geant4模拟阿尔法衰变代码

以下是一个使用Geant4模拟阿尔法衰变的示例代码供参考：

#include "G4RunManager.hh"
#include "G4UImanager.hh"
#include "G4UIExecutive.hh"
#include "G4UIterminal.hh"
#include "G4VisExecutive.hh"
#include "G4VModularPhysicsList.hh"
#include "G4EmStandardPhysics.hh"
#include "G4NistManager.hh"
#include "G4Box.hh"
#include "G4Tubs.hh"
#include "G4PVPlacement.hh"
#include "G4LogicalVolume.hh"
#include "G4VPhysicalVolume.hh"
#include "G4SystemOfUnits.hh"
#include "G4ParticleTable.hh"
#include "G4IonTable.hh"
#include "G4ParticleDefinition.hh"
#include "G4GenericIon.hh"
#include "G4Event.hh"
#include "G4PrimaryParticle.hh"
#include "G4PrimaryVertex.hh"
#include "Randomize.hh"

int main(int argc, char** argv) {
  // 初始化G4运行管理器
  G4RunManager* runManager = new G4RunManager;

  // 注册G4物理列表
  G4VModularPhysicsList* physicsList = new G4VModularPhysicsList;
  physicsList->RegisterPhysics(new G4EmStandardPhysics);
  runManager->SetUserInitialization(physicsList);

  // 构造几何形状
  G4NistManager* nist = G4NistManager::Instance();
  G4Box* worldBox = new G4Box("World", 10*m, 10*m, 10*m);
  G4LogicalVolume* worldLog = new G4LogicalVolume(worldBox, nist->FindOrBuildMaterial("G4_AIR"), "World");
  G4VPhysicalVolume* worldPhys = new G4PVPlacement(0, G4ThreeVector(), worldLog, "World", 0, false, 0);

  G4Tubs* sourceTube = new G4Tubs("Source", 0, 1*cm, 1*cm, 0, 2*pi);
  G4LogicalVolume* sourceLog = new G4LogicalVolume(sourceTube, nist->FindOrBuildMaterial("G4_Al"), "Source");
  new G4PVPlacement(0, G4ThreeVector(), sourceLog, "Source", worldLog, false, 0);

  // 定义粒子种类和能量
  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  G4ParticleDefinition* alpha = particleTable->GetIonTable()->GetIon(2, 4, 0);
  G4double energy = 5.48*MeV;

  // 创建主粒子
  G4PrimaryParticle* primary = new G4PrimaryParticle(alpha, energy, 0, 0, G4ThreeVector(0, 0, 1));
  G4PrimaryVertex* vertex = new G4PrimaryVertex(G4ThreeVector(0, 0, -5*cm), 0);
  vertex->SetPrimary(primary);

  // 生成事件并打印结果
  G4Event event;
  event.AddPrimaryVertex(vertex);
  event.Print();
  
  // 开始模拟
  runManager->BeamOn(1);

  // 释放资源
  delete runManager;

  return 0;
}

这个示例代码创建了一个包含一个半径为1cm、长度为2cm的铝源的几何形状，并在源的朝向上发射一个5.48MeV的$\alpha$粒子。运行时，它将生成一个事件并在控制台上打印结果，并通过Geant4模拟出该事件的物理行为。