StackingAction

前面介绍的 RunAction 和 StepingAction 都只能用来提取数据，不能改变粒子的模拟状态，而这里 StackingAction 则可以改变粒子模拟的先后顺序，甚至直接 kill 该粒子。

#include "G4ClassificationOfNewTrack.hh"

class G4UserStackingAction
{
  public:
      G4UserStackingAction();
      virtual ~G4UserStackingAction();
  protected:
      G4StackManager * stackManager;

  public:
//---------------------------------------------------------------
// virtual methods to be implemented by user
//---------------------------------------------------------------
//
      virtual G4ClassificationOfNewTrack ClassifyNewTrack(const G4Track*);
      virtual void NewStage();
      virtual void PrepareNewEvent();
};

这个类有三个虚函数，ClassifyNewTrack、NewStage 和 PrepareNewEvent，用户可以重写它们来控制各种模拟 track 堆叠机制。

每当 G4EventManager 将新的 G4Track 对象 “推” 到堆栈上时，G4StackManager 就会调用 ClassifyNewTrack()。ClassifyNewTrack() 返回枚举器 G4ClassificationOfNewTrack，其值指示 track 将发送到哪个堆栈（如果有）。该值应由用户确定。

G4ClassificationOfNewTrack 有四个可能的值：

ClassifyNewTrack

#include "G4VProcess.hh"

G4ClassificationOfNewTrack wuStackingActionAll::ClassifyNewTrack(const G4Track* aTrack)
{
  G4int parent_ID = aTrack->get_parentID();
  //      parent_ID = 0 : primary particle
  //                > 0 : secondary particle
  //                < 0 : postponed from the previous event    


  return fUrgent;
}

典型示例

// 保留初级粒子
  if (aTrack->GetParentID() == 0) return fUrgent;

  // 杀掉所有次级粒子 
  return fKill;

常用筛选条件

// 需要添加头文件
#include "G4VProcess.hh"

 G4String PName = aTrack->GetDefinition()->GetParticleName();

 G4int TrackID = aTrack->GetTrackID();
 G4int ParentID = aTrack->GetParentID();

 G4String CreatorProcess;
 const G4VProcess* pcr = aTrack->GetCreatorProcess();
 if(pcr) CreatorProcess = pcr->GetProcessName();
 else CreatorProcess = "##";

// 不模拟所有非中子粒子
 if(PName[0] != 'n') return fKill;
 return fUrgent;

// 不模拟生成时间大于 100 ns 的粒子
if(aTrack->GetGlobalTime() > 100*ns) return fKill;

NewStage

这里不介绍

PrepareNewEvent

这里不介绍

G4Track 常用函数

aTrack->GetTrackID();//G4int
  aTrack->GetParentID();//G4int
  aTrack->GetWeight();//G4double   These are methods for manipulating a weight for this track.
  aTrack->GetCreatorModelID();//G4int
  aTrack->GetCreatorModelName();//G4String&
  aTrack->GetCreatorProcess();//G4VProcess*
  const G4VProcess* pcr = aTrack->GetCreatorProcess();
  if(pcr) G4String CreatorProcess = pcr->GetProcessName();//  Returns the name of the process.
  else G4String CreatorProcess = "##";
  pcr->GetProcessType();//G4ProcessType    Returns the process type.
  pcr->GetProcessSubType();//G4int    Returns the process sub type.



  aTrack->GetTrackLength();//G4double
  // Before the end of the AlongStepDoIt loop,StepLength keeps the initial value which is determined by the shortest geometrical Step proposed by a physics process. After finishing the AlongStepDoIt, it will be set equal to 'StepLength' in G4Step.
  aTrack->GetStepLength();//G4double
  aTrack->GetCurrentStepNumber();//G4int
  aTrack->GetStep();//G4Step*
  // The flag of "GoodForTracking" is set by processes if this track should be tracked even if the energy is below threshold
  aTrack->IsGoodForTracking();//G4bool
  // The flag of "BelowThreshold" is set to true if this track energy is below threshold energy in this material determined by the range cut value
  aTrack->IsBelowThreshold();//G4bool
  aTrack->GetTrackStatus();//G4TrackStatus    track status, flags for tracking
  aTrack->GetPolarization();//G4ThreeVector& 
  aTrack->UseGivenVelocity();//G4bool
  aTrack->CalculateVelocity();//G4double
  aTrack->CalculateVelocityForOpticalPhoton();//G4double
  aTrack->GetVelocity();//G4double
  aTrack->GetMomentum();//G4ThreeVector
  aTrack->GetMomentumDirection();//G4ThreeVector&
  aTrack->GetTotalEnergy();//G4double
  aTrack->GetKineticEnergy();//G4double
  aTrack->GetVolume();//G4VPhysicalVolume*
  aTrack->GetNextVolume();//G4VPhysicalVolume*
  aTrack->GetMaterial();//G4Material*
  aTrack->GetNextMaterial();//G4Material*
  aTrack->GetMaterialCutsCouple();//G4MaterialCutsCouple*
  aTrack->GetNextMaterialCutsCouple();//G4MaterialCutsCouple*
  aTrack->GetTouchable();//G4VTouchable*
  aTrack->GetTouchableHandle();//G4TouchableHandle&
  aTrack->GetNextTouchable();//G4VTouchable*
  aTrack->GetNextTouchableHandle();//G4TouchableHandle&
  aTrack->GetOriginTouchable();//G4VTouchable*
  aTrack->GetOriginTouchableHandle();//G4TouchableHandle&
  aTrack->GetPosition();//G4ThreeVector&
  aTrack->GetGlobalTime();//G4double    Time since the event in which the track belongs is created.
  aTrack->GetLocalTime();//G4double    Time since the current track is created.
  aTrack->GetProperTime();//G4double    Proper time of the current track
  aTrack->GetDynamicParticle();//G4DynamicParticle*   dynamic particle 
  aTrack->GetParticleDefinition();//G4ParticleDefinition*    particle definition 


  // vertex (,where this track was created) information  
  aTrack->GetVertexPosition();//G4ThreeVector&
  aTrack->GetVertexMomentumDirection();//G4ThreeVector&
  aTrack->GetVertexKineticEnergy();//G4double
  aTrack->GetLogicalVolumeAtVertex();//G4LogicalVolume*


  aTrack->GetUserInformation();// G4VUserTrackInformation*
  aTrack->SetUserInformation(/*G4VUserTrackInformation* aValue*/);