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Question Re: Electrons not affected by electric field? 

Forum: Fields: Magnetic and Otherwise
Re: None Electrons not affected by electric field? (Robert Schaefer)
Date: 19 Jan, 2015
From: Robert Schaefer <Robert Schaefer>

Dear John,

thanks for your quick reply. I've implemented your remarks. Now sometimes I get the following messages:

1)//----------------------------------------------------------------------------------------------------
** G4MagIntegrationDriver: found case of zero momentum. iteration=  0 h= 1.07306
** G4MagIntegrationDriver: found case of zero momentum. iteration=  1 h= 0.107306
** G4MagIntegrationDriver: found case of zero momentum. iteration=  2 h= 0.0107306
** G4MagIntegrationDriver: found case of zero momentum. iteration=  3 h= 0.00107306
** G4MagIntegrationDriver: found case of zero momentum. iteration=  4 h= 0.000107306
** G4MagIntegrationDriver: found case of zero momentum. iteration=  5 h= 1.07306e-005
** G4MagIntegrationDriver: found case of zero momentum. iteration=  6 h= 1.07306e-006
** G4MagIntegrationDriver: found case of zero momentum. iteration=  7 h= 1.07306e-007
** G4MagIntegrationDriver: found case of zero momentum. iteration=  8 h= 1.07306e-008
** G4MagIntegrationDriver: found case of zero momentum. iteration=  9 h= 1.07306e-009
** G4MagIntegrationDriver: found case of zero momentum. iteration=  10 h= 1.07306e-010
** G4MagIntegrationDriver: found case of zero momentum. iteration=  11 h= 1.07306e-011
** G4MagIntegrationDriver: found case of zero momentum. iteration=  12 h= 1.07306e-012
** G4MagIntegrationDriver: found case of zero momentum. iteration=  13 h= 1.07306e-013
G4MagIntegratorDriver::OneGoodStep:
  Stepsize underflow in Stepper
  Step's start x=968.516 and end x= 968.516 are equal !!
  Due to step-size= 1.07306e-014 . Note that input step was 1.07306
//----------------------------------------------------------------------------------------------------

2)//----------------------------------------------------------------------------------------------------

*********************************************************************************************************
* G4Track Information:   Particle = e-,   Track ID = 2,   Parent ID = 1
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0     18.3     10.5     5.44  1.5e-005        0        0         0 Gas_in_cylinder_tube initStep
    1       18       11      5.6  1.5e-005        0     20.1      20.1 Gas_in_cylinder_tube eIoni
    2     18.6       11     5.55  1.5e-005        0     3.51      23.6 Gas_in_cylinder_tube msc
    3     19.1     10.9      5.5  1.5e-005        0     3.51      27.1 Gas_in_cylinder_tube msc
    4     19.6     10.9     5.45  1.5e-005        0     3.51      30.7 Gas_in_cylinder_tube msc
    5     20.1     10.9      5.4  1.5e-005        0     3.51      34.2 Gas_in_cylinder_tube msc
    6    -1.#J    -1.#J    -1.#J      1.#R        0     3.51      37.7 Gas_in_cylinder_tube msc
//----------------------------------------------------------------------------------------------------
where in this case the program is not responding anymore. I suppose case 2 is when an electron leaves the cylinder and goes to "infinity"?

3)//----------------------------------------------------------------------------------------------------

*********************************************************************************************************
* G4Track Information:   Particle = e-,   Track ID = 2,   Parent ID = 1
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0     14.5     12.9      117  1.5e-005        0        0         0 Gas_in_cylinder_tube initStep
    1     17.1     11.5      110  0.000387        0     20.1      20.1 Gas_in_cylinder_tube eIoni
    2       17    0.597      109      17.8        0     10.9        31 Gas_in_cylinder_tube msc
    3     11.9    0.659      107       822        0     6.96        38 Long_cylinder_tube Transportation
    4     10.8    0.635      107       822 2.61e-008     1.08      39.1 Long_cylinder_tube msc
    5     9.19    0.601      107 1.61e+006 3.87e-008     1.61      40.7       World Transportation
G4MagIntegratorDriver::OneGoodStep:
  Stepsize underflow in Stepper
  Step's start x=1007 and end x= 1007 are equal !!
  Due to step-size= 2.19296e-014 . Note that input step was 2.19296
G4MagIntegratorDriver::OneGoodStep:
  Stepsize underflow in Stepper
  Step's start x=1007 and end x= 1007 are equal !!
  Due to step-size= 2.19296e-014 . Note that input step was 2.19296
G4MagIntegratorDriver::OneGoodStep:
  Stepsize underflow in Stepper
  Step's start x=1008 and end x= 1008 are equal !!
  Due to step-size= 4.21789e-014 . Note that input step was 1.19296
    6  -1e+003     1.23      109 3.99e+024 2.14e-028 1.01e+003 1.05e+003  OutOfWorld Transportation
//----------------------------------------------------------------------------------------------------
In this case here, the voltage is set to +1V, and I've seen the same if the voltage is set to 0V. The incoming photon has a energy of 35eV, the electron after photoionization has 15eV  (with approx. 20eV being the Neon ionization potential). However, the kinetic energy of the electrons after 1-2 steps is more than 10 MeV, with a wire potential of 1V... 

For testing purposes I've altered my GetFieldValue function to the following code:
//----------------------------------------------------------------------------------------------------
void B7ElectricField::GetFieldValue(const G4double Point[3],G4double *Efield) const
{
	Efield[2] = 0.; //z component of electrical field is zero

	G4double X=Point[0], Y=Point[1];
	G4double U=1.*volt;

	Efield[0]=0;
	Efield[1]=U/1.6*cm;
}
//----------------------------------------------------------------------------------------------------
and the output is of the form in cases 1-3. Do you have any idea, where the error may lie?

Thanks & best regards, Robert

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1 News: Re: Electrons not affected by electric field?   (Robert Schaefer - 20 Jan, 2015)
(_ None: Re: Electrons not affected by electric field?   (John Apostolakis - 21 Jan, 2015)
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