Author: Hirshfield, J.L.
Paper Title Page
MOP107 Status of Dielectric-Lined Two-Channel Rectangular High Transformer Ratio Accelerator Structure Experiment 298
 
  • S.V. Shchelkunov, M.A. LaPointe
    Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
  • M.E. Conde, W. Gai, J.G. Power, Z.M. Yusof
    ANL, Argonne, USA
  • J.L. Hirshfield
    Omega-P, Inc., New Haven, Connecticut, USA
  • T.C. Marshall
    Columbia University, New York, USA
  • D. Mihalcea
    Northern Illinois University, DeKalb, Illinois, USA
  • G.V. Sotnikov
    NSC/KIPT, Kharkov, Ukraine
 
  Funding: This work is supported by DoE, Office of High Energy Physics
Recent tests of a two-channel rectangular dielectric lined accelerator structure are described; comparison with theory and related issues are presented. The structure (with channel width ratio 6:1) is designed to have a maximum transformer ratio of ~12.5:1. It operates mainly in the LSM31 mode (~ 30GHz). The dielectric liner is cordierite (dielectric constant ~4.76). The acceleration gradient is 1.2 MV/m for each 10nC of the drive bunch for the first acceleration peak of the wakefield, and 0.92 MV/m for the second peak. The structure is installed into the AWA beam-line (Argonne National Lab) and is excited by a single 10-50nC, 14MeV drive bunch. Both the drive bunch and a delayed witness bunch are produced at the same photocathode. This is the first experiment to test a two-channel dielectric rectangular wakefield device where the accelerated bunch may be continuously energized by the drive bunch. The immediate experimental objective is to observe the energy gain and spread, and thereby draw conclusions from the experimental results and the theory model predictions. The observed energy change of the test bunch might be well explained*.
* G. V. Sotnikov, et al., Advanced Accelerator Concepts: 13th Workshop, Carl B. Schroeder, Wim Leemans and Eric Esarey, editors, AIP Conf. Proc. 1086), pp. 415–420 (AIP, New York, 2009).
 
 
MOP112 Study of Enhanced Transformer Ratio in a Coaxial Dielectric Wakefield Accelerator using a Profiled Drive Bunch Train 304
 
  • G.V. Sotnikov
    NSC/KIPT, Kharkov, Ukraine
  • J.L. Hirshfield
    Yale University, Physics Department, New Haven, CT, USA
  • T.C. Marshall, G.V. Sotnikov
    Omega-P, Inc., New Haven, Connecticut, USA
 
  Funding: The research was supported by US Department of Energy, Office of High Energy Physics, Advanced Accelerator R & D.
A key parameter of wakefield acceleration is the transformer ratio T. For a dielectric wakefield accelerator, it has been suggested to use a ramped drive bunch train (RBT), or a multizone dielectric structure to enhance T. Here we show the possibility of greatly improving the RBT technique by the use of a numerical algorithm. We study a two-channel 28 GHz structure with two nested Alumina cylindrical shells (CDWA) which is to be excited by a train of four annular bunches having energy 14 MeV and axial RMS size 1mm; the total charge of bunches is 200 nC. For bunch charge and spacing chosen for optimum acceleration gradient, or for optimizing T using the standard method, we obtain T~3.6. We found that if the charge ratios are 1.0:2.4:3.5:5.0 and the spaces between the bunches are 2.5, 2.5, and 4.5 wakefield periods, then T~17. The RBT also can be used successfully in a high gradient THz CDWA structure.
* C.Jing et.al., Phys. Rev. Lett. 98 144801, (2007)
** C. Wang, et.al. Proc. PAC 2005. IEEE, 2005, p.1333.
*** G. Sotnikov et.al. PRST-AB, 061302 (2009).
 
 
MOP144 Multi-Harmonic Cavity for RF Breakdown Studies 361
 
  • Y. Jiang
    Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
  • J.L. Hirshfield
    Yale University, Physics Department, New Haven, CT, USA
  • S. Kazakov, S.V. Kuzikov
    Omega-P, Inc., New Haven, Connecticut, USA
 
  Funding: DOE, Office of HEP
An axially-asymmetric cavity to support several modes at harmonically-related frequencies is predicted to sustain higher RF breakdown thresholds than a conventional pillbox cavity, when driven by two or more external RF phase-locked harmonic sources. Experimental efforts are underway at Yale Beam Physics Lab to study RF breakdown in a bimodal asymmetric cavity. Such a cavity could be a basic building-block for a future high-gradient warm accelerator structure.
* S.Yu. Kazakov, S.V. Kuzikov, Y. Jiang, and J.L. Hirshfield, PRSTAB, 13, 071303 (2010).
** S.V. Kuzikov, S.Yu. Kazakov, Y. Jiang, and J.L. Hirshfield, PRL 104, 214801 (2010).
 
 
TUP073 Development of an L-band Ferroelectric Phase Shifter 955
 
  • S. Kazakov, N. Solyak, V.P. Yakovlev
    Fermilab, Batavia, USA
  • J.L. Hirshfield
    Yale University, Physics Department, New Haven, CT, USA
  • A. Kanareykin, E. Nenasheva
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S.V. Shchelkunov
    Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
 
  Effective operation of the RF cavities in the superconducting accelerators demands fast, high-power RF vector modulators. Recent progress in development of the new materials, ferroelectrics, having tunable dielectric constant and acceptable losses [*] gives the possibility development of such devises. In previous papers [**-***] the authors described different L-band ferroelectric phase shifter designs . At low RF level high operation speed of 2 degree/nsec was demonstrated in waveguide phase shifter. However, the experiments show that a special technology is to be developed that provides a good electric contact between ceramics and the metallic wall. In present paper a new design of the fast high–power ferroelectric phase shifter is described based on the simple ferroelectric elements.
* A. Kanareykin, et al, IPAC 2010, p. 3987
** S. Kazakov, et al, “Fast Ferroelectric Phase Shifter Design For ERLs,” 45th ICFA Beam Dynamics Workshop, 2009
*** S. Kazakov, et al, PAC2007, p. 599.