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LANL

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MOPCH178 Tests on MgB2 for Application to SRF Cavities laser, SLAC, target, cryogenics 481
 
  • T. Tajima
    LANL, Los Alamos, New Mexico
  • I.E. Campisi
    ORNL, Oak Ridge, Tennessee
  • A. Canabal-Rey
    NMSU, Las Cruces, New Mexico
  • Y. Iwashita
    Kyoto ICR, Uji, Kyoto
  • B. Moeckly
    STI, Santa Barbara, California
  • C.D. Nantista, S.G. Tantawi
    SLAC, Menlo Park, California
  • H.L. Phillips
    Jefferson Lab, Newport News, Virginia
  • A.S. Romanenko
    Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
  • Y. Zhao
    University of Wollongong, Institute of Superconducting and Electronic Materials, Wollongong
  Magnesium diboride (MgB2) has a transition temperature (Tc) of ~40 K, i.e., about four times higher than niobium (Nb). The studies in the last three years have shown that it could have about one order of magnitude less RF surface resistance (Rs) than Nb and seems much less power dependent compared to high-Tc materials such as YBCO. In this paper we will present results on the dependence of Rs on surface magnetic fields and possibly the critical RF surface magnetic field.  
 
MOPCH179 Design of a New Electropolishing System for SRF Cavities DESY, KEK, TESLA, controls 484
 
  • T. Tajima
    LANL, Los Alamos, New Mexico
  • C. Boffo
    Fermilab, Batavia, Illinois
  • M.P. Kelly
    ANL, Argonne, Illinois
  • J. Mammosser
    Jefferson Lab, Newport News, Virginia
  Electropolishing (EP) is considered the baseline surface treatment for Superconducting RF (SRF) cavities to achieve >35 MV/m accelerating gradient for the International Linear Collider (ILC). Based on the lessons learned at the forerunners such as KEK/Nomura, DESY and JLAB and on the recent studies, we have started a new design of the next EP system that will be installed in the US. This paper presents requirements, specifications, and the detail of the system design as well as the path forward towards the future industrialization.  
 
THESPA01 Before the Big Bang: An Outrageous New Perspective and its Implications for Particle Physics background, radiation, electron, LEFT 2759
 
  • R. Penrose
    Mathematical Institute, Oxford
  The second law of thermodynaics implies that big bang must have been an extraordinarily precisely organized state. What was the geometrical nature of this state? How can we resolve, in any scientific way, the mystery of how such precision came about? In this talk, a novel (and perhaps outrageous) solution is suggested, which involves an examination of what is to be expected of the very remote future of our universe, with its observed accelerated expansion. Some possible observational consequences of the proposal will be indicated, together with some apparent implications for particle physics, some of which are non-standard.  
 
THPCH071 Coupling Impedances of Small Discontinuities for Non-ultrarelativistic Beams impedance, dipole, coupling, vacuum 2949
 
  • S.S. Kurennoy
    LANL, Los Alamos, New Mexico
  The beam coupling impedances of small discontinuities of an accelerator vacuum chamber have been calculated (e.g., * and references therein) for ultrarelativistic beams using Bethe's diffraction theory. Here we extend the results for an arbitrary beam velocity. The vacuum chamber is assumed to have an arbitrary, but fixed, cross section. The longitudinal and transverse coupling impedances are derived in terms of series over cross-section eigenfunctions, while the discontinuity shape enters via its polarizabilities. Simple explicit formulas for the circular and rectangular cross sections are presented. The impedance dependence on the beam velocity exhibits some unusual features. For example, the reactive impedance, which dominates in the ultrarelativistic limit, can vanish at a certain beam velocity, or its magnitude can exceed the ultrarelativistic value many times.

*S. S. Kurennoy et al. Phys. Rev. ·1052 (1995) 4354.