Author: Li, Z.
Paper Title Page
WEPPC021 Development of Superconducting Radio Frequency Cavities at SINAP 2248
  • J.F. Liu, H.T. Hou, C.W. Lu, C. Luo, Z.Y. Ma, D.Q. Mao, J. Shi, Zh.G. Zhang, S.J. Zhao, X. Zheng
    SINAP, Shanghai, People's Republic of China
  • Z.Q. Feng, Z. Li, J.F. Liu, Y.L. Wei, K. Xu, Y.B. Zhao
    Shanghai KEY Laboratory of Cryogenics & Superconducting RF Technology, Shanghai, People's Republic of China
  • H. Yu
    Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
  This paper presents the development of superconducting radio frequency cavities at Shanghai Institute of Applied Physics (SINAP) mainly focused on the 500MHz band. Firstly, Two KEKB type 500MHz single cell niobium cavities have been fabricated and one of them has been vertical tested successfully in 2010. The highest accelerating gradient of the fabricated cavity higher than 10MV/m was obtained while the quality factor was better than 4·108 at 4.2K. Secondly, a new type of 500MHz single cell cavity has been designed which adopts the fluted beam pipe for higher order modes propagation and a coaxial type high power input coupler. Thirdly, a 500MHz 5-cell superconducting cavity with large aperture, enlarged beam pipe for HOM propagation and high r/Q value has been optimized which can be a candidate cavity for high current FEL and ERL.  
MOPPC096 Multiphysics Applications of ACE3P 361
  • K.H. Lee, C. Ko, Z. Li, C.-K. Ng, L. Xiao
    SLAC, Menlo Park, California, USA
  • G. Cheng, H. Wang
    JLAB, Newport News, Virginia, USA
  Funding: Work supported by US DOE Offices of HEP, ASCR and BES under contract AC02-76SF00515.
The TEM3P module of ACE3P, a parallel finite-element electromagnetic code suite from SLAC, focuses on the multiphysics simulation capabilities, including thermal and mechanical analysis for accelerator applications. In this pa- per, thermal analysis of coupler feedthroughs to supercon- ducting rf (SRF) cavities will be presented. For the realistic simulation, internal boundary condition is implemented to capture RF heating effects on the surface shared by a di- electric and a conductor. The multiphysics simulation with TEM3P matched the measurement within 0.4%.
TUPPD078 A Novel Design of a High Brightness Superconducting RF Photoinjector Gun Cavity 1581
  • F. Marhauser, R. Rodriguez
    MuPlus, Inc., Newport News, USA
  • Z. Li
    SLAC, Menlo Park, California, USA
  Funding: Work supported under U.S. DOE Grant Application Number 98802B12-I
Next generation electron accelerators for research, medical, defense or industrial use are in need of electron sources operating at high repetition rates of 1 MHz and beyond, with normalized emittance of 1 mm-mrad or less and bunch charges as much as one nC or more. A conceptual layout of a novel superconducting RF photoinjector gun cavity (SRF gun) is proposed, which can provide unprecedented flexibility to vary beam pulse patterns in the MHz regime and beyond at average currents around 1 mA. It does not require an opening in the center of the back wall and avoids the complex cathode exchange system, but still allows an exchange or refurbishment of the cathode. The demountable back plate has the major benefit to clean the cavity cells independently from the back wall carrying a superconductive photocathode. This mitigates risks of cavity contamination and eases fabrication and chemical post-processing to achieve high accelerating fields, a key parameter to guarantee high brightness beams.
TUPPR037 Simulations of Higher Order Modes in the ACC39 Module of FLASH 1900
  • I.R.R. Shinton, R.M. Jones, P. Zhang
    UMAN, Manchester, United Kingdom
  • Z. Li
    SLAC, Menlo Park, California, USA
  This study is primarily focused on the dipole component of the multiband expansion of the wakefield, with the emphasis being on the development of a HOM-based BPM system for ACC39 currently installed and in operation at FLASH and due to be installed at XFEL . Coupled inter-cavity modes are simulated together with a limited band of trapped modes. A suite of finite element computer codes (including HFSS and ACE3P) and globalised scattering matrix calculations (GSM) are used to investigate the modes in these cavities. In this way the nature of the multi-cavity nature of these modules is investigated with implications for a HOM-based BPM system and direct comparison to experimental results.  
WEEPPB010 RF Modeling Using Parallel Codes ACE3P for the 400-MHz Parallel-Bar/Ridged-Waveguide Compact Crab Cavity for the LHC HiLumi Upgrade 2185
  • Z. Li, L. Ge
    SLAC, Menlo Park, California, USA
  • J.R. Delayen, S.D. Silva
    ODU, Norfolk, Virginia, USA
  Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515.
Schemes utilizing crab cavities to achieve head-on beam-beam collisions were proposed for the LHC HiLumi upgrade. These crabbing schemes require that the crab cavities be compact in order to fit into the tight spacing available in the existing LHC beamlines at the location where the crab cavities will be installed. Under the support of US LARP program, Old Dominion University and SLAC have joint efforts to develop a 400-MHz compact superconducting crab cavity to meet the HiLumi upgrade requirements. In this paper, we will present the RF modeling and analysis of a parallel-bar/ridged-waveguide shaped 400-MHz compact cavity design that can be used for both the horizontal and vertical crabbing schemes. We will also present schemes for HOM damping and multipacting analysis for such a design.
WEPPC068 Multipacting Simulation and Analysis for the FRIB β = 0.085 Quarter Wave Resonators using Track3P 2366
  • L. Ge, C. Ko, Z. Li
    SLAC, Menlo Park, California, USA
  • J. Popielarski
    FRIB, East Lansing, Michigan, USA
  Funding: Work supported by DOE Office of Science under Cooperative Agreement DE- SC0000661, DOE Contract No. DE-AC02-76SF00515, and used resources of NERSC supported by DOE Contract No. DE-AC02- 05CH11231.
The drive linac for the Facility for Rare Isotope Beams (FRIB) utilizes several types of low beta superconducting resonators to accelerate the ion beams from 0.3 MeV per nucleon to 200 MeV per nucleon. Multipacting is an issue of concern for such superconducting resonators as they have unconventional shapes. We have used the parallel codes Tack3P and Omega3P, developed at SLAC under the support of the DOE SciDAC program, to analyze the multipacting barriers of such resonators. In this paper, we will present the simulation results for the β(v/c) = 0.085 Quarter Wave Resonator (QWR) for the FRIB project. Experimental data will also be presented to benchmark with the simulation results.
WEPPC086 Higher Order Modes Damping Analysis for the SPX Deflecting Cavity Cyromodule 2414
  • L. Xiao, Z. Li, C.-K. Ng
    SLAC, Menlo Park, California, USA
  • A. Nassiri, G.J. Waldschmidt, G. Wu
    ANL, Argonne, USA
  • R.A. Rimmer, H. Wang
    JLAB, Newport News, Virginia, USA
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A single-cell superconducting deflecting cavity operating at 2.812 GHz has been proposed and designed for the Short Pulse X-ray (SPX) project for the Advanced Photon Source upgrade. A cryomodule of 4 such cavities will be needed to produce the required 2-MV deflecting voltage. Each deflecting cavity is equipped with one fundamental power coupler (FPC), one lower order mode (LOM) coupler, and two higher order mode (HOM) couplers to achieve the stringent damping requirements for the unwanted modes. The damping of the HOM/LOM modes below the beampipe cutoff has been analyzed in the single cavity geometry and shown to meet the design requirements. The HOMs above beam pipe cutoff in the 4-cavity cyromodule, however, may result in cross coupling which may affect the HOM damping and potentially trapped modes between the cavities which could produce RF heating to the beamline bellows and even be detrimental to the beam. We have evaluated the HOM damping and trapped modes in the 4-cavity cryomodule using the parallel finite element EM code ACE3P developed at SLAC. We will present the results of the cryomodule analysis in this paper.
WEPPC110 3D Simulations of Multipacting in the 56 MHz SRF Cavity 2477
  • Q. Wu, S.A. Belomestnykh
    BNL, Upton, Long Island, New York, USA
  • L. Ge, C. Ko, Z. Li, C.-K. Ng, L. Xiao
    SLAC, Menlo Park, California, USA
  Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The 56 MHz SRF Quarter-Wave Resonator (QWR) is designed for RHIC as a storage cavity to improve the collider performance. 2D multipacting simulation has been done for the cavity alone. Ripples were added to the outer body of the cavity for multipacting suppression based on the simulation findings. During operation, there will be four higher order mode (HOM) couplers and a fundamental power coupler (FPC) inserted through the end ports of the cavity and a fundamental mode damper (FD) inserted through a special port on the outer body. All of these components will be exposed to high RF fields. In this presentation we compare 2D and 3D codes simulation results for multipacting in the cavity. We also report 3D simulation results for multipacting simulation at the couplers.
WEPPC038 Status of the Short-Pulse X-ray Project at the Advanced Photon Source 2292
  • A. Nassiri, N.D. Arnold, T.G. Berenc, M. Borland, B. Brajuskovic, D.J. Bromberek, J. Carwardine, G. Decker, L. Emery, J.D. Fuerst, A.E. Grelick, D. Horan, J. Kaluzny, F. Lenkszus, R.M. Lill, J. Liu, H. Ma, V. Sajaev, T.L. Smith, B.K. Stillwell, G.J. Waldschmidt, G. Wu, B.X. Yang, Y. Yang, A. Zholents
    ANL, Argonne, USA
  • J.M. Byrd, L.R. Doolittle, G. Huang
    LBNL, Berkeley, California, USA
  • G. Cheng, G. Ciovati, P. Dhakal, G.V. Eremeev, J.J. Feingold, R.L. Geng, J. Henry, P. Kneisel, K. Macha, J.D. Mammosser, J. Matalevich, A.D. Palczewski, R.A. Rimmer, H. Wang, K.M. Wilson, M. Wiseman
    JLAB, Newport News, Virginia, USA
  • Z. Li, L. Xiao
    SLAC, Menlo Park, California, USA
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source Upgrade (APS-U) Project at Argonne will include generation of short-pulse x-rays based on Zholents’* deflecting cavity scheme. We have chosen superconducting (SC) cavities in order to have a continuous train of crabbed bunches and flexibility of operating modes. In collaboration with Jefferson Laboratory, we are prototyping and testing a number of single-cell deflecting cavities and associated auxiliary systems with promising initial results. In collaboration with Lawrence Berkeley National Laboratory, we are working to develop state-of-the-art timing, synchronization, and differential rf phase stability systems that are required for SPX. Collaboration with Advanced Computations Department at Stanford Linear Accelerator Center is looking into simulations of complex, multi-cavity geometries with lower- and higher-order modes waveguide dampers using ACE3P. This contribution provides the current R&D status of the SPX project.
* A. Zholents et al., NIM A 425, 385 (1999).
THPPC040 Improved RF Design for an 805 MHz Pillbox Cavity for the US MuCool Program 3371
  • Z. Li, C. Adolphsen, L. Ge
    SLAC, Menlo Park, California, USA
  • D.L. Bowring, D. Li
    LBNL, Berkeley, California, USA
  Funding: Work supported by US DOE under contract number DE-AC02-05CH11231, and DE-AC02-76SF00515.
Normal conducting RF cavities are required to operate at high gradient in the presence of strong magnetic field in muon ionization cooling channels for a Muon Collider. Experimental studies using an 805 MHz pillbox cavity at MTA of Fermilab has shown significant degradation in gradient performance and damage in the regions that are correlated with high RF fields in magnetic field up to 4 Tesla. These effects are believed to be related to the dark current and/or multipacting activities in the presence of external magnetic field. To improve the performance of the cavity, a new RF cavity with significantly lower surface field enhancement was designed, and will be built and tested in the near future. Numerical analyses of multipacting and dark current were performed using the 3D parallel code Track3P for both the original and new improved cavity profiles in order to gain more insight in understanding of the gradient issues under strong external magnetic field. In this paper, we will present the improved RF design and the dark current and multipacting analyses for the 805 MHz cavity.