|Message: Electric field array from a TOSCA simulation||Not Logged In (login)|
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Dear All, in order to simulate in all its detail a ionisation chamber I decided to insert in a GEANT4 simulation anot a simple uniform field but an array calculated from a TOSCA simulation. The TOSCA output is an array specifing the electric field value in each point of a given volume.
Inside the GEANT4 examples, the advanced Purg_Mag shows how read and insert a TOSCA file, but in that case the field is a magnetic field.
I tried to insert the TOSCA electric field but with bad results.
** When I run the code with electrons they show a very strange behaviour and this warning are reported:
---> Begin Of Event: 0 G4MagIntegratorDriver::OneGoodStep: Stepsize underflow in Stepper Step's start x=0.470003 and end x= 0.470003 are equal !! Due to step-size= 1.00213e-20 . Note that input step was 0.0100213 G4MagIntegratorDriver::OneGoodStep: Stepsize underflow in Stepper Step's start x=0.0600006 and end x= 0.0600006 are equal !! Due to step-size= 1.04199e-21 . Note that input step was 0.0104199 G4MagIntegratorDriver::OneGoodStep: Stepsize underflow in Stepper Step's start x=0.0800005 and end x= 0.0800005 are equal !! Due to step-size= 1.07168e-21 . Note that input step was 0.0107168 G4MagIntegratorDriver::OneGoodStep: Stepsize underflow in Stepper
** When I run with proton a segmentation fault is produced.
This is my DetectorConstruction.cc in which the TOSCA file (data1.table) is read and then the electric field "should be" activated:
G4ElectricField* myField= new PurgMagTabulatedField3D("data1.table", zOffset);
G4EqMagElectricField* fEquation = new G4EqMagElectricField(myField);
G4TransportationManager* pTransportMgr = G4TransportationManager::GetTransportationManager();
pFieldPropagator = pTransportMgr -> GetPropagatorInField();
pStepper = new G4ClassicalRK4(fEquation, 8);
pFieldMgr = pTransportMgr -> GetFieldManager();
pFieldMgr -> SetFieldChangesEnergy(true);
pFieldMgr -> SetDetectorField(myField);
pIntgrDriver = new G4MagInt_Driver(0.01 *mm, pStepper, pStepper -> GetNumberOfVariables());
pChordFinder = new G4ChordFinder(pIntgrDriver);
pFieldMgr -> SetChordFinder(pChordFinder);
The code function perfectly if I substitute the line
G4ElectricField* myField= new PurgMagTabulatedField3D("data1.table", zOffset)
G4UniformElectricField* myField = new G4UniformElectricField(G4ThreeVector(0,900 *kilovolt/cm, 0));
for an uniform electric field.
Can someone give me some indication on this problem? Thank you very much Pablo Cirrone
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