Keyword: damping
Paper Title Other Keywords Page
SUPB025 Development of Superconducting Radio-Frequency (SRF) Deflecting Mode Cavities and Associated Waveguide Dampers for the APS Upgrade Short Pulse X-Ray Project cavity, HOM, photon, cryomodule 65
 
  • J.P. Holzbauer, A. Nassiri, G.J. Waldschmidt, G. Wu
    ANL, Argonne, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CHI1357.
The Advanced Photon Source Upgrade (APS-U) is a Department of Energy (DoE) funded project to increase the available x-ray beam brightness and add capability to enhance time-resolved experiments on few-ps-scale at APS. A centerpiece of the upgrade is the generation of short pulse x-rays (SPXs) for pump-probe time-resolved capability using SRF deflecting cavities[1]. The SPX project is designed to produce 1-2 ps x-ray pulses for some users compared to the standard 100 ps pulses currently produced. SPX calls for using superconducting rf (SRF) deflecting cavities to give the electrons a correlation between longitudinal position in the bunch and vertical momentum [2]. The light produced by this bunch can be passed through a slit to produce a pulse of light much shorter than the bunch length at reduced flux. The ongoing work of designing these cavities and associated technologies will be presented. This includes the design and prototyping of higher-order (HOM) and lower-order mode (LOM) couplers and dampers as well as the fundamental power coupler (FPC). This work will be given in the context of SPX0, a demonstration cryomodule with two deflecting cavities to be installed in APS in early 2014.
[1] A. Zholents, et al., NIM A 425, 385 (1999)
[2] A. Nassiri, et al., “ Status of the Short-Pulse X-Ray Project at the Advanced Photon Source,” IPAC 2012, New Orleans, LA, May 2012.
 
 
SUPB039 Compact Superconducting Crabbing and Deflecting Cavities cavity, dipole, HOM, collider 95
 
  • S.U. De Silva
    ODU, Norfolk, Virginia, USA
  • S.U. De Silva
    JLAB, Newport News, Virginia, USA
 
  Recently, new geometries for superconducting crabbing and deflecting cavities have been developed that have significantly improved properties over those the standard TM110 cavities. They are smaller, have low surface fields, high shunt impedance and, more importantly for some of them, no lower-order-mode with a well-separated fundamental mode. This talk will present the status of the development of these cavities.  
 
MOPLB08 Normal Conducting Deflecting Cavity Development at the Cockcroft Institute cavity, beam-loading, wakefield, electron 159
 
  • G. Burt, P.K. Ambattu, A.C. Dexter, C. Lingwood, B.J. Woolley
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • S.R. Buckley, P. Goudket, C. Hill, P.A. McIntosh, J.W. McKenzie, A.E. Wheelhouse
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • A. Grudiev
    CERN, Geneva, Switzerland
  • R.M. Jones
    UMAN, Manchester, United Kingdom
 
  Funding: This work has been supported by STFC and the EU through FP7 EUCARD.
Two normal conducting deflecting structures are currently being developed at the Cockcroft Institute, one as a crab cavity for CLIC and one for bunch slice diagnostics on low energy electron beams for EBTF at Daresbury. Each has its own challenges that need overcome. For CLIC the phase and amplitude tolerances are very stringent and hence beamloading effects and wakefields must be minimised. Significant work has been undertook to understand the effect of the couplers on beamloading and the effect of the couplers on the wakefields. For EBTF the difficulty is avoiding the large beam offset caused by the cavities internal deflecting voltage at the low beam energy. Propotypes for both cavities have been manufactured and results will be presented.
 
slides icon Slides MOPLB08 [1.572 MB]  
 
MOPB031 Vibration Response Testing of the CEBAF 12 GeV Upgrade Cryomodules cryomodule, cavity, controls, beam-loading 240
 
  • G.K. Davis, J. Matalevich, T. Powers, M. Wiseman
    JLAB, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The CEBAF 12 GeV upgrade project includes 80 new 7-cell cavities assembled into 10 cryomodules. These cryomodules were tested during production to characterize their microphonic response in situ. For several early cryomodules, detailed (vibration) modal studies of the cryomodule string were performed during the assembly process to identify the structural contributors to the measured cryomodule microphonic response. Structural modifications were then modeled, implemented, and verified by subsequent modal testing and in-situ microphonic response testing. Interim and final results from this multi-stage process will be reviewed.
 
 
MOPB043 Detailed Analysis of the Long-Range Wakefield in the Baseline Design of the CLIC Main Linac wakefield, HOM, factory, impedance 270
 
  • V.F. Khan, A. Grudiev
    CERN, Geneva, Switzerland
 
  The baseline design for the accelerating structure of the CLIC main linac relies on strong damping of transverse higher order modes (HOMs). Each accelerating cell is equipped with four damping waveguides that enables HOM energy to propagate to damping loads. Most of the HOMs decay exponentially with a Q-factor of about 10 however, there are modes with higher Q-factors. Though the amplitude of the high Q modes is nearly two orders of magnitude smaller than the dominating lowest dipole mode, their cumulative effect over the entire bunch train may be significant and dilute the beam emittance to unacceptable level. In this paper we report on an accurate calculation of the long-range wakefield and its overall effect on beam dynamics. We also discuss possible measures to minimise its effect in a tapered structure.  
 
MOPB055 Development of Superconducting Radio-Frequency (SRF) Deflecting Mode Cavities and Associated Waveguide Dampers for the APS Upgrade Short Pulse X-Ray Project cavity, HOM, photon, cryomodule 300
 
  • J.P. Holzbauer, A. Nassiri, G.J. Waldschmidt, G. Wu
    ANL, Argonne, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CHI1357.
The Advanced Photon Source Upgrade (APS-U) is a Department of Energy (DoE) funded project to increase the available x-ray beam brightness and add capability to enhance time-resolved experiments on few-ps-scale at APS. A centerpiece of the upgrade is the generation of short pulse x-rays (SPXs) for pump-probe time-resolved capability using SRF deflecting cavities[1]. The SPX project is designed to produce 1-2 ps x-ray pulses for some users compared to the standard 100 ps pulses currently produced. SPX calls for using superconducting rf (SRF) deflecting cavities to give the electrons a correlation between longitudinal position in the bunch and vertical momentum [2]. The light produced by this bunch can be passed through a slit to produce a pulse of light much shorter than the bunch length at reduced flux. The ongoing work of designing these cavities and associated technologies will be presented. This includes the design and prototyping of higher-order (HOM) and lower-order mode (LOM) couplers and dampers as well as the fundamental power coupler (FPC). This work will be given in the context of SPX0, a demonstration cryomodule with two deflecting cavities to be installed in APS in early 2014.
[1] A. Zholents, et al., NIM A 425, 385 (1999)
[2] A. Nassiri, et al., “ Status of the Short-Pulse X-Ray Project at the Advanced Photon Source,” IPAC 2012, New Orleans, LA, May 2012.
 
 
MOPB079 Normal Conducting Deflecting Cavity Development at the Cockcroft Institute cavity, beam-loading, wakefield, electron 357
 
  • G. Burt, P.K. Ambattu, A.C. Dexter, C. Lingwood, B.J. Woolley
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • S.R. Buckley, P. Goudket, C. Hill, P.A. McIntosh, J.W. McKenzie, A.E. Wheelhouse
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • A. Grudiev
    CERN, Geneva, Switzerland
  • R.M. Jones
    UMAN, Manchester, United Kingdom
 
  Funding: This work has been supported by STFC and the EU through FP7 EUCARD.
Two normal conducting deflecting structures are currently being developed at the Cockcroft Institute, one as a crab cavity for CLIC and one for bunch slice diagnostics on low energy electron beams for EBTF at Daresbury. Each has its own challenges that need overcome. For CLIC the phase and amplitude tolerances are very stringent and hence beamloading effects and wakefields must be minimised. Significant work has been undertook to understand the effect of the couplers on beamloading and the effect of the couplers on the wakefields. For EBTF the difficulty is avoiding the large beam offset caused by the cavities internal deflecting voltage at the low beam energy. Propotypes for both cavities have been manufactured and results will be presented.
 
 
WE1A02 Status and Future of the CLIC Study linac, luminosity, emittance, target 719
 
  • R. Corsini
    CERN, Geneva, Switzerland
 
  The Compact Linear Collider (CLIC) International Collaboration is carrying out an extensive R&D program towards a multi-TeV electron-positron collider. The CLIC concept is based on the use of high-gradient normal-conducting accelerating structures in conjunction with a novel two-beam acceleration scheme, where the RF power needed to accelerate the colliding beams is extracted from a high-current drive beam running parallel to the main linac. In order to establish the feasibility of such concept a number of key issues were addressed, both experimentally and theoretically, and the results of the study were documented in the recently completed CLIC Conceptual Design Report (CDR). The conclusions reached in the CDR constitute also an important contribution to the European strategy group. A short summary of the present status with will be given, together with an outlook on the program for the next period, aimed at the preparation of an implementation plan.  
 
WE2A01 RF Power Production at the Two Beam Test Stand at CERN recirculation, acceleration, target, extraction 738
 
  • I. Syratchev
    CERN, Geneva, Switzerland
 
  The generation of short (250 ns) high peak power (135 MW) RF pulses by decelerating the high current (100 A) bunched (12 GHz) drive beam is one of the key components in the CLIC two beam acceleration scheme. Recent tests with drive beam deceleration at CERN's CTF3, using specially developed 1 m long CLIC Power Extraction and Transfer Structure (PETS) operated in re-circulation regime have successfully demonstrated this concept. The results of these tests are presented.  
slides icon Slides WE2A01 [2.636 MB]  
 
TH1A02 Compact Superconducting Crabbing and Deflecting Cavities cavity, dipole, HOM, collider 753
 
  • S.U. De Silva
    ODU, Norfolk, Virginia, USA
  • S.U. De Silva
    JLAB, Newport News, Virginia, USA
 
  Recently, new geometries for superconducting crabbing and deflecting cavities have been developed that have significantly improved properties over those the standard TM110 cavities. They are smaller, have low surface fields, high shunt impedance and, more importantly for some of them, no lower-order-mode with a well-separated fundamental mode. This talk will present the status of the development of these cavities.  
slides icon Slides TH1A02 [3.811 MB]  
 
THPLB07 Experience with a 4-Rod CW Radio Frequency Quadrupole rfq, ion, linac, resonance 825
 
  • P. Gerhard, W.A. Barth, L.A. Dahl, W. Hartmann, G. Schreiber, W. Vinzenz, H. Vormann
    GSI, Darmstadt, Germany
 
  Since 1991 the High Charge State Injector (HLI) provides heavy ion beams for the linear accelerator UNILAC at GSI*. It is equipped with an ECR ion source and an RFQ-IH linac which accelerates highly charged ion beams with high duty factor of up to 30% to 1.4 MeV/u for further acceleration in the Alvarez DTL of the UNILAC. Main user of these beams is the Super Heavy Element (SHE) research, one of the outstanding projects at GSI**. Experiments like TASCA and SHIP strongly benefit from the high average beam intensities. After two decades of successful operation the four-rod Radio Frequency Quadrupole (RFQ) accelerator was replaced in 2010 by a newly designed RFQ of the same type**. Besides higher beam transmission, the principal intention of this upgrade was to raise the duty factor up to 100%, since the HLI is foreseen as injector for the upcoming cw linac dedicated to the SHE program**. Commissioning and operational experience from the first years revealed that this goal could not be reached easily. In this paper we present the RFQ design, commissioning results, operational experience and future activities.
* N. Angert et al., EPAC92, Berlin, Germany (1992), p. 167
** L. Dahl et al., LINAC10, Tsukuba, Japan (2010), MOP042, and references therein
 
slides icon Slides THPLB07 [0.986 MB]  
 
THPB035 Experience with a 4-Rod CW Radio Frequency Quadrupole rfq, ion, linac, resonance 930
 
  • P. Gerhard, W.A. Barth, L.A. Dahl, W. Hartmann, G. Schreiber, W. Vinzenz, H. Vormann
    GSI, Darmstadt, Germany
 
  Since 1991 the High Charge State Injector (HLI) provides heavy ion beams for the linear accelerator UNILAC at GSI*. It is equipped with an ECR ion source and an RFQ-IH linac which accelerates highly charged ion beams with high duty factor of up to 30% to 1.4 MeV/u for further acceleration in the Alvarez DTL of the UNILAC. Main user of these beams is the Super Heavy Element (SHE) research, one of the outstanding projects at GSI**. Experiments like TASCA and SHIP strongly benefit from the high average beam intensities. After two decades of successful operation the four-rod Radio Frequency Quadrupole (RFQ) accelerator was replaced in 2010 by a newly designed RFQ of the same type**. Besides higher beam transmission, the principal intention of this upgrade was to raise the duty factor up to 100%, since the HLI is foreseen as injector for the upcoming cw linac dedicated to the SHE program**. Commissioning and operational experience from the first years revealed that this goal could not be reached easily. In this paper we present the RFQ design, commissioning results, operational experience and future activities.
* N. Angert et al., EPAC92, Berlin, Germany (1992), p. 167
** L. Dahl et al., LINAC10, Tsukuba, Japan (2010), MOP042, and references therein