Import Geant4 10.7.0.beta source tree
This commit is contained in:
Gabriele Cosmo
@@ -41,6 +41,7 @@
|
||||
// 06-02-06 ComputeCrossSectionPerElectron, ComputeCrossSectionPerAtom (mma)
|
||||
// 29-06-06 Fix problem for zero energy incident positron (V.Ivanchenko)
|
||||
// 20-10-06 Add theGamma as a member (V.Ivanchenko)
|
||||
// 18-01-20 Introduce thermal model of annihilation at rest (J.Allison)
|
||||
//
|
||||
//
|
||||
// Class Description:
|
||||
@@ -54,13 +55,12 @@
|
||||
//
|
||||
// GEANT4 internal units.
|
||||
//
|
||||
// Note 1: The initial electron is assumed free and at rest.
|
||||
// Note 1: The initial electron is assumed free and at rest if atomic PDF
|
||||
// is not defined
|
||||
//
|
||||
// Note 2: The annihilation processes producing one or more than two photons are
|
||||
// ignored, as negligible compared to the two photons process.
|
||||
|
||||
|
||||
|
||||
//
|
||||
// -------------------------------------------------------------------
|
||||
//
|
||||
@@ -75,7 +75,9 @@
|
||||
#include "G4Positron.hh"
|
||||
#include "G4Gamma.hh"
|
||||
#include "Randomize.hh"
|
||||
#include "G4RandomDirection.hh"
|
||||
#include "G4ParticleChangeForGamma.hh"
|
||||
#include "G4EmParameters.hh"
|
||||
#include "G4Log.hh"
|
||||
#include "G4Exp.hh"
|
||||
|
||||
@@ -83,6 +85,8 @@
|
||||
|
||||
using namespace std;
|
||||
|
||||
G4bool G4eeToTwoGammaModel::fSampleAtomicPDF = false;
|
||||
|
||||
G4eeToTwoGammaModel::G4eeToTwoGammaModel(const G4ParticleDefinition*,
|
||||
const G4String& nam)
|
||||
: G4VEmModel(nam),
|
||||
@@ -102,6 +106,26 @@ G4eeToTwoGammaModel::~G4eeToTwoGammaModel()
|
||||
void G4eeToTwoGammaModel::Initialise(const G4ParticleDefinition*,
|
||||
const G4DataVector&)
|
||||
{
|
||||
if(IsMaster()) {
|
||||
G4int verbose = G4EmParameters::Instance()->Verbose();
|
||||
// redo initialisation for each new run
|
||||
fSampleAtomicPDF = false;
|
||||
const auto& materialTable = G4Material::GetMaterialTable();
|
||||
for (const auto& material: *materialTable) {
|
||||
const G4double meanEnergyPerIonPair = material->GetIonisation()->GetMeanEnergyPerIonPair();
|
||||
if (meanEnergyPerIonPair > 0.) {
|
||||
fSampleAtomicPDF = true;
|
||||
if(verbose > 0) {
|
||||
G4cout << "### G4eeToTwoGammaModel: for " << material->GetName() << " mean energy per ion pair is "
|
||||
<< meanEnergyPerIonPair/CLHEP::eV << " eV" << G4endl;
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
// If no materials have meanEnergyPerIonPair set. This is probably the usual
|
||||
// case, since most applications are not senstive to the slight
|
||||
// non-collinearity of gammas in eeToTwoGamma. Do not issue any warning.
|
||||
|
||||
if(fParticleChange) { return; }
|
||||
fParticleChange = GetParticleChangeForGamma();
|
||||
}
|
||||
@@ -135,9 +159,7 @@ G4double G4eeToTwoGammaModel::ComputeCrossSectionPerAtom(
|
||||
G4double, G4double, G4double)
|
||||
{
|
||||
// Calculates the cross section per atom of annihilation into two photons
|
||||
|
||||
G4double cross = Z*ComputeCrossSectionPerElectron(kineticEnergy);
|
||||
return cross;
|
||||
return Z*ComputeCrossSectionPerElectron(kineticEnergy);
|
||||
}
|
||||
|
||||
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
|
||||
@@ -149,19 +171,16 @@ G4double G4eeToTwoGammaModel::CrossSectionPerVolume(
|
||||
G4double, G4double)
|
||||
{
|
||||
// Calculates the cross section per volume of annihilation into two photons
|
||||
|
||||
G4double eDensity = material->GetElectronDensity();
|
||||
G4double cross = eDensity*ComputeCrossSectionPerElectron(kineticEnergy);
|
||||
return cross;
|
||||
return material->GetElectronDensity()*ComputeCrossSectionPerElectron(kineticEnergy);
|
||||
}
|
||||
|
||||
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
|
||||
|
||||
// Polarisation of gamma according to M.H.L.Pryce and J.C.Ward,
|
||||
// Polarisation of gamma according to M.H.L.Pryce and J.C.Ward,
|
||||
// Nature 4065 (1947) 435.
|
||||
|
||||
void G4eeToTwoGammaModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp,
|
||||
const G4MaterialCutsCouple*,
|
||||
const G4MaterialCutsCouple* pCutsCouple,
|
||||
const G4DynamicParticle* dp,
|
||||
G4double,
|
||||
G4double)
|
||||
@@ -173,26 +192,81 @@ void G4eeToTwoGammaModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp,
|
||||
|
||||
// Case at rest
|
||||
if(posiKinEnergy == 0.0) {
|
||||
G4double cost = 2.*rndmEngine->flat()-1.;
|
||||
G4double sint = sqrt((1. - cost)*(1. + cost));
|
||||
G4double phi = twopi * rndmEngine->flat();
|
||||
G4ThreeVector dir(sint*cos(phi), sint*sin(phi), cost);
|
||||
phi = twopi * rndmEngine->flat();
|
||||
G4double cosphi = cos(phi);
|
||||
G4double sinphi = sin(phi);
|
||||
G4ThreeVector pol(cosphi, sinphi, 0.0);
|
||||
pol.rotateUz(dir);
|
||||
aGamma1 = new G4DynamicParticle(theGamma, dir, electron_mass_c2);
|
||||
aGamma1->SetPolarization(pol.x(),pol.y(),pol.z());
|
||||
aGamma2 = new G4DynamicParticle(theGamma,-dir, electron_mass_c2);
|
||||
pol.set(-sinphi, cosphi, 0.0);
|
||||
pol.rotateUz(dir);
|
||||
aGamma2->SetPolarization(pol.x(),pol.y(),pol.z());
|
||||
/*
|
||||
G4cout << "Annihilation at rest fly: e0= " << " dir= " << dir
|
||||
<< G4endl;
|
||||
*/
|
||||
} else {
|
||||
|
||||
const G4double eGamma = electron_mass_c2;
|
||||
|
||||
// In rest frame of positronium gammas are back to back
|
||||
const G4ThreeVector& dir1 = G4RandomDirection();
|
||||
const G4ThreeVector& dir2 = -dir1;
|
||||
aGamma1 = new G4DynamicParticle(G4Gamma::Gamma(),dir1,eGamma);
|
||||
aGamma2 = new G4DynamicParticle(G4Gamma::Gamma(),dir2,eGamma);
|
||||
|
||||
// In rest frame the gammas are polarised perpendicular to each other - see
|
||||
// Pryce and Ward, Nature No 4065 (1947) p.435.
|
||||
// Snyder et al, Physical Review 73 (1948) p.440.
|
||||
G4ThreeVector pol1 = (G4RandomDirection().cross(dir1)).unit();
|
||||
G4ThreeVector pol2 = (pol1.cross(dir2)).unit();
|
||||
|
||||
// But the positronium is moving...
|
||||
// A positron in matter slows down and combines with an atomic electron to
|
||||
// make a neutral “atom” called positronium, about half the size of a normal
|
||||
// atom. I expect that when the energy of the positron is small enough,
|
||||
// less than the binding energy of positronium (6.8 eV), it is
|
||||
// energetically favourable for an electron from the outer orbitals of a
|
||||
// nearby atom or molecule to transfer and bind to the positron, as in an
|
||||
// ionic bond, leaving behind a mildly ionised nearby atom/molecule. I
|
||||
// would expect the positronium to come away with a kinetic energy of a
|
||||
// few eV on average. In its para (spin 0) state it annihilates into two
|
||||
// photons, which in the rest frame of the positronium are collinear
|
||||
// (back-to-back) due to momentum conservation. Because of the motion of the
|
||||
// positronium, photons will be not quite back-to-back in the laboratory.
|
||||
|
||||
// The positroniuim acquires an energy of order its binding energy and
|
||||
// doesn't have time to thermalise. Nevertheless, here we approximate its
|
||||
// energy distribution by a Maxwell-Boltzman with mean energy <KE>. In terms
|
||||
// of a more familiar concept of temperature, and the law of equipartition
|
||||
// of energy of translational motion, <KE>=3kT/2. Each component of velocity
|
||||
// has a distribution exp(-mv^2/2kT), which is a Gaussian of mean zero
|
||||
// and variance kT/m=2<KE>/3m, where m is the positronium mass.
|
||||
|
||||
// We take <KE> = material->GetIonisation()->GetMeanEnergyPerIonPair().
|
||||
|
||||
if(fSampleAtomicPDF) {
|
||||
const G4Material* material = pCutsCouple->GetMaterial();
|
||||
const G4double meanEnergyPerIonPair = material->GetIonisation()->GetMeanEnergyPerIonPair();
|
||||
const G4double& meanKE = meanEnergyPerIonPair; // Just an alias
|
||||
if (meanKE > 0.) { // Positronium haas motion
|
||||
// Mass of positronium
|
||||
const G4double mass = 2.*electron_mass_c2;
|
||||
// Mean <KE>=3kT/2, as described above
|
||||
// const G4double T = 2.*meanKE/(3.*k_Boltzmann);
|
||||
// Component velocities: Gaussian, variance kT/m=2<KE>/3m.
|
||||
const G4double sigmav = std::sqrt(2.*meanKE/(3.*mass));
|
||||
// This is in units where c=1
|
||||
const G4double vx = G4RandGauss::shoot(0.,sigmav);
|
||||
const G4double vy = G4RandGauss::shoot(0.,sigmav);
|
||||
const G4double vz = G4RandGauss::shoot(0.,sigmav);
|
||||
const G4ThreeVector v(vx,vy,vz); // In unit where c=1
|
||||
const G4ThreeVector& beta = v; // so beta=v/c=v
|
||||
|
||||
aGamma1->Set4Momentum(aGamma1->Get4Momentum().boost(beta));
|
||||
aGamma2->Set4Momentum(aGamma2->Get4Momentum().boost(beta));
|
||||
|
||||
// Rotate polarisation vectors
|
||||
const G4ThreeVector& newDir1 = aGamma1->GetMomentumDirection();
|
||||
const G4ThreeVector& newDir2 = aGamma2->GetMomentumDirection();
|
||||
const G4ThreeVector& axis1 = dir1.cross(newDir1); // No need to be unit
|
||||
const G4ThreeVector& axis2 = dir2.cross(newDir2); // No need to be unit
|
||||
const G4double& angle1 = std::acos(dir1*newDir1);
|
||||
const G4double& angle2 = std::acos(dir2*newDir2);
|
||||
if (axis1 != G4ThreeVector()) pol1.rotate(axis1,angle1);
|
||||
if (axis2 != G4ThreeVector()) pol2.rotate(axis2,angle2);
|
||||
}
|
||||
}
|
||||
aGamma1->SetPolarization(pol1.x(),pol1.y(),pol1.z());
|
||||
aGamma2->SetPolarization(pol2.x(),pol2.y(),pol2.z());
|
||||
|
||||
} else { // Positron interacts in flight
|
||||
|
||||
G4ThreeVector posiDirection = dp->GetMomentumDirection();
|
||||
|
||||
|
||||
Reference in New Issue
Block a user