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Comparative results on collimation of the SPS beam of protons and Pb ions with bent crystals |
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| Affiliation: | a CERN, European Organization for Nuclear Research, CH-1211 Geneva 23, Switzerland b Laboratoire de l?Accelerateur Lineaire (LAL), Universite Paris Sud Orsay, Orsay, France c INFN Sezione di Ferrara, Dipartimento di Fisica, Universitá di Ferrara, Ferrara, Italy d INFN LNF, Via E. Fermi, 40 00044 Frascati, Rome, Italy e INFN Laboratori Nazionali di Legnaro, Viale Universitá 2, 35020 Legnaro (PD), Italy f INFN Sezione di Roma, Piazzale Aldo Moro 2, 00185 Rome, Italy g INFN Sezione di Napoli, Italy h Institute of High Energy Physics, Moscow Region, 142284 Protvino, Russia i Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region, Russia j Petersburg Nuclear Physics Institute, 188300 Gatchina, Leningrad Region, Russia k Imperial College, London, United Kingdom l Brookhaven National Laboratories, P.O. Box 5000, Upton, NY 11973-5000, USA m SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA |
| Abstract: | New experiments on crystal assisted collimation have been carried out at the CERN SPS with stored beams of 120 GeV/c protons and Pb ions. Bent silicon crystals of 2 mm long with about 170 μrad bend angle and a small residual torsion were used as primary collimators. In channeling conditions, the beam loss rate induced by inelastic interactions of particles with the crystal nuclei is minimal. The loss reduction was about 6 for protons and about 3 for Pb ions. Lower reduction value for Pb ions can be explained by their considerably larger ionization losses in the crystal. In one of the crystals, the measured fraction of the Pb ion beam halo deflected in channeling conditions was 74%, a value very close to that for protons. The intensity of the off-momentum halo leaking out from the collimation station was measured in the first high dispersion area downstream. The particle population in the shadow of the secondary collimator-absorber was considerably smaller in channeling conditions than for amorphous orientations of the crystal. The corresponding reduction was in the range of 2-5 for both protons and Pb ions. |
| Keywords: | Accelerator Beam collimation Crystal Channeling |
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