Abstracts Brochure - CERN

TUPLS — Poster Session 27-Jun-06 16:00 - 18:00
First Observation of Proton Reflection from Bent Crystals
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
W. Scandale (CERN) V. Baranov, V.N. Chepegin, Y.A. Chesnokov
(IHEP Protvino) Yu.A. Gavrikov, Yu.M. Ivanov, L. P. Lapina, A.A.
Petrunin, A.I. Schetkovsky, V. Skorobogatov, A. V. Zhelamkov
(PNPI) V. Guidi (UNIFE) A. Vomiero (INFN/LNL)
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.
Experimental Study of Crystal Channeling at CERN-SPS for Beam-halo Cleaning
An efficient and robust collimation system is
mandatory for any superconducting hadron
collider, in particular for the LHC, which will
store a beam of unprecedented high intensity
and energy. The usage of highly efficient and
short primary bent-crystal collimators might
M. Fiorini, V. Guidi (UNIFE) R.W. Assmann, C. Biino, I.
Efthymiopoulos, L. Gatignon, W. Scandale (CERN) Y.A. Chesnokov
(IHEP Protvino) Yu.M. Ivanov (PNPI) N.V. Mokhov (Fermilab) S.
Stefano (INFN-Pisa) A.M. Taratin (JINR) A. Vomiero (INFN/LNL)
be a possibility for reaching nominal and ultimate LHC intensity. Over the last years, groups in Russia (St. Petersburg)
and Italy (Ferrara) have developed crystal production methods, which considerably improve the crystal quality. In
view of the crystal-collimation experiments at the Tevatron and of the potential improvement compared with the
phas·10 -1 LHC collimation system, considering the recent progress in crystal technology, we proposed experiments
for crystal characterization in the SPS beam lines. Major objectives will be: 1) qualification of the new crystals to be
used in the Tevatron; 2) measuring the channeling efficiency of long crystals with 1 mrad and/or 8 mrad bending
angle; and 3) comparison of loss patterns around the ring for a crystal with one for amorphous material. In this paper
we will report the progress towards the SPS experiment.
A Project To Construct the First Non-Scaling FFAGs in the UK
Non-scaling FFAGs were originally invented
in 2002 for muon acceleration at a Neutrino T.R. Edgecock (CCLRC/RAL)
Factory. Their non-scaling nature allows the
particle orbits to be compressed, with the result that the orbit excursion can be much smaller than in a scaling FFAG,
by up to a factor of 10. This should bring a considerable cost saving, but with similar performance. Interest has now
spread to using them for accelerating protons and for hadron therapy. Studies have indicated that their properties
mean that they would have significant advantages for these applications over current technology. However, nonscaling
FFAGs have a number of unique features compared to most existing accelerator types, in particular multiple
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