Keyword: pick-up
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MOPEA016 The Main Stochastic Cooling System of the HESR kicker, accumulation, vacuum, simulation 100
 
  • R. Stassen, R. Greven, R. Maier, G. Schug, H. Stockhorst
    FZJ, Jülich, Germany
  
  The main stochastic cooling system of the High-Energy Storage Ring HESR (1.5-15 GeV/c) for antiprotons at the FAIR complex (Facility for Antiprotons and Ion Research) in Darmstadt (GSI) will work in the frequency range of 2 - 4 GHz. The design work on pickup and kicker is now finished and the production of the first cooling tank has been started. The whole system layout will be presented taking into account new additional requirements concerning the accumulation and the cooling of heavy ions. All beam-coupling structures are nearly identical and contain several ring-slot blocks. These blocks consist of eight wall-current monitors coupled out by eight electrodes each. Most of the signal combining and splitting take place within the vacuum envelope to reduce the number of vacuum RF feed throughs. The long-distance transmission of the signals and the filters containing long signal delays work with near infrared optical elements.  
 
MOPEA042 Research on the Design and Simulation of the CSRE Stochastic Cooling System sextupole, emittance, target, simulation 169
 
  • X.J. Hu, H. Jia, Y.J. Yuan, X.H. Zhang
    IMP, Lanzhou, People's Republic of China
  
  Stochastic cooling by the use of a feedback system, aims at cooling of secondary particles or particles with large emittance or momentum spread. My research is mainly on the simulation of horizontal and longitudinal stochastic cooling process. The purpose of my work is to obtain the optimum parameters for stochastic cooling, according the actual accelerator lattice. Pickup and preamplifier are already installed on the CSRe, and preliminary results are get.  
 
MOPME013 20 Years of Development of SQUID-based Cryogenic Current Comparator for Beam Diagnostics ion, cryogenics, shielding, niobium 497
 
  • W. Vodel
    HIJ, Jena, Germany
  • R. Geithner, R. Neubert, P. Seidel
    FSU Jena, Jena, Germany
  • K.K. Knaack, K. Wittenburg
    DESY, Hamburg, Germany
  • A. Peters
    HIT, Heidelberg, Germany
  • H. Reeg, M. Schwickert
    GSI, Darmstadt, Germany
  
  This contribution gives an overview on the development of highly sensitive SQUID-based Cryogenic Current Comparators (CCC) for nuclear physics from the first successful demonstration of its performance at GSI Darmstadt through the latest improved version for FAIR and the Cryogenic Storage Ring at MPI Heidelberg. An absolute and exact measurement of the intensity of charged particle beams - extracted from an accelerator or circulating in a Storage Ring - is one of the major problems of beam diagnosis. Also the measurement of so-called dark currents, generated by super-conductive RF accelerator cavities at high voltage gradients to characterize the quality of these components becomes more and more important for the commissioning of new accelerators (XFEL at DESY). The Cryogenic Current Comparator (CCC) based on high precision LTS SQUIDs is an excellent tool to solve these problems.  
 
MOPME042 A PRELIMINARY SIMULATION OF BPM SIGNAL DIODE DETECTOR FOR HLS II TUNE MEASUREMENT SYSTEM* simulation, betatron, storage-ring, synchrotron 565
 
  • J.J. Zheng, P. Lu, T.J. Ma, B.G. Sun, Y.L. Yang, J.Y. Zou
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  Funding: Supported by National Natural Science Foundation of China (11105141, 11175173) and the Fundamental Research Funds for the Central Universities (WK2310000015)
A high sensitivity BPM signal detection front-end electronics has been designed for HLS II tune measurement system according to the HLS II upgrade requirements. Classical tune measurement systems filter out just one or a few of these betatron sidebands frequency. As a consequence, most of the betatron energy is dropped and only a very small energy remains for further processing. A new method, referred to as Direct Diode Detection (3D) by LHC[1], improves the situation. In this paper, the HLS II BPM signals have been calculated out in time domain and frequency domain. Basing on the characteristics of HLS II BPM signal, a preliminary simulation is performed to test and verify the feasibility of diode detector for HLS II tune measurement system. The simulation results clearly show that the technique of diode-based circuit can be applied to HLS II tune measurement. 		 
 
MOPME044 A Novel Type of Forward Coupler Slotted Stripline Pickup Electrode for CSRe Stochastic Cooling impedance, vacuum, kicker, simulation 571
 
  • J.X. Wu, X.J. Hu, M. Li, J.W. Xia, J.C. Yang, Y. Zhang, G. Zhu
    IMP, Lanzhou, People's Republic of China
  • F. Caspers
    CERN, Geneva, Switzerland
  
  A novel type of slotted or perforated strip-line pick-up or kicker electrode structure for CSRe stochastic cooling for non relativistic particle beams with b=v/c values around 0.7 is presented. This slotted structure is to be used as a forward coupler with the output signal taken from the downstream end and has a rather large relative bandwidth of several octaves. The electrode structure and pickup tank, as well as the beam test result will be presented in this paper.  
 
MOPME052 Beam Instrumentation System Optimization for Top-up Operation in SSRF storage-ring, injection, instrumentation, booster 589
 
  • Y.B. Yan, Y.B. Leng, L.Y. Yu, W.M. Zhou
    SINAP, Shanghai, People's Republic of China
  
  In order to offer higher average brightness and more stable photon beam, top-up injection mode is scheduled for daily operation in SSRF. Several critical beam parameters, such as fill pattern, average current, beam lifetime and transfer efficiency, need to be measured precisely and reliably, and few interlock logics need to be added into machine protection system with top-up mode. Hardware and software optimizations of beam instrumentation for this purpose will be introduced in this paper.  
 
MOPME054 Bunch-by-bunch Beam Position and Charge Monitor based on Broadband Scope in SSRF injection, storage-ring, synchrotron, synchrotron-radiation 595
 
  • Y. Yang, Y.B. Leng, Y.B. Yan, N. Zhang
    SSRF, Shanghai, People's Republic of China
  
  A bunch-by-bunch beam position and charge monitor system, based on a broadband oscilloscope, has been developed at SSRF. The beam positions of each bunch could be located independently in this system by using the original signals from the button-type pickups on the storage ring. The relative charge of each bunch could be obtained by the sum signal from the pickups. Using sum weighted average method, turn-by-turn beam position could be got from the bunch-by-bunch beam position data. The difference of each bunch beam position have been observed during injection at SSRF.  
 
MOPME056 Measurement of the Beam Position Monitor’s Electrical Performance and Electronics Sensitivity for 100 MeV Proton Linac and Beam Lines linac, proton, instrumentation, monitoring 598
 
  • J.Y. Ryu, Y.-S. Cho, J.-H. Jang, H.S. Kim, H.-J. Kwon, K.T. Seol
    KAERI, Daejon, Republic of Korea
  
  Funding: This work was supported by the Ministry of Education, Science and Technology of the Korean Government.
The development of the beam position monitor (BPM) is in progress for the 100-MeV proton linac and 10 beam lines of the 1st phase of KOMAC. Those were selected the strip line type BPM for the proton linac and beam lines. 5 beam-line BPMs and 9 linac BPMs were checked their electrical performance in the RF test using by developed test stand and tested the Log-ratio BPM (Beam Position Monitor) electronics module of the Bergoz Instrumentation for direct beam position derivation signal from the pickup signal. After then, those will be installed 100-MeV proton Linac and beam lines for beam commissioning in February 2013. This presentation summarized the results of measured BPM’s electrical performance and the Log-ratio BPM electronics pickup sensitivity. 		 
 
MOPME059 R&D of a Beam Position Monitor for RISP linac, impedance, ion, heavy-ion 607
 
  • E.-S. Kim
    KNU, Deagu, Republic of Korea
  • A. Heo
    Kyungpook National University, Daegu, Republic of Korea
  • H.K. Park
    CHEP, Daegu, Republic of Korea
  
  We have investigated on the R&D of stripline beam position monitor for the heavy-ion accelearator at Korea. We present the detailed design and fabrications on the beam position monitor in superconducting linac that the beam is accelerated to 200 MeV/u.  
 
MOPME073 Measurement of Schottky-like Signals from Linac Bunched Hadron Beams for Momentum Spread Evaluation linac, cavity, synchrotron, bunching 649
 
  • P. Kowina, P. Forck, R. Singh
    GSI, Darmstadt, Germany
  • F. Caspers
    CERN, Geneva, Switzerland
  • R. Singh
    TEMF, TU Darmstadt, Darmstadt, Germany
  
  We present a novel method for the measurement of Linac beam parameters in the longitudinal phase space. The longitudinal momentum spread can be evaluated by means of Schottky type signal analysis of bunched beams. There is a close similarity between a repetitive Linac bunch train and a circulating beam with a single short batch in a large machine like the LHC. A dedicated longitudinal cavity pick-up was used in the Linac where resonance frequency and Q-value were carefully selected in order to get an optimum compromise between the unavoidable coherent signal and the desired incoherent part of the beam spectrum. A time domain gating similar to the 4.8 GHz LHC Schottky front-end is applied. As a cross-check of the validity of the interpretation in terms of momentum spread, the Linac beam is analyzed in the downstream synchrotron using standard Schottky methods. In principle, this approach can be understood as an extension of Schottky analysis for circular machines with a perfect “mixing” between subsequent bunch trains. This contribution describes the test set-up and discusses the results of the measurements with a heavy ion beam.  
 
MOPWA001 Development of a High Precision Integrator for Analog Signals to Measure Magnetic Fields in Realtime synchrotron, ion, controls, feedback 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.  
 
MOPWA037 Commissioning of the CERN Linac4 BPM System with 50 MeV Proton Beams linac, proton, simulation, optics 750
 
  • J. Tan, M. Ludwig, L. Søby, M. Sordet, M. Wendt
    CERN, Geneva, Switzerland
  
  The new Linac4 at CERN will provide a 160 MeV H− ion beam for charge-exchange injection into the existing CERN accelerator complex. Shorted stripline pick-ups placed in the Linac intertank regions and the transfer lines will measure beam orbit, relative beam current, beam phase, and average beam energy via the time-of-flight between two beam pickups. A prototype Beam Position Monitor (BPM) system has been installed in the transfer line between the existing Linac2 and the Proton Synchrotron Booster (PSB) in order to study and review the complete acquisition chain. This paper presents measurements and performance of this BPM system operating with 50 MeV proton beams, and compares the results with laboratory measurements and electromagnetic simulations.  
 
MOPWA050 Bunch Train Characterisation for an Infra-red FEL Driven by an Energy Recovery Linac FEL, electron, EPICS, diagnostics 786
 
  • T.T. Thakker, D. Angal-Kalinin, D.J. Dunning, F. Jackson, S.P. Jamison, J.K. Jones, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  The IR-FEL on the ALICE test facility in the UK first achieved lasing in October 2010 and has since been characterised in terms of its output *. In this work we make a characterisation of electron bunch properties along a complete 100us macropulse to characterise the lasing-induced energy change and its effect on energy recovery. Measurements of bunch energy and timing are correlated with the FEL radiation output and discussed.
* N. R. Thompson et al, ‘First lasing of the ALICE infra-red Free-Electron Laser’, Nuclear Instruments and Methods A, 680 (2012) 117–123 		 
 
MOPWA067 Robust High-average-power Modulator controls, klystron, neutron, power-supply 834
 
  • I. Roth, N. Butler, M.P.J. Gaudreau, M.K. Kempkes
    Diversified Technologies, Inc., Bedford, Massachusetts, USA
  
  Funding: US DOE. Grant No. DE-SC0004254
Diversified Technologies Inc. (DTI) designed a modulator which meets the requirements of the Spallation Neutron Source (SNS) modulators at Oak Ridge National Laboratory and will be less expensive than copies of the current modulators. The SNS modulators, under development for a decade, still do not meet the specifications for voltage, droop, or pulsewidth. The modulators must provide pulses of 85 kV, 165 A, with pulsewidths of 1.5 ms and voltage flatness of 1%. The current modulator switches the full power at high frequency during each pulse, and has a complex output transformer. DTI designed a modulator that meets all specifications and is less expensive. The proposed design is cheaper because there is an HV switch that operates at full current only once per pulse, a corrector that switches only 5% of the power at high frequency, a low-cost transformer-rectifier power supply, and no output transformer. DTI’s patented switch uses IGBTs, allowing the switch to operate at full capacity even if 20% of the devices fail. The modulator will be installed in 2013 at SNS to test klystrons. DTI will present the system components of the design as well as the performance results to date. 		 
 
MOPWA070 Beam Position Monitor within the Cornell Energy Recovery Linac Cavity Assembly HOM, coupling, RF-structure, cavity 840
 
  • M.G. Billing, M. Liepe, V.D. Shemelin, N.R.A. Valles
    CLASSE, Ithaca, New York, USA
  
  In an energy recovery Linac (ERL) the low energy beam is very sensitive to deflections due to the RF fields as it passes through the accelerator cavities. Therefore, to avoid the possible effects of beam breakup, it will be important to determine the optimum transverse position for the beam within the first several sets of cavity cells in the cryostat assembly and to maintain this position over long periods. As a result a beam position monitor (BPM) has been designed to be located between the higher-order modes (HOM) loads and the seven-cell RF structures. This BPM’s design reduces the coupling of RF power from the fundamental mode and HOMs into the BPM, while maintaining acceptable position sensitivity and resolution. We analyzed the coupling of the probe to the HOMs of realistically shaped cavities by generating geometries for hundreds of cavities having small shape variations from the nominal dimensions consistent with present machining tolerances, and solved for their monopole and dipole spectra. Our results show that the peak, dissipated power within BPM cables, which pass through the cryostat, is well within the permissible levels.  
 
MOPWA071 A Comparison of Electron Cloud Density Measurements at CesrTA electron, simulation, positron, resonance 843
 
  • J.P. Sikora, J.A. Crittenden, D.O. Duggins, Y. Li, X. Liu
    CLASSE, Ithaca, New York, USA
  • S. De Santis
    LBNL, Berkeley, California, USA
  
  Funding: This work is supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the US Department of Energy DE-FC02-08ER41538, DE-SC0006505.
Several techniques have been employed to measure the electron cloud (EC) density in accelerators. These include Time Resolved Retarding Field Analyzers (TR-RFA) and Shielded Pickups (SPU) that measure the flux of cloud electrons onto the beam-pipe wall, as well as TE wave resonance techniques that measure the EC density in a region within the volume of the beam-pipe. We have made measurements to test the EC mitigation properties of different surface coatings and geometries, often with more than one technique used in the same test chamber. We present a comparison of bare aluminum chambers with those having a TiN coating, as well as the effect of beam conditioning. In addition, we will compare the results of the different measurement techniques used in the same chamber. These measurements were made at the Cornell Electron Storage Ring (CESR) which has been reconfigured as a test accelerator (CesrTA) having positron or electron beam energies ranging from 2 GeV to 5 GeV. 		 
 
MOPWA072 MODELING FOR TIME-RESOLVED RETARDING FIELD ANALYZER MEASUREMENTS OF ELECTRON CLOUD BUILDUP AT CesrTA electron, vacuum, positron, dipole 846
 
  • J.A. Crittenden, Y. Li, X. Liu, M.A. Palmer, J.P. Sikora
    CLASSE, Ithaca, New York, USA
  
  Funding: US National Science Foundation PHY-0734867, PHY-1002467, and the U.S. Department of Energy DE-FC02-08ER41538
The Cornell Electron Storage Ring Test Accelerator program includes investigations into electron cloud buildup mitigation techniques using custom vacuum chambers. Multibunch electron and positron beams of energies between 2.1 and 5.3 GeV with bunch spacings from 4 to 98 ns and bunch populations ranging from 1010 to 16·1010 provide highly differentiated sensitivity to the processes contributing to cloud buildup such as photoelectron production, cloud space-charge dynamics, and secondary electron emission. Measurements of the time dependence of cloud buildup using BPM-style shielded pickups have been shown to provide tight constraints on cloud buildup models. Recently, time-resolving retarding-field analyzers have been designed, installed and commissioned. These novel detectors combine the time-resolving feature of the shielded pickups with the fine transverse segmentation and cloud electron energy sensitivity of the time-integrating retarding-field analyzers used previously. We report on progress in modeling these measurements and quantify their sensitivity to various parameters describing the underlying physical processes contributing to cloud buildup. 		 
 
TUPFI068 High Power Tests of Alumina in High Pressure RF Cavities for Muon Ionization Cooling Channel cavity, collider, resonance, klystron 1508
 
  • L.M. Nash
    University of Chicago, Chicago, Illinois, USA
  • G. Flanagan, R.P. Johnson, F. Marhauser, J.H. Nipper
    Muons. Inc., USA
  • M.A. Leonova, A. Moretti, M. Popovic, A.V. Tollestrup, K. Yonehara
    Fermilab, Batavia, USA
  • Y. Torun
    IIT, Chicago, Illinois, USA
  
  It is important to make a compact muon ionization cooling channel to increase the cooling efficiency (muon survival rate, cooling decrement, etc). A proposed scheme to reduce the radial size of RF cavities at a given resonance frequency is to insert a dielectric material into the RF cavity. In vacuum cavities, however, dielectric materials are extremely susceptible to breakdown in high power conditions. High-pressure hydrogen gas has been shown to inhibit breakdown events in RF cavities in strong magnetic fields. An experiment has been designed to test surface breakdown of alumina in RF cavities. A structure has been designed to maximize the parallel field parallel to the surface while bringing the cavity into a desired frequency range (800-810MHz). Alumina is tested in this configuration under high power conditions. The experimental result will be shown in this presentation.  
 
TUPME039 The Drive Beam Phase Stability in CTF3 and its Relation to the Bunch Compression Factor linac, acceleration, klystron, linear-collider 1655
 
  • E. Ikarios, A. Andersson, J. Barranco, B. Constance, R. Corsini, A. Gerbershagen, T. Persson, P.K. Skowroński, F. Tecker
    CERN, Geneva, Switzerland
  
  The proposed Compact Linear Collider (CLIC) is based on a two-beam acceleration scheme. The energy needed to accelerate a low intensity "main" beam is provided by a high intensity, low energy "drive" beam. The precision and stability of the phase relation between two beams is crucial for the performance of the scheme. The tolerable phase jitter is 0.2 deg rms at 12GHz. For this reason it is fundamental to understand the main possible causes of the drive beam timing jitter. Experimental work aimed at such understanding was done in the CLIC Test Facility (CTF3) where a drive beam with characteristics similar to the CLIC one is produced. Several phase measurements allowed us to conclude that the main source of phase jitter is energy jitter of the beam transformed and amplified into phase jitter when passing through a magnetic chicane. This conclusion is supported by measurements done with different momentum compaction values in the chicane. In this paper the results of these several phase measurements will be presented and compared with expectations.  
 
TUPME061 Emittance Growth with Crab Cavity and Damper Noise in LHC emittance, simulation, resonance, damping 1706
 
  • S. Paret, J. Qiang
    LBNL, Berkeley, California, USA
  
  Funding: This work was partially supported by the U.S. LARP and the NERSC of the U.S. Department of Energy under contract No. DE-AC02-05CH11231.
Strong-strong beam-beam simulations are employed to investigate the noise sensitivity of the emittance in the future High Luminosity (HL)-LHC. Noise in the accelerator causes fluctuations of the bunch centroids at the interaction points (IPs) which cause emittance growth for large beam-beam parameters. Two noise sources are examined: Crab cavities and the transverse damper. The damper noise is adjusted to bring simulations in agreement with an emittance measurement in a past LHC run. Results from simulations with HL-LHC beam parameters using different noise levels, damper gains and working points are discussed. 		 
 
WEOBB203 Design of Phase Feed Forward System in CTF3 and Performance of Fast Beam Phase Monitors kicker, optics, quadrupole, target 2097
 
  • P. Skowroński, A. Andersson, A. Gerbershagen, E. Ikarios, J. Roberts
    CERN, Geneva, Switzerland
  • P. Burrows, G.B. Christian, A. Gerbershagen, C. Perry, J. Roberts
    JAI, Oxford, United Kingdom
  • P. Burrows, G.B. Christian, A. Gerbershagen, C. Perry
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
  • A. Ghigo, F. Marcellini
    INFN/LNF, Frascati (Roma), Italy
  • E. Ikarios
    National Technical University of Athens, Athens, Greece
  
  Funding: Work supported by the European Commission under the FP7 Research Infrastructures project Eu- CARD, grant agreement no. 227579
The CLIC two beam acceleration technology requires a drive beam phase stability of better than 0.3 deg rms at 12 GHz, corresponding to a timing stability below 50 fs rms. For this reason the CLIC design includes a phase stabilization feed-forward system. It relies on precise beam phase measurement and its subsequent correction in a chicane with help of fast kickers. A prototype of such a system is being installed in CLIC Test Facility CTF3. In this paper we describe in detail its design and implementation. Additionally, we present and discuss the performance of the precision phase monitor prototypes installed at the end of the CTF3 linac, measured with the drive beam.
We would like to acknowledge support of G.Sensolini, A.Zolla (INFN/LNF Frascati), N.S.Chritin and J-M.Scigliuto (CERN) in design and fabrication of components. 		 
slides icon Slides WEOBB203 [6.770 MB]  
 
WEPWO001 Power Couplers for XFEL vacuum, site, controls, monitoring 2310
 
  • W. Kaabi, M. El Khaldi, A. Gallas, P. Lepercq, C. Magueur, A. Variola, A. Verguet
    LAL, Orsay, France
  • W.-D. Möller
    DESY, Hamburg, Germany
  
  The LAL contribution to the XFEL project will be the delivery of 800 power couplers to equip 100 Cry-modules. The LAL’s tasks consist on the industrial monitoring and coupler quality control at two different production sites, in addition to the RF conditioning at LAL of the 800 produced couplers. The RF conditioning and all the coupler preparation process will be held in a 70m2 ISO5 clean room. An RF power station delivering 5MW, allow 8 couplers conditioning in the same time. Being in production control side and also RF conditioning one, the aim of LAL is to reach the rate of 8 couplers delivery per week, after a rump up phase. The starting of Coupler mass production is scheduled for beginning 2013.  
 
WEPWO012 XFEL 3.9 GHz Prototype Cavities Tests cavity, HOM, status, diagnostics 2337
 
  • P. Pierini, M. Bertucci, A. Bosotti, C. Maiano, P. Michelato, L. Monaco, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • E.R. Harms
    Fermilab, Batavia, USA
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • E. Vogel
    DESY, Hamburg, Germany
  
  In preparation for the XFEL components production, three prototype cavities have been manufactured and vertically tested at INFN-LASA. Several tests, with and without HOM antennas and in a double cavity test configuration, have been performed. Further tests of one of the prototypes took place at FNAL, to validate results between the two test facilities. Results were consistent with those obtained at INFN-LASA.  
 
WEPWO046 First Test Results of the 4-rod Crab Cavity cavity, vacuum, niobium, coupling 2405
 
  • R. Calaga, L.S. Alberty Vieira, S. Calatroni, O. Capatina, E. Ciapala, L.M.A. Ferreira, E. Jensen, P. Maesen, A. Mongelluzzo, T. Renaglia, M. Therasse
    CERN, Geneva, Switzerland
  • P.K. Ambattu, D. Doherty, B.D.S. Hall, C. Lingwood
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • G. Burt
    Lancaster University, Lancaster, United Kingdom
  
  Funding: The HiLumi LHC Design Study (a sub-system of HL-LHC) is cofunded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.
The first prototype crab cavity with the 4-rod geometry has undergone surface treatment and cold testing. Due to the complex geometry and unique fabrication procedure, RF validation of the field at beyond the nominal operating voltage at a sufficiently high Q0 is an important pre-requiste. Preliminary results of the first cold tests are presented along with cavity performance at different stages of the cavity processing is described. 		 
 
WEPWO084 Improvement of the Q-factor Measurement in RF Cavities cavity, dipole, coupling, HOM 2489
 
  • W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn
    BNL, Upton, Long Island, New York, USA
  • S.A. Belomestnykh, I. Ben-Zvi
    Stony Brook University, Stony Brook, USA
  
  Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S.
The Q values of Higher-order-modes (HOMs) in RF cavities are measured at room temperature with the 3 dB bandwidth reading by a network analyzer. The resonant curve distortion is created by the resonance splitting due to the ellipticity caused by manufacture tolerance and RF ports. Therefore, the measured Q values are usually lower than the simulated or theoretical Q values. In some cases, even only one mode’s Q can be measured with the 3 dB method. There may be two reasons for this happening. One is that only one mode was excited and the neighbor splitmode was close to 90° polarized; the other reason is that the resonant curve of one mode was distorted by the other mode too much to measure the 3dB range. In this paper, we resolve this issue by looking into the RF measurement setup, including cavity, input coupler and pick-up coupler, from the equivalent circuit and wave point of view. Based on the BNL3 copper prototype cavity, we compared these results from measurement and simulation. 		 
 
WEPFI016 Upgrade of Power Supply System for RF-Chopper At J-PARC Linac linac, cavity, LLRF, simulation 2735
 
  • K. Futatsukawa, Z. Fang, Y. Fukui, M. Ikegami, T. Miyao
    KEK, Ibaraki, Japan
  • E. Chishiro, K. Hirano, Y. Ito, N. Kikuzawa, A. Miura, F. Sato, S. Shinozaki
    JAEA/J-PARC, Tokai-mura, Japan
  • T. Hori
    JAEA, Ibaraki-ken, Japan
  • Y. Liu, T. Maruta
    KEK/JAEA, Ibaraki-Ken, Japan
  • T. Suzuki
    Mitsubishi Electric System & Service Co., Ltd, Tsukuba, Japan
  
  In the J-PARC Linac, the radio frequency deflector was adopted as a chopper to capture the particles into the RF-bucket in the next synchrotron. The chopper, consists of two deflectors, was installed on the medium-energy beam-transport line. In the operation of the RF-chopper, the fast rise/fall time of the pulse is a fundamental requirement to minimize the beam loss due to insufficient deflection to some beam bunches. In the previous system, the two series-connected chopper deflectors were driven by one solid- state amplifier. However, the fall time indicated a poor result to effect the ringing into each cavity. Therefore, the additional solid-state amplifier and low level RF system were installed in the summer 2012 and the connection changed to the parallel system from the series using two amplifiers. The rise/fall time of the chopped beam, is defined as the step height of 10% and 90%, was about 20 nsec in the beam current of 15 mA and the effect of the ringing was decreased. We would like to introduce the performance of the new chopper system.  
 
WEPFI017 Performance of Cavity Phase Monitor at J-PARC Linac cavity, linac, DTL, LLRF 2738
 
  • K. Futatsukawa, S. Anami, Z. Fang, Y. Fukui, T. Kobayashi, S. Michizono
    KEK, Ibaraki, Japan
  • F. Sato, S. Shinozaki
    JAEA/J-PARC, Tokai-mura, Japan
  
  The amplitude and the phase stabilities of the RF system play an important role for the cavity of a high intensity proton accelerator. For the J-PARC Linac, the accelerating field ambiguity must be maintained within ±1% in amplitude and ±1 degree in phase due to the momentum acceptance of the next synchrotron. To realize the requirement, a digital feedback (FB) control is used in the low level RF (LLRF) control system, and a feed-forward (FF) technique is combined with the FB control for the beam loading compensation. The stability of ±0.2% in amplitude and ±0.2 degree in phase of the cavity was achieved including the beam loading in a macro pulse. Additionally, the cavity phase monitors, which can measure the phase difference between any two cavities, were installed in summer, 2011. The monitor has the three different types, which are for the present 324-MHz RF system, the 972-MHz RF system and the combined system of 324-MHz RF and 972-MHz RF. The phase monitor for the 324-MHz RF has been in operated since Dec. 2011. We would like to introduce the phase monitor and indicate the phase stability at the J-PARC linac.  
 
WEPME006 Optical Synchronization and Electron Bunch Diagnostic at ELBE laser, electron, feedback, 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.  
 
WEPME014 Progress in Development of New LLRF Control System for SuperKEKB cavity, controls, klystron, LLRF 2953
 
  • T. Kobayashi, K. Akai, K. Ebihara, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri
    KEK, Ibaraki, Japan
  • H. Deguchi, K. Harumatsu, K. Hayashi, T. Iwaki, J. Mizuno, J. Nishio, M. Ryoshi
    Mitsubishi Electric TOKKI Systems, Amagasaki, Hyogo, Japan
  
  For the SuperKEKB project, a new LLRF control system was developed to realize high accuracy and flexibility. It is an FPGA-based digital RF feedback control system using 16-bit ADC's, which works on the μTCA platform. The FPGA boards control accelerating cavity fields and cavity tuning, and the EPICS-IOC is embedded in each of them. The CSS-BOY was adopted for a user interface of our system. High power test of the new LLRF control system was performed with the ARES Cavity of KEKB. The obtained feedback control stability with a klystron drive was sufficient as well as the low-level evaluation result. And auto tuner control also worded successfully. The start-up sequencer program for the cavity operation and auto-aging program also worked very well. The temperature characteristics of the system depend largely on band-pass filters (BPF). We tried to tune the BPF to reduce the temperature coefficient. Consequently the temperature dependence was improved to satisfy the required stability.  
 
WEPME042 Modelling and Studies for a Wideband Feedback System for Mitigation of Transverse Single Bunch Instabilities feedback, kicker, 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, feedback, injection, kicker 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.  
 
WEPME056 Application of Z-transform to Noise Response Modeling of a Bunch-by-bunch Feedback System feedback, storage-ring, lattice, 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 feedback, controls, 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. 		 
 
THOAB101 Laser Wire Based Parallel Profile Scan of H− Beam at the Superconducting Linac of Spallation Neutron Source laser, ion, neutron, linac 3090
 
  • Y. Liu, A.V. Aleksandrov, D.L. Brown, R. Dickson, C. Huang, C.D. Long
    ORNL, Oak Ridge, Tennessee, USA
  • C.C. Peters
    ORNL RAD, 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.
We report on the world’s first experiment of a parallel profile scan of the hydrogen ion (H−) beam using a laser wire system. The system was developed at the superconducting linac (SCL) of the Spallation Neutron Source (SNS) accelerator complex. The laser wire profile scanner is based on a photo-detachment process and therefore can be conducted on an operational H− beam in a nonintrusive manner. The parallel profile scanning system makes it possible to simultaneously measure profiles of the 1-MW neutron production H− beam at 9 different locations (corresponding to energy levels of 400 – 950 MeV) of the superconducting linac using a single light source. The entire measurement process takes less than 5 minutes to complete. Together with the hardware modification, we have also upgraded our user interface to visualize the 9-pairs of H− beam profiles in a real-time fashion, which presents a highly intuitive and informative picture of the H− beam propagation along the acceleration path. The laser wire based parallel profile scanning system provides a powerful tool for accelerator operators and physicists to study the SCL modelling, monitor and/or tune the beam parameters. 		 
slides icon Slides THOAB101 [2.277 MB]  
 
THPFI003 Vacuum Study of the Cavity String for the IFMIF - LIPAc Cryomodule vacuum, cryomodule, cavity, linac 3291
 
  • N. Bazin, G. Devanz, F. Orsini
    CEA/DSM/IRFU, France
  
  In the framework of the International Fusion Materials Irradiation Facility (IFMIF), a superconducting option has been chosen for the 5 MeV RF Linac of the first phase of the project (EVEDA), based on a cryomodule composed of 8 HWRs, 8 RF couplers and 8 Solenoid packages. This paper will focus on the beam vacuum of the cryomodule. The cryomodule beam line is made of the pattern solenoid package / cavity-coupler, and a valve on each side of the cryomodule. During the installation of the cryomodule on the accelerator system, the cavity string has to be pumped down with the beam valves closed. Thereby a manifold is connected to the cavities during the assembly of the beam line components in the clean room. In previous conferences, the cryomodule was presented with a vacuum manifold connected to each cavity. A study realized on this complex vacuum configuration with Molflow, a test-particle Monte-Carlo simulator for ultra-high vacuum, permitted to reduce the number of cavities connected to the manifold and by consequence to reduce the risk of pollution during the clean room assembly.  
 
THPFI023 A Newly Developed High Directivity X-band Waveguide Directional Coupler simulation, coupling, insertion, vacuum 3345
 
  • X. He, X. Wang, F. Zhao
    IHEP, Beijing, People's Republic of China
  
  A new X-band waveguide directional coupler working at 11.9924 GHZ is designed. Four holes symmetrical to the structure is drilled along the central line of the narrow-wall, which is used to couple the electromagnetic power from the main-waveguide to the sub-waveguide. The final prototype has got a measurement result of 32.2 dB Directivity (-47.0 dB Coupling Degree) together with a very low VSWR (1.067) and Insertion Loss (-0.11 dB) at 11.9924 GHz. The vacuum performance is also qualified.  
 
THPFI047 Design Guidelines for Ferrite Absorbers Submitted to RF-induced Heating radiation, damping, HOM, FEL 3394
 
  • A. Bertarelli, M. Garlaschè
    CERN, Geneva, Switzerland
  
  The use of ferrite absorbers is one of the most effective means of damping potentially harmful high order RF modes, which may lead to beam instabilities and excessive power losses in accelerator devices. However, the power deposited on ferrite absorbers themselves may lead to ferrite exceeding its Curie temperature, losing its damping properties. An evaluation of the ferrite capability to dissipate deposited heat is hence of paramount importance for the safe design of particle accelerator devices. In this paper, figures of merit are proposed to assess the maximum specific power allowed on a generic ferrite tile, before it reaches its Curie temperature. Due to its inherent brittleness, sufficient contact pressure between ferrite and its housing, allowing heat transmission by conduction, can hardly be applied. A semi-analytical study is thus performed, assuming that ferrite is evacuating heat solely through radiation. The described method is then exemplified in the case of the BPM-embedded tertiary collimator (TCTP) designed in the framework of the LHC collimation upgrade.  
 
THPFI060 Development, Validation and Application of a Novel Method for Estimating the Thermal Conductance of Critical Interfaces in the Jaws of the LHC Collimation System radiation, collimation, target, luminosity 3430
 
  • I. Leitão
    CERN, Geneva, Switzerland
  
  The motivation for this project arises from the difficulty in quantifying the manufacturing quality of critical interfaces in the water cooled jaws of the TCTP and TCSP (Target Collimator Tertiary Pickup and Target Collimator Secondary Pickup) collimators. These interfaces play a decisive role in the transfer of heat deposited by the beam towards the cooling system avoiding excessive deformation of the collimator. Therefore, it was necessary to develop a non-destructive method that provides an estimation of the thermal conductance during the acceptance test of the TCTP and TCSP jaws. The method is based on experimental measurements of temperature evolution and numerical simulations. By matching experimental and numerical results it is possible to estimate the thermal conductance in several sections of the jaw. A simplified experimental installation was built to validate the method, then a fully automatic Test-Bench was developed and built for the future acceptance of the TCTP/TCSP jaws which will be manufactured and installed in the LHC. This novel method has shown its validity and has become a decisive tool for the development of the new generation of LHC collimators.  
 
THPFI063 Development and Beam Tests of an Automatic Algorithm for Alignment of LHC Collimators with Embedded BPMs alignment, controls, collimation, insertion 3439
 
  • G. Valentino
    University of Malta, Information and Communication Technology, Msida, Malta
  • R.W. Aßmann
    DESY, Hamburg, Germany
  • R. Bruce, M. Gasior, D. Mirarchi, A.A. Nosych, S. Redaelli, B. Salvachua, N.J. Sammut
    CERN, Geneva, Switzerland
  
  Collimators with embedded Beam Position Monitor (BPM) buttons will be installed in the LHC during the upcoming long shutdown period. During the subsequent operation, the BPMs will allow the collimator jaws to be kept centered around the beam trajectory. In this manner, the best possible beam cleaning efficiency and machine protection can be provided at unprecedented higher beam energies and intensities. A collimator alignment algorithm is proposed to center the jaws automatically around the beam. The algorithm is based on successive approximation, as the BPM measurements are affected by non-linearities, which vary with the distance between opposite buttons, as well as the difference between the beam and the jaw centers. The successful test results, as well as some considerations for eventual operation in the LHC are also presented.  
 
THPFI088 Electron Cloud Diagnostic Chambers with Various EC-suppression Coatings vacuum, electron, positron, ion 3496
 
  • Y. Li, J.V. Conway, X. Liu, M.A. Palmer
    CLASSE, Ithaca, New York, USA
  
  Funding: Work supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the U.S. Department of Energy DE-FC02-08ER41538
Suppression of electron cloud (EC) growth and density is critical for many high intensity accelerators of positively charged particles, such as positron rings for Super KEKB and ILC’s positron damping ring. Among various suppression techniques, passive coating with low secondary electron emission (SEY) coefficient is the most economic method. During CesrTA EC study program, we have created two dedicated short sections in the CESR vacuum system to study effectiveness of various SEY reduction coatings. During last 4 years, six one-meter-long EC study vacuum chambers were constructed, and rotated through these short sections. The EC chambers were not only equipped with EC diagnostics (including a RFA and RF-shield pickups), they were also installed in CESR with vacuum instrument, including a cold cathode ion gauge and a residual gas analyzer. With these EC study chambers, EC-suppression effectiveness of TiN, amorphous carbon and diamond-like carbon coatings were evaluated, relative to bare aluminum chamber. In this report, we will report vacuum properties of these coatings. In particular, the photon-induced desorption and beam conditioning histories are presented. 		 
 
THPWA043 Production of the FETS RFQ rfq, vacuum, alignment, simulation 3726
 
  • P. Savage, M. Aslaninejad, J.K. Pozimski
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
  • M. Dudman, D.S. Wilsher
    STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
  • A. Garbayo
    AVS, Eibar, Gipuzkoa, Spain
  • A.P. Letchford
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  
  The Front End Test Stand (FETS) project at RAL will use a 324 MHz 4-vane Radio Frequency Quadrupole (RFQ) to accelerate H− ions from 65keV to 3 MeV. This paper will report on the current status of the production of the FETS RFQ and will detail the manufacturing strategy used to produce the major and minor vanes. In addition the inspection results will be shown and the experiences from the assembly and alignment operations will be shared. Finally, the design of the bead-pull apparatus, end flanges, tuners and pick-ups required to measure the frequency and field-flatness of the assembled RFQ will be discussed.  
 
THPWO018 Power Tests of the 325 MHz 4-ROD RFQ Prototype rfq, cavity, impedance, simulation 3800
 
  • B. Koubek, H. Podlech, A. Schempp, J.S. Schmidt
    IAP, Frankfurt am Main, Germany
  
  For the FAIR project of GSI as part of the proton linac a 325 MHz RFQ with an output energy of 3 MeV is planned. Simulations that have lead to a prototype of a 4-Rod Radio Frequency Quadrupole (RFQ) have been done. The RF parameters have been verified with the prototype. Power tests of this 6 stem copper RFQ should now verify parameters like shunt impedance, electrode voltage and give answers of how much power the structure can sustain.