StandardFieldSvc.h

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/*
  Copyright (C) 2002-2022 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef G4ATLASSERVICES_StandardFieldSvc_H
#define G4ATLASSERVICES_StandardFieldSvc_H
 
// STL library
#include <string>
 
// Geant4
#include "G4MagneticField.hh"
 
// Gaudi/Athena
#include "GaudiKernel/ServiceHandle.h"
#include "G4AtlasInterfaces/IMagFieldSvc.h"
 
// Base classes
#include "G4MagFieldSvcBase.h"
 
// MagField cache
#include "MagFieldElements/AtlasFieldCache.h"
 
// forward declarations
namespace MagField {
    class AtlasFieldMap;
}

class AtlasField : public G4MagneticField
{
  public:
  AtlasField(double scaleSolenoid, double scaleToroid, const MagField::AtlasFieldMap* fieldMap)
    : m_fieldCache (MagField::AtlasFieldCache( scaleSolenoid, scaleToroid, fieldMap))
  {
    }

    AtlasField(MagField::IMagFieldSvc* m) :
        m_magFieldSvc(m)
        {}
 
 
    MagField::AtlasFieldCache& fieldCache() { return m_fieldCache; }

    void GetFieldValue(const double *point, double *field) const
    {
        if (m_magFieldSvc) m_magFieldSvc->getField(point, field);
        else               m_fieldCache.getField(point, field);
    }
 
  private:
    mutable MagField::AtlasFieldCache m_fieldCache ATLAS_THREAD_SAFE;

    MagField::IMagFieldSvc* m_magFieldSvc{nullptr};
};
 

class StandardFieldSvc final : public G4MagFieldSvcBase
{
  public:

    StandardFieldSvc(const std::string& name, ISvcLocator* pSvcLocator);
    ~StandardFieldSvc() = default;

    StatusCode initialize() override final;
 
  protected:
    G4MagneticField* makeField() override final;
 
  private:
 
    // There are two options for the magnetic field:
    //
    // 1) For solenoid and toroid, this has moved to use AtlasFieldCache and here we must create and
    //    same the field map
    // 2) For the forward quadrupole fields, we preserve the access to the magnetic field service
    //
    // The boolean flag UseMagFieldSvc is now used to differentiate between the two cases (default is false)
    //
 
    // flag to use magnet field service
    Gaudi::Property<bool> m_useMagFieldSvc {this,
            "UseMagFieldSvc", false, "Use magnetic field service - Should ONLY be used for ForwardRegionFieldSvc"};

    ServiceHandle<MagField::IMagFieldSvc> m_magFieldSvc {this, "MagneticFieldSvc", ""};
 
    StatusCode createFieldMap();
 
    // properties taken from AtlasFieldMapCondAlg
    bool solenoidOn() { return (m_mapSoleCurrent > 0.0); }
    bool toroidOn()   { return (m_mapToroCurrent > 0.0); }

    Gaudi::Property<std::string> m_fullMapFilename {this,
            "FullMapFile", "MagneticFieldMaps/bfieldmap_7730_20400_14m.root",
            "File storing the full magnetic field map"};
    Gaudi::Property<std::string> m_soleMapFilename {this,
                                                    "SoleMapFile", "MagneticFieldMaps/bfieldmap_7730_0_14m.root",
                                                    "File storing the solenoid-only magnetic field map"};
    Gaudi::Property<std::string> m_toroMapFilename {this,
                                                    "ToroMapFile", "MagneticFieldMaps/bfieldmap_0_20400_14m.root",
                                                    "File storing the toroid-only magnetic field map"};

    Gaudi::Property<double>      m_mapSoleCurrent  {this,
                                                    "MapSoleCurrent", 7730., "Nominal solenoid current (A)"};
    Gaudi::Property<double>      m_mapToroCurrent  {this,
                                                    "MapToroCurrent", 20400., "Nominal toroid current (A)"};

    Gaudi::Property<double>      m_useSoleCurrent  {this,
                                                    "UseSoleCurrent", 7730., "Configured solenoid current (A)"};
    Gaudi::Property<double>      m_useToroCurrent  {this,
                                                    "UseToroCurrent", 20400., "Configured toroid current (A)"};
 
    // field map held locally in svc - in Athena, this would go into a conditions object
    std::unique_ptr<MagField::AtlasFieldMap> m_fieldMap;
};
 
#endif // G4ATLASSERVICES_StandardFieldSvc_H