Gabriele Cosmo
72 lines
2.8 KiB
Plaintext
72 lines
2.8 KiB
Plaintext
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Channeling effect in Geant4
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Enrico Bagli - INFN and University Ferrara (Italy)
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bagli@fe.infn.it
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This example shows how channeling in bent crystal can be simulated
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in Geant4
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1.INTRODUCTION
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The example simulates the channeling of 400 GeV/c protons in bent
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Si crystal. Channeling occurs when particles enter a crystal aligned
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with atomic planes or axes. In bent crystals, the particles are
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trapped between atomic planes and follow the crystal curvature
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being deflected. If the particle direction is tangent to a bent
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crystal plane is reflected to the opposite direction with respect
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to channeling, i.e., it suffer ‘volume reflection’. The example
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provides the physical model for planar channeling and volume
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reflection in bent crystals.
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2.GEOMETRY
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The geometry is a bent Si crystal with three Si detectors placed at
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-9.998 m, -0.320 m and 10.756 m with respect to the position of
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the bent crystal itself. The Si detectors allows to measure
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incoming and outgoing angle after the interaction with the Si bent crystal.
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The geometry is all under vacuum.
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3.PRIMARY EVENT
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The primary events are 400 GeV/c protons launched at -10.5 m from the
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crystal with 13.36 microrad x 11.25 microrad divergence.
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4.PHYSICS
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In the example the physics of channeling and volume reflection
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has been added to the standard Geant4 physics. The description
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of the used model can be found in the paper ‘A model for the
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interaction of high-energy particles in straight and bent
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crystals implemented in Geant4’ by E. Bagli et al., available
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online at http://arxiv.org/abs/1403.5819
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5.EXECUTION & OUTPUT
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The executable must be run from within the source directory of the example
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to ensure that it can find the path for crystal data files.
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Data files for Si crystal interplanar potential, nuclei and electron density
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are stored in a subdirectory named ’data’
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Upon execution, the 2009_PLB680_129.mac macro will automatically run the
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example with 1000 protons.
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Use
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/xtal/setBR XXX 0. 0. m
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To change crystal bending to XXX meters
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Use
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/xtal/setSize 1.0 70. XXX mm
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To change crystal length to XXX millimeter
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Use
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/xtal/potfilename data/Si220pl
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To select the (110) Si crystal plane of channeling
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GPS commands are used for the primary generator.
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The output is the ExExhCh.root file with the TTree ExExChTree
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has the leaves:
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- angXin : incoming particle X angle at the crystal
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- angYin : incoming particle Y angle at the crystal
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- posXin : hitting X position of the particle at the crystal
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- posYin : hitting Y position of the particle at the crystal
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- angXout: outgoing particle X angle out of the the crystal
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- angYout: outgoing particle Y angle out of the the crystal
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