Keyword: higher-order-mode
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THPAK017 Higher Order Modes in China-ADS Demo Linac dipole, HOM, cavity, linac 3240
 
  • C. Zhang, Y. He, T.C. Jiang, R.X. Wang, S.H. Zhang
    IMP/CAS, Lanzhou, People's Republic of China
 
  Funding: Work supported by Natural Science Foundation of China,No.11505253
The study of higher order modes excited in the China-ADS Linac has been presented in this paper. The effects of the cryogenic losses and the influence on beam of the higher order modes have been investigated.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK017  
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THPAK113 Cavity Characterization Studies With the Latest Revision of YACS cavity, storage-ring, coupling, superconducting-cavity 3503
 
  • B.D. Isbarn, S. Koetter, B. Riemann, M. Sommer, T. Weis
    DELTA, Dortmund, Germany
 
  Funding: Work supported by the BMBF under contract no. 05K13PEB.
YACS is a 2.5D finite element method solver capable of solving for the full 3D eigenfrequency spectra of resonant axisymmetric structures while reducing the computational problem to a 2D rotation plane. The most recent revision of YACS now supports arbitrary order basis functions for the geometry and field discretization. In earlier revisions of YACS spurious modes were introduced by increasing the order of either the geometry or field basis functions. To prevent the emergence of spurious modes, YACS now matches the function spaces of the in-plane and out-plane function basis, and thus yields spurious free solutions. To demonstrate the capabilities of YACS, extensive cavity characterization studies on curved multicell microwave cavities are presented. Due to the combined utilization of the rotation symmetry, higher order basis functions and curved elements, eigenfrequency spectra above 10 GHz for L-band multicell structures can be easily obtained.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK113  
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THPML012 Simulations and Measurements of the Wakefield Loading Effect in Argonne Wakefield Accelerator Beamline wakefield, experiment, linac, acceleration 4675
 
  • J. Upadhyay, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
  • M.E. Conde, Q. Gao, N.R. Neveu, J.G. Power, J.H. Shao, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • N.R. Neveu
    IIT, Chicago, Illinois, USA
 
  A beam driven acceleration experiment in a photonic band gap (PBG) structure is planned at Argonne wakefied accelerator (AWA) facility at Argonne National Laboratory. We plan to pass a high charge (drive) beam through a travelling wave 11.7 GHz PBG structure and generate a wakefield. This wakefield will be probed by a low charge (witness) beam to demonstrate wakefield acceleration and deceleration. The drive and witness bunches will be accelerated to above 60 MeV in the main accelerator at AWA which has frequency of 1.3 GHz. The charges used in this experiment could be as high as 20 nC. To measure the exclusive effect of PBG the structure on acceleration and deceleration of the witness bunch we have to exclude the effect of beam loading of the main AWA accelerator structure. To understand the wakefield effect in AWA, we conducted an experiment where we passed the high charge (10 nC) beam through the accelerator structure which was followed by a 2 nC witness beam separated by 4 wavelength. The energy of witness beam was measured in the presence and absence of the drive beam. The beam loading was observed and quantified. The results of this work will be presented in the conference.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML012  
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THPML013 Demonstration of the Wakefield Acceleration in an 11.7 GHz Photonic Band Gap Accelerator Structure experiment, wakefield, acceleration, electron 4678
 
  • J. Upadhyay, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
  • M.E. Conde, Q. Gao, N.R. Neveu, J.G. Power, J.H. Shao, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
 
  We plan to conduct a beam driven acceleration experiment in a photonic band gap (PBG) accelerator structure operating at 11.7 GHz at Argonne Wakefield Accelerator (AWA) facility. For the experiment, the PBG structure will be excited by a high charge (up to 10 nC) electron bunch, and a second smaller charge witness bunch will be accelerated. Because the PBG structure was fabricated with electroforming, the AWA beamline includes a Be window placed before the PBG structure that protects the cathode from contamination due to possible outgassing from the electroformed copper. The diameter of the Be window is 9 mm and the beam tube diameter of the PBG structure is 6.4 mm. The size of the high charge electron beam on Be window has to be minimized to minimize scattering. The parameters of the beamline had to be adjusted to achieve good propagation of the beam. An OPAL simulation for the AWA beamline was performed for 1, 5, and 10 nC beams. The beam size was experimentally measured at different positions in the beamline for different charges to verify simulations. Finally, the high charge electron beam was passed through the PBG structure and acceleration of the witness bunch was measured  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML013  
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THPML125 Efficiency Analysis of High Average Power Linacs for Environmental and Industrial Applications linac, impedance, beam-loading, coupling 4970
 
  • M. Shumail, V.A. Dolgashev
    SLAC, Menlo Park, California, USA
 
  Funding: U.S. Department of Energy, HEP under Research Opportunities in Accelerator Stewardship: LAB 16-1438.
We present comprehensive efficiency equations and useful scaling laws to optimally determine design parameters for high efficiency rf linacs. For the first time we have incorporated the parasitic losses due to the higher order cavity modes into the efficiency analysis of the standing wave (SW) and travelling wave (TW) accelerators. We have also derived the efficiency equations for a new kind of attenuation-independent-impedance travelling wave (ATW) accelerators where the shunt impedance can be optimized independent of the group velocity. We have obtained scaling laws which relate the rf to beam efficiency to the linac length, beam aperture radius , phase advance per cell, and the type of accelerating structure: SW versus TW, disk-loaded (DL) versus nose-cone (NC). We give an example of using these scaling laws to determine a feasible set of parameters for a 10 MeV, 10 MW linac with 97.2% efficiency.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML125  
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