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Spickermann, T.

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MOPAS081 Spallation Neutron Source (SNS) Diamond Stripper Foil Development 620
  • R. W. Shaw, M. A. Plum, L. L. Wilson
    ORNL, Oak Ridge, Tennessee
  • M. J. Borden, T. Spickermann
    LANL, Los Alamos, New Mexico
  • C. S. Feigerle
    University of Tennessee, Knoxville, Tennessee
  • Y. Irie
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • I. Sugai, A. Takagi
    KEK, Ibaraki
  Funding: SNS is managed by UT-Battelle, LLC, for the U. S. DOE under contract DE-AC05-00OR22725. DOE contract W-7405-ENG-36 (LANL) and Japan SPS contract 18540303 (KEK) supported work at those institutions.

Diamond stripping foils are under development for the SNS. Free-standing, flat 350 microgram/cm2 foils as large as 17 x 25 mm have been prepared. These nano-textured polycrystalline foils are grown by microwave plasma-assisted chemical vapor deposition in a corrugated format to maintain their flatness. They are mechanically supported on a single edge by a residual portion of their silicon growth substrate; typical fine foil supporting wires are not required for diamond foils. Six foils were mounted on the SNS foil changer in early 2006 and have performed well in commissioning experiments at reduced operating power. A diamond foil was used during a recent experiment where 12 microCoulombs of protons, approximately 40% of the design value, were stored in the ring. A few diamond foils have been tested at LANSCE/PSR, where one foil was in service for a period of five months (820 Coulombs of integrated injected charge) before it was replaced. Diamond foils have also been tested in Japan at KEK (650 keV H-) where their lifetimes slightly surpassed those of evaporated carbon foils, but fell short of those for Sugai's new hybrid boron carbon (HBC) foils.

TUODAB02 Electron Cloud Generation and Trapping in a Quadrupole Magnet at the LANL PSR 828
  • R. J. Macek, J. E. Ledford, R. J. Macek
    TechSource, Santa Fe, New Mexico
  • M. J. Borden, A. A. Browman, R. C. McCrady, J. F. O'Hara, L. Rybarcyk, T. Spickermann, T. Zaugg
    LANL, Los Alamos, New Mexico
  • M. T.F. Pivi
    SLAC, Menlo Park, California
  Funding: Work supported by DOE SBIR Grant No. DE-FG02-04ER84105 and CRADA No. LA05C10535 between TechSource, Inc. and the Los Alamos National Laboratory.

Recent beam physics studies on the two-stream e-p instability at LANL proton storage ring (PSR) have focused on the role of the electron cloud generated in quadrupole magnets where electrons, which seed beam-induced multipacting, are expected to be largest due to grazing angle losses from the beam halo. A new diagnostic to measure electron cloud formation and trapping in a quadrupole magnet has been developed, installed, and successfully tested at PSR. Experimental results will be presented on various characteristics of electron cloud obtain from experiments using this diagnostic and compared with simulations. Results include data on flux and energy spectra of electrons striking the vacuum chamber, the line density and lifetime of electrons trapped in the quadrupole after the beam has been extracted as well as evidence regarding electrons ejected from the magnet during passage of the proton beam.

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