Problems with Radial Electric Field

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Hi,

I designed a class derived from G4ElectricField to setup a non-uniform, radial electric field inside a cylindrical He3 Tube (E = Voltage / ( radius * ln(b/a)), where Voltage, b, and a are 3 parameters and r is the radius at which the field is evaluated and contains the position dependence).

I am attaching the relevant files (4 of them). In addition, I have the following few lines in myDetDetectorConstruction:

#include "myDetFieldSetup.hh"

logicGasTube = new G4LogicalVolume(solidGasTube , gasmixture, "gastube_log");

  // Set local field manager and local Electric Field in he3 tube
  G4bool allLocal = true ;

  logicGasTube->SetFieldManager( fEmFieldSetup->GetLocalFieldManager(), 
                                  allLocal ) ;

The code compiles fine, but I am getting the following error as I throw a thermal neutron at my tube:

Start Run processing.
  G4ParticleChange::CheckIt    : the global time goes back  !!
  Difference:  11577.237025344[ns] 
  G4ParticleChange::CheckIt    : the proper time goes back  !!
  Difference:  11576.449246183[ns] 
 G4ParticleChange::CheckIt 
      -----------------------------------------------
        G4ParticleChange Information  
      -----------------------------------------------
        # of 2ndaries       :                    0
      -----------------------------------------------
        Energy Deposit (MeV):                    0
        Non-ionizing Energy Deposit (MeV):                    0
        Track Status        :                Alive
        True Path Length (mm) :                  0.8
        Stepping Control      :                    0
        Mass (GeV)   :                    0
        Charge (eplus)   :                    0
        MagneticMoment   :                    0
                :  =                    0*[e hbar]/[2 m]
        Position - x (mm)   :                 14.2
        Position - y (mm)   :                 20.8
        Position - z (mm)   :                -4.77
        Time (ns)           :                    0
        Proper Time (ns)    :            -1.16e+04
        Momentum Direct - x :                0.493
        Momentum Direct - y :               -0.863
        Momentum Direct - z :               -0.115
        Kinetic Energy (MeV):                0.191
        Polarization - x    :                    0
        Polarization - y    :                    0
        Polarization - z    :                    0
        Touchable (pointer) :            0xab1b008

*** G4Exception : 200
      issued by : G4ParticleChange::CheckIt
momentum, energy, and/or time was illegal
*** Event Must Be Aborted 
Run terminated.

I would appreciate your input in what I may be doing wrong here.

Thank you,

Clarisse

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2009/04/27/07.35-23670-nclude_myDetFieldSetup.hh
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2009/04/27/07.35-32084-DetRadialElectricField.hh
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2009/04/27/07.35-88341-3_src_myDetFieldSetup.cxx
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2009/04/27/07.35-98902-etRadialElectricField.cxx