CERN, Geneva
EPFL, Lausanne
IHEP Protvino, Protvino, Moscow Region
The UA9 experiment at the SPS aims at testing bent crystals for usage as collimators with high energy stored proton and heavy ion beams. The experiments will try to establish crystal-based cleaning efficiency with slowly diffusing beam halo. One method for evaluating efficiency relies on Roman Pots and is described elsewhere. An alternative method relies on observing the beam loss signals around the ring. Comparisons of losses escaping from standard collimators and bent crystals will allow determination of cleaning efficiency, equivalent to the definition used for the LHC collimation design. This alternative method is described and simulations with LHC collimation tracking tools for UA9 are discussed. The predicted beam losses along the SPS ring are presented for different orientations and amorphous layer thicknesses of the crystal. The effect of different diffusion speeds for the beam are discussed.
CERN, Geneva
EPFL, Lausanne
IHEP Protvino, Protvino, Moscow Region
Bent crystals are promised to provide a path towards significant improvement of cleaning efficiency for high power collimation systems. In this paper a possible implementation of a crystal-enhanced collimation system is evaluated for the LHC. Simulation studies were performed with the same state-of the art tracking codes as used for the design of the conventional LHC collimation system. The numerical models are described and predictions for the local and global cleaning efficiency with a crystal-based LHC collimation system are presented. Open issues and further work towards a crystal collimation design for the LHC are discussed.
Fermilab, Batavia
CERN, Geneva
IHEP Protvino, Protvino, Moscow Region
INFN-Ferrara, Ferrara
PNPI, Gatchina, Leningrad District
BNL, Upton, Long Island, New York
Università dell'Insubria & INFN Milano Bicocca, Como
Enrico Fermi Institute, University of Chicago, Chicago, Illinois
Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
Bent-crystal channeling is a technique with a potential to increase the beam-halo collimation efficiency at high-energy colliders. First measurements at the Tevatron in 2005 have shown that using a 5-mm silicon crystal to deflect the proton beam halo onto a secondary collimator improves the system performance by reducing the machine impedance, beam losses in the collider detectors and irradiation of the superconducting magnets, all in agreement with simulations. Recent results, obtained with substantially improved goniometer and enhanced beam diagnostics, are reported showing channeling collimation of the ~1-TeV circulating proton beam halo at the Tevatron collider. Comprehensive results of computer modeling are presented which allow further developments of the T-980 experiment towards a robust system compatible with requirements to high-efficient collimation at the Tevatron and LHC hadron colliders.
UNIFE, Ferrara
IHEP Protvino, Protvino, Moscow Region
INFN-PG, Perugia
Università dell'Insubria & INFN Milano Bicocca, Como
INFN-Roma, Roma
INFN/LNL, Legnaro (PD)
PNPI, Gatchina, Leningrad District
JINR, Dubna, Moscow Region
Università di Roma I La Sapienza, Roma
INFN-Ferrara, Ferrara
CERN, Geneva
INFN-Trieste, Trieste
The H8RD22 collaboration has accomplished an extensive study of axial channeling in the external lines of the CERN SPS. For 400 GeV protons, it was recorded deflection by about 90% of the particles by a short crystal, by far exceeding the performance of previous experiments. Axial channeling with 150 GeV negative hadrons was also firmly observed with deflection capability comparable to the case of positive particles. Near-axis effect such as multiple-volume reflections in a single crystal as a result of the superposition of volume reflections by a series of parallel planes sharing the same axis was investigated with 400 GeV protons. Confirmation of theoretical expectation was observed, in particular most of the particles were deflected by about 50 urad, four times the deflection angle imparted by a single volume reflection of most efficient planes. In this case the angular acceptance was sensitively broader than for the case of channeling. In summary, channeling in axial mode and multi-volume reflections were proven to be two mechanisms for manipulation steering of high-energy particle beams, which side most established techniques such as planar channeling and volume reflection.*
*Contribution on behalf of the H8RD22 collaboration.