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Geant4/examples/extended/field/field05/README

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  1 
  2      =========================================================
  3      Geant4 - an Object-Oriented Toolkit for Simulation in HEP
  4      =========================================================
  5 
  6 
  7 
  8                             field05 Example
  9                             ---------------
 10 
 11      This example checks so-called "spin-frozen" condition
 12      There is a good example article hep-ph/0012087v1.
 13      This article discusses about how to cancel the muon g-2 precession by
 14      applying an electric field.
 15 
 16      1) beta is muon velocity,
 17      2) B is an uniform magnetic field and \vec{beta}.\vec{B}=0,
 18         "." means scalar product,
 19      3) Radial electric field (E) in the lab frame and \vec{beta}.\vec{E}=0,
 20      4) a=(g-2)/2 is muon anomalous magnetic moment.
 21 
 22      The required electric field to cancel the g-2 precession is,
 23      E=a*B*light_c*gamma**2*beta.
 24 
 25      In case of gamma=5 and B=0.24 Tesla, the required electric field is
 26      E=2 MV/m.
 27 
 28      "Spin-frozen" happens when spin rotation cycle and muon rotation cycle
 29      are same. In this case, both cycles should be 149.5 nsec.
 30 
 31      See also:
 32      http://research.kek.jp/people/hiromi/MyHomePage/G-2_work_files/SpinStudyinEMfieldByGeant4.pdf
 33 
 34 
 35      Credit goes to Hiromi Iinuma from KEK.
 36 
 37 **************
 38 *Classes Used*
 39 **************
 40 
 41  1 - main()
 42 
 43     See field05.cc.
 44 
 45  2- GEOMETRY DEFINITION
 46 
 47     as simple world G4Box with a G4ElectroMagneticField
 48     propagating both spin and momentum (G4EqEMFieldWithSpin)
 49     with G4ClassicalRK4(fEquation,12) and
 50     Bz = 0.24*tesla;
 51     Er = 2.113987E+6*volt/m;
 52 
 53  3- AN EVENT: THE PRIMARY GENERATOR
 54 
 55     use mu+ G4ParticleGun with Pmu = 517.6*MeV/c
 56     and aligned spin and momentum direction
 57 
 58  4- PHYSICS
 59 
 60     RegisterPhysics(new G4SpinDecayPhysics());
 61     RegisterPhysics(new G4StepLimiterPhysics());
 62 
 63     G4SpinDecayPhysics defines muon decay modes with spin,
 64     G4StepLimiterPhysics defines G4StepLimiter and G4UserSpecialCuts.
 65 
 66  5- User Action Classes
 67 
 68         SteppingAction:
 69             G4Exception when the cosine of the angle between
 70             the spin and the momentum is < (1.-1.E-7)
 71 
 72  6- HOW TO START ?
 73 
 74         - Execute field05 in 'batch' mode from macro files e.g.
 75                 % field05 field05.in > field.out &
 76 
 77         - Execute field05 in 'interactive' mode with visualization e.g.
 78                 % field05
 79                 ....
 80                 Idle> type your commands, for example:
 81                 Idle> run/beamOn 1
 82                 ....