DetectorConstruction.cxx

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#include "messagefacility/MessageLogger/MessageLogger.h"
#include "cetlib_except/exception.h"

#include "nutools/G4Base/DetectorConstruction.h"
#include "nutools/MagneticField/MagneticField.h"

#include "Geant4/G4VPhysicalVolume.hh"
#include "Geant4/G4GDMLParser.hh"
#include "Geant4/G4LogicalVolumeStore.hh"
#include "Geant4/G4Material.hh"
#include "Geant4/G4UniformMagField.hh"
#include "Geant4/G4FieldManager.hh"

namespace g4b{

  // Allocate static variables.
  G4VPhysicalVolume* DetectorConstruction::fWorld    = nullptr;
  G4FieldManager*    DetectorConstruction::fFieldMgr = nullptr;

  //---------------------------------------------------
  // Constructor
  DetectorConstruction::DetectorConstruction(std::string const& gdmlFile,
                                             bool        const& overlapCheck,
                                             bool        const& validateSchema)
  {
    if ( gdmlFile.empty() ) {
      throw cet::exception("DetectorConstruction") << "Supplied GDML filename is empty\n"
                                                   << __FILE__ << ":" << __LINE__ << "\n";
    }
    // Get the path to the GDML file from the Geometry interface.
    const G4String GDMLfile = static_cast<const G4String>( gdmlFile );

    // Use Geant4's GDML parser to convert the geometry to Geant4 format.
    G4GDMLParser parser;
    parser.SetOverlapCheck(overlapCheck);
    parser.Read(GDMLfile,validateSchema);

    // Fetch the world physical volume from the parser.  This contains
    // the entire detector, not just the outline of the experimental
    // hall.
    fWorld = parser.GetWorldVolume();
    
  }
  
  //---------------------------------------------------
  // Destructor.
  DetectorConstruction::~DetectorConstruction() 
  {
  }
  
  //---------------------------------------------------
  G4VPhysicalVolume* DetectorConstruction::Construct()
  {
    // Setup the magnetic field situation 
    art::ServiceHandle<mag::MagneticField> bField;
    
    // loop over the possible fields
    for(auto fd : bField->Fields()){
      switch (fd.fMode) {
        case mag::kNoBFieldMode:
          /* NOP */
          break;
        case mag::kConstantBFieldMode: {
          // Attach this to the magnetized volume only, so get that volume
          G4LogicalVolume *bvol = G4LogicalVolumeStore::GetInstance()->GetVolume(fd.fVolume);
          
          // Define the basic field, using p we should get the uniform field
          G4UniformMagField* magField = new G4UniformMagField( fd.fField * CLHEP::tesla );
          fFieldMgr = new G4FieldManager();
          fFieldMgr->SetDetectorField(magField);
          fFieldMgr->CreateChordFinder(magField);
          
          LOG_INFO("DetectorConstruction")
          << "Setting uniform magnetic field to be "
          << magField->GetConstantFieldValue().x() << " "
          << magField->GetConstantFieldValue().y() << " "
          << magField->GetConstantFieldValue().z() << " "
          << " in " << bvol->GetName();
          
          // Reset the chord finding accuracy
          // fFieldMgr->GetChordFinder()->SetDeltaChord(1.0 * cm);
          
          // the boolean tells the field manager to use local volume
          bvol->SetFieldManager(fFieldMgr, true);
          
          break;
        } // case mag::kConstantBFieldMode
        default: // Complain if the user asks for something not handled
          LOG_ERROR("DetectorConstruction")
          << "Unknown or illegal Magneticfield "
          << "mode specified: " 
          << fd.fMode
          << ". Note that AutomaticBFieldMode is reserved.";
          break;
      } // end switch cases
      
    } // end loop over fields
    
    return fWorld;
  }

}// namespace