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Zhelamkov, A. V.

Paper Title Page
TUPLS021 First Observation of Proton Reflection from Bent Crystals 1535
 
  • W. Scandale
    CERN, Geneva
  • V.T. Baranov, V.N. Chepegin, Y.A. Chesnokov
    IHEP Protvino, Protvino, Moscow Region
  • Yu.A. Gavrikov, Yu.M. Ivanov, L. P. Lapina, A.A. Petrunin, A.I. Schetkovsky, V. Skorobogatov, A. V. Zhelamkov
    PNPI, Gatchina, Leningrad District
  • V. Guidi
    UNIFE, Ferrara
  • A. Vomiero
    INFN/LNL, Legnaro, Padova
 
  We recently suggested using short bent crystals as primary collimators in a two-stage cleaning system for hadron colliders, with the aim of providing larger impact parameters in the secondary bulk absorber, through coherent beam-halo deflection*. Tests with crystals a few mm long, performed with 70 GeV proton beams at IEHP in Protvino, showed a channeling efficiency exceeding 85%. We also observed disturbing phenomena such as dechanneling at large impact angle, insufficient bending induced by volume capture inside the crystal, multiple scattering of non-channeled protons and, for the first time, a proton flux reflected by the crystalline planes. Indeed, protons with a tangent path to the curved planes somewhere inside the crystal itself are deflected in the opposite direction with respect to the channeled particles, with an angle almost twice as large as the critical angle. This effect, up to now only predicted by computer simulations**, produces a flux of particles in the wrong direction with respect to the absorber, which may hamper the collimation efficiency if neglected.

*A. Afonin et al. PhysRevLett.87.094802(2001).**A. M. Taratin and S.A.Vorobiev, Phys.Lett. A119(1987)425.