Dear GDML-Team,

I want to simulate particle scattering in a beamline and therefore I need Quadrupoles/Sextupoles. 

Unfortunately G4QuadrupoleMagField uses the origin of the world volume to calculate the magnetic field (see Bugzilla/Geant4 – Problem 1085, John Apostolakis).

I also want to implement ionoptics to calculate the trajectory. For this purpose I need ionoptical coordinates that are related to the reference trajectory in the middle of the volume.

To solve this problem I need information about the position of the volume with magnetic field:

G4VPhysicalVolume->GetObjectTranslation(),
G4VPhysicalVolume->GetFrameTranslation(),
G4VPhysicalVolume->GetTranslation();
	
Using GDML Modules it seems not to be possible to retrieve the needed position information with these methods.

Thanks for your help and best regards,
Björn Riese.

---------------------------------------------------


The quadrupole is defined as modul in the main file esr.gdml ...

<physvol>
        <file name="E01QS0D.gdml"/>
        <positionref ref="E01QS0D_pos"/>
        <rotationref ref="E01QS0D_rot"/>
</physvol>

... and represents the whole quadrupole with its magnetic field ...

<structure>
	<volume name="E01QS0D_Mag_vol">
		<materialref ref="Vacuum"/>
		<solidref ref="E01QS0D_Mag_sol"/>
		<auxiliary auxtype="Quadrupole" auxvalue="GRADIENT"/>
	</volume> 

.... and placed as ...

        <physvol name="E01QS0D_Mag_phys">
		<volumeref ref="E01QS0D_Mag_vol"/>
        </physvol>

in the volume "E01QS0D".

---------------------------------------------------

Here the output of my application:

d01_tube_vol
world
d01_tube
(0,0,2335.35)
(-0,-0,-2335.35)
(0,0,2335.35)
-----               OK
d02_tube_vol
world
d02_tube
(0,0,4773.2)
(-0,-0,-4773.2)
(0,0,4773.2)
-----                OK
d03_tube_vol
world
d03_tube
(0,0,4923.2)
(-0,-0,-4923.2)
(0,0,4923.2)
-----                OK
d04_tube_vol             // (*lvciter)->GetName();
E01QS0D                  // (*pvciter)->GetMotherLogical()->GetName();
E01QS0D_Mag              // (*pvciter)->GetName();
(0,0,0)                  // (*pvciter)->GetObjectTranslation()
(-0,-0,-0)               // (*pvciter)->GetFrameTranslation()
(0,0,0)                  // (*pvciter)->GetTranslation()
-----                error:
-> d04_tube ist the beamline element after the first quadrupole!
   G4LogicalVolumeStore and G4PhysicalVolumeStore are not in same order!
-> the position is wrong if I use a GDML-Module:
<physvol>
        <file name="E01QS0D.gdml"/>
        <positionref ref="E01QS0D_pos"/>
        <rotationref ref="E01QS0D_rot"/>
</physvol>


-------------------------------------------------

A section of my DetectorConstruction class:

G4VPhysicalVolume* fWorldPhysVol;

    // Reading GDML files, Volume Auxiliary Information
    //
    if(fChoice==0) {
           parser.Read(fReadFile);
        fWorldPhysVol = parser.GetWorldVolume();
                                              
    ////////////////////////////////////////////////////////
    //          Begin of Auxiliary Information block
    //

           const G4LogicalVolumeStore* lvs =            
           G4LogicalVolumeStore::GetInstance();
           std::vector<G4LogicalVolume*>::const_iterator lvciter;
       
        const G4PhysicalVolumeStore* pvs =
            G4PhysicalVolumeStore::GetInstance();
        std::vector<G4VPhysicalVolume*>::const_iterator pvciter;

           for( lvciter = lvs->begin(), pvciter = pvs->begin();
            lvciter != lvs->end(); lvciter++, pvciter++ ) {
           
                 G4GDMLAuxListType auxInfo =
            parser.GetVolumeAuxiliaryInformation(*lvciter);

                 std::vector<G4GDMLAuxPairType>::const_iterator    
                ipair = auxInfo.begin();
                 for( ipair = auxInfo.begin(); ipair !=    
                auxInfo.end(); ipair++ ) {
                       G4String lv_name=(*lvciter)->GetName();
                G4String pv_name=(*pvciter)->GetName();
                G4String mv_name=(*pvciter)->
                    GetMotherLogical()->GetName();
                       G4String type=ipair->type;
                       G4double value=ipair->value;
               
                G4cout << lv_name << G4endl;
                G4cout << mv_name << G4endl;
                G4cout << pv_name << G4endl;
        G4cout << (*pvciter)->GetObjectTranslation() << G4endl;
        G4cout << (*pvciter)->GetFrameTranslation() << G4endl;
        G4cout << (*pvciter)->GetTranslation() << G4endl;
                G4cout << "-----" << G4endl;
                 }
           
           }