INFN-Roma, Roma
CERN, Geneva
JINR, Dubna, Moscow Region
We present a detailed analysis of the beam loss data collected at the SPS during the 2009 machine developments devoted to test crystal collimation. Scintillator counters and Gas electron multiplier detectors were installed in special points to detect the effect of inelastic interaction of protons with the crystals in various orientation with respect to the beam. Clear correlations of the counting rates with the crystal positions and orientation were detected during the data-taking and were crucial to put the crystal in optimal channeling position. For one of the crystal the pattern of losses showed evidence of several planar and axial channeling conditions.
Fermilab, Batavia
CERN, Geneva
IHEP Protvino, Protvino, Moscow Region
INFN-Ferrara, Ferrara
PNPI, Gatchina, Leningrad District
BNL, Upton, Long Island, New York
The T980 crystal collimation experiment is underway at the Tevatron to study various crystal types and parameters and evaluate if this technique would increase TeV beam-halo collimation efficiency at high-energy hadron colliders such as the Tevatron and the LHC. The setup has been substantially enhanced during the Summer 2009 shutdown by installing a new O-shaped crystal in the horizontal goniometer, adding a vertical goniometer with two alternating crystals (O-shaped and multi-strip) and additional beam diagnostics. First measurements with the new system are quite encouraging, with channeled and volume-reflected beams observed on the secondary collimators as predicted. Investigation of crystal collimation efficiencies with crystals in volume reflection and channeling modes are described in comparison with an amorphous primary collimator. Results on the system performance are presented for the end-of-store studies and for entire collider stores. Planning is underway for dedicated studies during a Tevatron post-collider physics running period.
CERN, Geneva
INFN-Roma, Roma
The UA9 experiment was performed in 6 MDs from May to November 2009 with the goal of studying the collimation properties of a crystal in the framework of a future exploitation in the LHC collimation system. An important parameter evaluated for the characterization of the crystal collimation is the efficiency of halo extraction when the crystal is in channeling mode. In this paper it is explained how this efficiency can be measured using a pixel detector, the Medipix, installed in the Roman Pot of UA9. The number of extracted particles counted by the Medipix is compared with the total number of circulating particles measured by the Beam Current Transformers (BCTs): from this comparison the efficiency of the system composed by the crystal, used in channeling mode, and a tungsten absorber is proved to be greater than 85%.
CERN, Geneva
JINR, Dubna, Moscow Region
A number of tests were performed by the UA9 Collaboration* in the North area of the SPS in view of investigating crystal-particles interactions for future application in hadron colliders. The rate of nuclear reactions was measured with 400 GeV proton beams directed into a silicon bent crystal. In this way the background induced by the crystal itself either in amorphous or in channeling orientation was revealed. The results provide fundamental information to put in perspective the use of silicon crystals to assist halo collimation in hadron colliders, whilst minimizing the induced loss. Crystals made of Germanium were also investigated in view of the expected increase of the collimation efficiency respect to silicon. Finally, crystals were tested in axial orientation and with incoming particles of negative charge. The collected results are presented in details.
* http://greybook.cern.ch/programmes/experiments/UA9.html
INFN-Ferrara, Ferrara
IHEP Protvino, Protvino, Moscow Region
UNIFE, Ferrara
Università dell'Insubria & INFN Milano Bicocca, Como
INFN/LNL, Legnaro (PD)
PNPI, Gatchina, Leningrad District
JINR, Dubna, Moscow Region
INFN MIB, MILANO
CERN, Geneva
Enrico Fermi Institute, University of Chicago, Chicago, Illinois
INFN-Trieste, Trieste
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