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Forum: Fields: Magnetic and Otherwise
Re: Sad the proper time goes back (Olivier Dadoun)
Re: Ok Re: the proper time goes back (Olivier Dadoun)
Re: Warning Re: the proper time goes back (Gumplinger Peter)
Date: 03 Apr, 2012
From: Anushree Ghosh <Anushree Ghosh>

Hii,
  I am using Geant4.9.po2 and at the time of running my program, I am getting the following message for some events:

  G4ParticleChange::CheckIt    : the global time goes back  !!
  Difference:  10.343230216315[ns] 
  G4ParticleChange::CheckIt    : the proper time goes back  !!
  Difference:  10.339190245742[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
        Stepping Control      :                    0
        Mass (GeV)   :                    0
        Charge (eplus)   :                    0
        MagneticMoment   :                    0
                :  =                    0*[e hbar]/[2 m]
        Position - x (mm)   :             1.79e+03
        Position - y (mm)   :             1.34e+03
        Position - z (mm)   :             2.54e+03
        Time (ns)           :                 19.2
        Proper Time (ns)    :                -10.2
        Momentum Direct - x :              0.00313
        Momentum Direct - y :               -0.446
        Momentum Direct - z :               -0.895
        Kinetic Energy (MeV):                 1.46
        Polarization - x    :                    0
        Polarization - y    :                    0
        Polarization - z    :                    0
        Touchable (pointer) :            0x1b6b8a8

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

I have defined  magnetic filed inside my code.
However this problem is not there for Geant4.9.3.po2 and for other older versions.
I have followed the method mentioned in the previous mail but I could not resolve it. 
 Can anyone tell me how to get rid off it?
Thanks in advance.

On Fri, 18 Sep 2009 02:45:17 GMT, Gumplinger Peter wrote:

> Dear Oliver,
> 
> > I have followed the recommendation gave by
> 
> > Peter Gumplinger http://tinyurl.com/nfpk7t
> 
> Thanks for bringing this to my/users' attention. The code in the above
> forum link is still not entierly correct; it would be for a localized
> pure magnetic field but for EM-fields we need:
> 
>    G4int nvar = 8;  // To integrate time & energy 
>                     //    in addition to position, momentum
> 
> and the correct code for EM-fields should read:
> 
>     G4int nvar = 8;
>     fStepper = new G4ClassicalRK4( fEquation, nvar );
> 
> for the default in the G4ClassicalRK4 constructor is nvar=6 and hence
> tailored to pure mag. fields.
> 
> you can then subsequently use:
> 
>     fIntgrDriver = new G4MagInt_Driver(fMinStep, 
>                                      fStepper, 
>                                      fStepper->GetNumberOfVariables() );
> 
> This should be the right approach rather than just:
> 
>     fIntgrDriver = new G4MagInt_Driver(fMinStep, 
>                                      fStepper, 
>                                      8);
> 
> Please, also see the code fragment (Example 4.12) in the Application
> Developers Guide:
> 
> http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/ForApplicationDeveloper/html/ch04s03.html#sect.EMField.Pract
> 
> Regards, Peter
> 

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