly developed modules.  
 
TUPCH186 Low Level RF System Development for SOLEIL feedback, SOLEIL, simulation, damping 1447
 
  • P. Marchand, M.D. Diop, F. Ribeiro, R.S. Sreedharan
    SOLEIL, Gif-sur-Yvette
  • M. Luong, O. Piquet
    CEA, Gif-sur-Yvette
  The Low Level RF system that is used in the SOLEIL storage ring consists in fully analog "slow" amplitude, phase and frequency loops, complemented with a direct RF feedback. A fast digital FPGA-based I/Q feedback, currently under development, will be implemented later on. The performance of both systems has been evaluated using a Matlab-Simulink-based simulation tool. The computed and first experimental results are reported.  
 
TUPCH190 Universal Controller for Digital RF Control controls, resonance, klystron, feedback 1459
 
  • S. Simrock
    DESY, Hamburg
  • W. Cichalewski, M.K. Grecki, G.W. Jablonski
    TUL-DMCS, Lodz
  • W.J. Jalmuzna
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw
  Digital RF control systems allow to change the type of controller by programming of the algorithms executed in FPGAs and/or DSPs. It is even possible to design a universal controller where the controller mode is selected by change of parameters. The concept of a universal controller includes the self-excited-loop (SEL) and generator driven resonator (GDR) concept, the choice of I/Q and amplitude or phase control, and allows for different filters (including Kalman filter and method of optimal controller synthesis) to be applied. Even time-varying mixtures of these modes are possible. Presented is the implementation of such a controller and the operational results with a superconducting cavity.  
 
THPCH066 Transient Beam Loading in the DIAMOND Storage Ring DIAMOND, simulation, storage-ring, damping 2937
 
  • S. De Santis, J.M. Byrd
    LBNL, Berkeley, California
  • R. Bartolini
    Diamond, Oxfordshire
  Harmonic cavity systems have been installed on several 3rd generation light sources to lengthen the bunches and increase the Touschek lifetime. Apart from this beneficial effect, harmonic cavities are known to increase the transient beam loading in high-current machines, due to the presence of gaps in the fill pattern. The amplitude of this effect, which is substantially larger than that caused by the main RF system, can in turn produce considerable variations in bunch length and phase along the train, which result in a significant reduction of the lifetime increase. We have developed a tracking simulation, which we have applied to the analysis of the beam loading transients in Diamond, for the case of passive superconducting harmonic cavities. The influence of beam current, gap amplitude and harmonic cavity tuning on the final lifetime have been studied, as well as the effects of higher-order modes.  
 
THPLS111 Beam Loading Measurement and its Application to the Harmonic RF Control of the APS PAR synchrotron, injection, controls, photon 3538
 
  • C. Yao, E.E. Cherbak, N.P. Di Monte, A. Grelick, T. Smith, B.X. Yang
    ANL, Argonne, Illinois
  The particle accumulator ring (PAR) has dual rf systems: a CW mode fundamental rf system (RF1) operating at 9.77 MHz that accumulates multiple linac pulses into a 0.8-ns bunch, and a 12th harmonic rf (RF12) that compresses the bunch length further to 0.34 ns for injection into the booster. The RF12 capture process is critical for optimal performance of the PAR. We investigated the effects of beam loading during the RF12 capture and bunch length compression process with both spectrum analysis and streak camera imaging. Based on these observations, a new timing scheme for the RF12 tuner and power control was implemented, which has substantially improved the performance of the PAR. We report our observation, the new timing scheme, and beam parameters after optimization.  
 
THPLS112 Electron Multipacting Observation and Simulation in the APS PAR electron, simulation, vacuum, resonance 3541
 
  • C. Yao, Y.-C. Chae
    ANL, Argonne, Illinois
  The particle accumulator ring (PAR) has both fundamental and 12th harmonic rf systems. Gap voltage fluctuations were experienced after vacuum work was performed on the PAR during a maintenance period. This has caused intermittent beam instability and prevented us from running the PAR fundamental rf system at normal power level. Our investigation has concluded that the problem was caused by electron multipacting in the center vacuum chamber of the cavity. We were able to suppress the multipacting by applying a solenoid field in the suspected region. Computer simulation is underway in order to find the location and the parameter range of the multipacting. In this paper we report the experimental observations and results of the simulation relevant to the phenomena.