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// $Id: G4NeutronKiller.hh,v 1.2 2007/06/01 07:53:26 ahoward Exp $
// GEANT4 tag $Name: geant4-09-02 $
//
//---------------------------------------------------------------------------
//
// ClassName:   G4NeutronKiller
//
// Description: The process to kill neutrons to save CPU
//
// Author:      V.Ivanchenko 26/09/00 for HARP software
//
//----------------------------------------------------------------------------
//
// Class description:
//
// G4NeutronKiller allows to remove unwanted neutrons from simulation in 
// order to improve CPU performance. There are two parameters:
//                 
// 1) low energy threshold for neutron kinetic energy (default 0)
// 2) time limit for neutron track (default DBL_MAX) 
// 
// These parameters can be changed via Set methods or by UI commands:
//   /physics_engine/neutron/energyCut
//   /physics_engine/neutron/timeLimit
//
// If a neutron track is killed no energy deposition is added to the step 
//

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#ifndef NeutronKiller_h
#define NeutronKiller_h 1

#include "globals.hh"
#include "G4VDiscreteProcess.hh"
#include "G4ParticleDefinition.hh"
#include "G4Step.hh"
#include "G4Track.hh"

class G4NeutronKillerMessenger;

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class G4NeutronKiller : public G4VDiscreteProcess
{
public:

  G4NeutronKiller(const G4String& processName = "nKiller",
		  G4ProcessType   aType = fNotDefined);

  virtual ~G4NeutronKiller();

  G4bool IsApplicable(const G4ParticleDefinition&);

  void  SetTimeLimit(G4double);

  void  SetKinEnergyLimit(G4double);

  G4double PostStepGetPhysicalInteractionLength( const G4Track& track,
						 G4double previousStepSize,
						 G4ForceCondition* condition);

  G4VParticleChange* PostStepDoIt(const G4Track&, const G4Step&);

  G4double GetMeanFreePath(const G4Track&, G4double,G4ForceCondition*);

private:

  // hide assignment operator as private
  G4NeutronKiller(const G4NeutronKiller&);
  G4NeutronKiller& operator = (const G4NeutronKiller &right);

  G4double kinEnergyThreshold;
  G4double timeThreshold;
     
  G4NeutronKillerMessenger* pMess;
};

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inline G4double G4NeutronKiller::PostStepGetPhysicalInteractionLength( 
				 const G4Track& aTrack,
				 G4double, G4ForceCondition* condition)
{
  // condition is set to "Not Forced"
  *condition = NotForced;
  
  G4double limit = DBL_MAX; 
  if(aTrack.GetGlobalTime() > timeThreshold || 
     aTrack.GetKineticEnergy() < kinEnergyThreshold) limit = 0.0;
  return limit;
}

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inline G4double G4NeutronKiller::GetMeanFreePath(const G4Track&,G4double,
						 G4ForceCondition*)
{
  return DBL_MAX;
}    

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inline G4VParticleChange* G4NeutronKiller::PostStepDoIt(const G4Track& aTrack, 
							const G4Step&)
{
  pParticleChange->Initialize(aTrack);
  pParticleChange->ProposeTrackStatus(fStopAndKill);
  return pParticleChange;
}

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#endif