Author: Adolphsen, C.
Paper Title Page
WEPWA068 Design Concepts for the NGLS Linac 2271
  • A. Ratti, J.M. Byrd, J.N. Corlett, L.R. Doolittle, P. Emma, J. Qiang, M. Venturini, R.P. Wells
    LBNL, Berkeley, California, USA
  • C. Adolphsen, C.D. Nantista
    SLAC, Menlo Park, California, USA
  • D. Arenius, S.V. Benson, D. Douglas, A. Hutton, G. Neil, W. Oren, G.P. Williams
    JLAB, Newport News, Virginia, USA
  • C.M. Ginsburg, R.D. Kephart, T.J. Peterson, A.I. Sukhanov
    Fermilab, Batavia, USA
  The Next Generation Light Source (NGLS) is a design concept for a multibeamline soft x-ray FEL array powered by a ~2.4 GeV CW superconducting linear accelerator, operating with a 1 MHz bunch repetition rate. This paper describes the concepts under development for a linac operating at 1.3 GHZ and based on minimal modifications to the design of ILC cryomodules in order to leverage the extensive R&D that resulted in the ILC design. Due to the different nature of the two applications, particular attention is given here to high loaded Q operation andμphonics control, as well as high reliability and expected up time.  
WEPWO076 Development of Ultra High Gradient and High Q0 Superconducting Radio Frequency Cavities 2474
  • R.L. Geng, W.A. Clemens, J. Follkie, T. Harris, D. Machie, R. Martin, A.D. Palczewski, E. Perry, G. Slack, R.S. Williams
    JLAB, Newport News, Virginia, USA
  • C. Adolphsen, Z. Li
    SLAC, Menlo Park, California, USA
  • J.K. Hao, Y.M. Li, K.X. Liu
    PKU, Beijing, People's Republic of China
  • P. Kushnick
    JLab, Newport News, Virginia, USA
  Funding: Work supported by DOE. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We report on the recent progress at Jefferson Lab in developing ultra high gradient and high Q0 superconducting radio frequency (SRF) cavities for future SRF based machines. A new 1300 MHz 9-cell prototype cavity is being fabricated. This cavity has an optimized shape in terms of the ratio of the peak surface field (both magnetic and electric) to the acceleration gradient, hence the name low surface field (LSF) shape. The goal of the effort is to demonstrate an acceleration gradient of 50 MV/m with Q0 of 1010 at 2 K in a 9-cell SRF cavity. Fine-grain niobium material is used. Conventional forming, machining and electron beam welding method are used for cavity fabrication. New techniques are adopted to ensure repeatable, accurate and inexpensive fabrication of components and the full assembly. The completed cavity is to be first mechanically polished to a mirror-finish, a newly acquired in-house capability at JLab, followed by the proven ILC-style processing recipe established already at JLab. In parallel, new single-cell cavities made from large-grain niobium material are made to further advance the cavity treatment and processing procedures, aiming for the demonstration of an acceleration gradient of 50 MV/m with Q0 of 2·1010 at 2K.
The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
WEPFI073 A Modular Cavity for Muon Ionization Cooling R&D 2860
  • D.L. Bowring, A.J. DeMello, A.R. Lambert, D. Li, S.P. Virostek, M.S. Zisman
    LBNL, Berkeley, California, USA
  • C. Adolphsen, L. Ge, A.A. Haase, K.H. Lee, Z. Li, D.W. Martin
    SLAC, Menlo Park, California, USA
  • D.M. Kaplan
    Illinois Institute of Technology, Chicago, Illinois, USA
  • T.H. Luo, D.J. Summers
    UMiss, University, Mississippi, USA
  • A. Moretti, M.A. Palmer, R.J. Pasquinelli, Y. Torun
    Fermilab, Batavia, USA
  • R.B. Palmer
    BNL, Upton, Long Island, New York, USA
  The Muon Accelerator Program (MAP) collaboration is developing an ionization cooling channel for muon beams. Ionization cooling channel designs call for the operation of high-gradient, normal-conducting RF cavities in multi-Tesla solenoidal magnetic fields. However, strong magnetic fields have been shown to limit the maximum achievable gradient in RF cavities. This gradient limit is characterized by RF breakdown and damage to the cavity surface. To study this issue, we have developed an experimental program based on a modular pillbox cavity operating at 805 MHz. The modular cavity design allows for the evaluation of different cavity materials - such as beryllium - which may ameliorate or circumvent RF breakdown triggers. Modular cavity components may furthermore be prepared with different surface treatments, such as high-temperature baking or chemical polishing. This poster presents the design and experimental status of the modular cavity, as well as future plans for the experimental program.  
WEPFI080 Waveguide Component R&D for the ILC 2881
  • C.D. Nantista, C. Adolphsen, G.B. Bowden, A.A. Haase, B.D. McKee, F.Y. Wang
    SLAC, Menlo Park, California, USA
  Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515.
Several years of effort have gone into refining the design of the International Linear Collider. The direction the design has evolved in response to driving considerations has resulted in a more sophisticated waveguide system for delivering RF power to the cavities. In particular, the desire to eliminate parallel service tunnels along the main linacs led to the proposal of the Klystron Cluster Scheme (KCS)*, involving plumbing the combined power from groups of klystrons down from the surface at several locations in overmoded waveguide. Additionally, to increase superconducting cavity yield, the acceptance criteria were relaxed to encompass a ±20% range in sustainable operating gradient, which must be accommodated by tailoring of the RF power distribution. Designs and prototype testing of some of the novel waveguide components developed to allow these changes are described here.
* Christopher Nantista and Chris Adolphsen, “Klystron Cluster Scheme for ILC High Power RF Distribution,” presented at the 2009 Particle Accel. Conf., Vancouver, B.C., Canada, May 2009.
WEPFI081 High Power Tests of Overmoded Waveguide for the ILC Klystron Cluster Scheme 2884
  • F.Y. Wang, C. Adolphsen, C.D. Nantista
    SLAC, Menlo Park, California, USA
  A Klystron Cluster Scheme has been proposed for the ILC Main Linacs in which the output power of up to thirty, 10 MW, 1.3 GHz klystrons are combined in a single, 0.5 m diameter circular waveguide in a surface building and transported down to and along the accelerator tunnel where it is periodically tapped-off to power strings of cavities. This schemes eliminates the need for a separate linac service tunnel and simplifies the linac electric and cooling distribution systems. Recently, a 40 meter long circular waveguide with a coaxial input coupler and a 90 degree rf bend were assembled and run in a resonant configuration to test the concept. With the pipe pressurized with up to 30 psig of N2 to raise the rf breakdown threshold, it was demonstrated that field levels equal to those for the 300 MW transmission required for ILC could be sustained reliably. We report on these and other test results from this program.