• A. Mazzolari, E. Bagli, V. Guidi
  INFN-Ferrara, Ferrara
• S. Baricordi, P. Dalpiaz, D. Vincenzi
  UNIFE, Ferrara
• A. Carnera, D. De Salvador
  Univ. degli Studi di Padova, Padova
• G. Della Mea
  INFN/LNL, Legnaro (PD)
• A.M. Taratin
  JINR, Dubna, Moscow Region

Channeling in bent crystals is a technique with high potential to steer charged-particle beams for several applications in accelerators physics. Revisited methods of silicon micromachining techniques allowed one to realize a new generation of crystals. Characterizations using x-ray diffraction, atomic force microscopy, high resolution transmission electron microscopy and ion beam analysis techniques, showed high quality of the crystals. A specifically designed holder allowed to mechanically bend a crystal at given curvature and remove unwanted torsion. Characterization of such crystals with 400 GeV at CERN H8 external line highlighted 85% single-pass efficiency. A selected crystal has been installed inside the SPS ring in the environment of the CERN experiment UA9 and successfully employed for collimation of the circulating beam.

On behalf of UA9 collaboration

• V. Guidi, E. Bagli, A. Mazzolari
  INFN-Ferrara, Ferrara
• A.G. Afonin, Y.A. Chesnokov, V.A. Maisheev, I.A. Yazynin
  IHEP Protvino, Protvino, Moscow Region
• S. Baricordi, P. Dalpiaz, M. Fiorini, D. Vincenzi
  UNIFE, Ferrara
• D. Bolognini, S. Hasan, M. Prest
  Università dell'Insubria & INFN Milano Bicocca, Como
• G. Della Mea, R. Milan
  INFN/LNL, Legnaro (PD)
• A.S. Denisov, Yu.A. Gavrikov, Yu.M. Ivanov, L.P. Lapina, L.G. Malyarenko, V. Skorobogatov, V.M. Suvorov, S.A. Vavilov
  PNPI, Gatchina, Leningrad District
• S. Golovatyuk, A.D. Kovalenko, A.M. Taratin
  JINR, Dubna, Moscow Region
• A. Mattera
  INFN MIB, MILANO
• W. Scandale
  CERN, Geneva
• S. Shiraishi
  Enrico Fermi Institute, University of Chicago, Chicago, Illinois
• E. Vallazza
  INFN-Trieste, Trieste
• A. V. Vomiero
  INFM-CNR, Istituto Nazionale di Fisica della Materia - Consiglio Nazionale delle Ricerche, Brescia

New results in coherent interaction of negatively-charged particles with bent crystals showed unprecedentedly and significantly high efficiency to manipulate such beams, in the same way as for positively charged particles. Key feature under experimental attainment was the usage of high-quality suitably thin silicon crystals. We experimentally tested crystals Vs. 150 GeV negative pions at external lines of CERN SPS. We observed planar channeling at full deflection angle 30% high single-pass efficiency and large acceptance (about 20μrad). Moreover in the axial case, we reached more than 90% deflection efficiency and larger acceptance (about 60μrad). We also observed volume reflection in a bent crystal, at more than 70% single-pass efficiency with such a wide acceptance as the bending angle. At last, volume reflection by several planes in a single bent crystal was successfully tested with very high efficiency (about 80%). In summary both channeling and volume reflection modes appear to be useful technique for the manipulation of negatively charged beams, e.g. for collimation in the new generation of high intensity accelerators.

The UA9 collaboration