Channeling of high energy particles in bent crystals

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Channeling of high energy particles in bent
crystals Experiments at the CERN SPS
CERN 17 November 2004
Cristina Biino
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Introduction

• During the last decade many experiments have been
  performed at the CERN SPS to investigate the use
  of high energy channeled particles in bent
  crystals for extraction, beam splitting and beam
  bending. I discuss the main results obtained by
  the Aarhus-CERN-Strasbourg etc collaboration.
• See NIM B 164-165 (2000) 27-43
• and references within.

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Model for deflection efficiency
Essentially the optimum length in units of the
dechanneling length and the maximum efficiency is
fixed by the choice of the angle for a wide range
of energies.
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Comparison model vs experiment

• One of the early experiments at CERN confirmed
  expectations on the behaviour of the efficiency
  as a function of the angle for a 450 GeV/c proton
  beam in a bent Si (111) crystal

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High Z crystals

• The equivalent field of a bent crystal increases
  proportionally with Z
• while the dechanneling length does not depend on
  Z. Thus one may
• expect to obtain higher efficiencies from a heavy
  crystal.

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Highly Charged Ions

• Since the critical angle, the
• critical curvature, multiple
• Coulomb Scattering and
• thus the dechanneling
• length only depend on the
• Ratio of projectile charge
• to momentum, one may
• expect that ions with the
• same momentum per charge
• as protons are deflected in
• a crystal with similar
• efficiencyes.

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Extraction

• At the CERN SPS a series of experiments have
  proven the
• existence of the multi pass extraction mechanism,
  investigated
• the energy dependence at 14, 120 and 270 GeV and
  have
• managed to extract 22 TeV Pb 82 ions.

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Beam splitting in the K12 beam for NA48