Gabriele Cosmo
271 lines
12 KiB
C++
271 lines
12 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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//
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// -------------------------------------------------------------------
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//
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// GEANT4 Class header file
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//
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//
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// File name: G4eDPWAElasticDCS
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//
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// Author: Mihaly Novak
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//
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// Creation date: 02.07.2020
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//
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// Modifications:
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//
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// Class Description:
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//
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// Contains numerical Differential Cross Sections (DCS) for e-/e+ Coulomb
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// scattering computed by Dirac Partial Wave Analysis (DPWA) [1]:
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// - electrostatic interaction, with a local exchange correction in the case of
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// electrons (using Dirac-Fock e- densities; finite nuclear size with Fermi
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// charge distribution; exchange potential with Furness and McCarthy for e-)[2]
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// - correlation-polarization (projectiles cause the polarization of the charge
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// cloud of the target atom and the induced dipole moment acts back on the
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// projectile) was accounted by using Local-Density Approximation (LDA) [2]
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// - absorption: not included since it's an inelastic channel [2] (the cor-
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// responding excitations needs to be modelled by a separate, independent,
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// inelastic model).
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// Using the above mentioned DPWA computation with a free atom approximation
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// might lead to questionable results below few hundred [eV] where possible
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// solid state or bounding effects might start to affect the potential.
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// Nevertheless, the lower energy was set to 10 eV in order to provide(at least)
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// some model even at low energies (with this caution). The highest projectile
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// kinetic energy is 100 [MeV].
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//
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// The class provides interface methods for elastic, first-, second-transport
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// cross section computations as well as for sampling cosine of polar angular
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// deflections. These interface methods are also available for resricted cross
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// section computations and angular deflection sampling.
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//
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// References:
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//
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// [1] Salvat, F., Jablonski, A. and Powell, C.J., 2005. ELSEPA—Dirac partial-
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// wave calculation of elastic scattering of electrons and positrons by
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// atoms, positive ions and molecules. Computer physics communications,
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// 165(2), pp.157-190.
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// [2] Salvat, F., 2003. Optical-model potential for electron and positron
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// elastic scattering by atoms. Physical Review A, 68(1), p.012708.
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// [3] Benedito, E., Fernández-Varea, J.M. and Salvat, F.,2001. Mixed simulation
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// of the multiple elastic scattering of electrons and positrons using
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// partial-wave differential cross-sections. Nuclear Instruments and Methods
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// in Physics Research Section B: Beam Interactions with Materials and Atoms,
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// 174(1-2), pp.91-110.
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//
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// -------------------------------------------------------------------
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#ifndef G4eDPWAElasticDCS_h
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#define G4eDPWAElasticDCS_h 1
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#include <vector>
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#include <fstream>
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#include <iomanip>
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#include <sstream>
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#include "globals.hh"
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#include "G4String.hh"
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#include "G4Physics2DVector.hh"
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#include "G4MaterialTable.hh"
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#include "G4Material.hh"
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#include "G4Element.hh"
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#include "G4MaterialCutsCouple.hh"
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#include "G4ProductionCutsTable.hh"
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#include "G4Log.hh"
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#include "G4Exp.hh"
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class G4eDPWAElasticDCS {
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public:
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// CTR:
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// - iselectron : data for e- (for e+ otherwise)
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// - isrestricted : sampling of angular deflection on restricted interavl is
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// required (i.e. in case of mixed-simulation models)
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G4eDPWAElasticDCS(G4bool iselectron=true, G4bool isrestricted=false);
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// DTR
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~G4eDPWAElasticDCS();
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// initialise for a given 'iz' atomic number:
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// - nothing happens if it has already been initialised for that Z.
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void InitialiseForZ(std::size_t iz);
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// Computes the elastic, first and second cross sections for the given kinetic
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// energy and target atom.
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// Cross sections are zero ff ekin is below/above the kinetic energy grid
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void ComputeCSPerAtom(G4int iz, G4double ekin, G4double& elcs, G4double& tr1cs,
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G4double& tr2cs, G4double mumin=0.0, G4double mumax=1.0);
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// samples cos(theta) i.e. cosine of the polar angle of scattering in elastic
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// interaction (Coulomb scattering) of the projectile (e- or e+ depending on
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// fIsElectron) with kinetic energy of exp('lekin'), target atom with atomic
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// muber of 'iz'. See the 'SampleCosineThetaRestricted' for obtain samples on
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// a restricted inteval.
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G4double SampleCosineTheta(std::size_t iz, G4double lekin, G4double r1,
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G4double r2, G4double r3);
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// samples cos(theta) i.e. cosine of the polar angle of scattering in elastic
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// interaction (Coulomb scattering) of the projectile (e- or e+ depending on
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// fIsElectron) with kinetic energy of exp('lekin'), target atom with atomic
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// muber of 'iz'.
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// The cosine theta will be in the [costMin, costMax] interval where costMin
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// corresponds to a maximum allowed polar scattering angle thetaMax while
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// costMin corresponds to minimum allowed polar scatterin angle thetaMin.
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// See the 'SampleCosineTheta' for obtain samples on the entire [-1,1] range.
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G4double SampleCosineThetaRestricted(std::size_t iz, G4double lekin,
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G4double r1, G4double r2,
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G4double costMax, G4double costMin);
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// interpolate scattering power correction form table buit at init.
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G4double ComputeScatteringPowerCorrection(const G4MaterialCutsCouple *matcut,
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G4double ekin);
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// build scattering power correction table at init.
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void InitSCPCorrection(G4double lowEnergyLimit, G4double highEnergyLimit);
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private:
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// data structure to store one sampling table: combined Alias + RatIn
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// NOTE: when Alias is used, sampling on a resctricted interval is not possible
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// However, Alias makes possible faster sampling. Alias is used in case
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// of single scattering model while it's not used in case of mixed-model
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// when restricted interval sampling is needed. This is controlled by
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// the fIsRestrictedSamplingRequired flag (false by default).
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struct OneSamplingTable {
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OneSamplingTable () = default;
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void SetSize(std::size_t nx, G4bool useAlias) {
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fN = nx;
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// Alias
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if (useAlias) {
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fW.resize(nx);
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fI.resize(nx);
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}
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// Ratin
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fCum.resize(nx);
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fA.resize(nx);
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fB.resize(nx);
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}
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// members
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std::size_t fN; // # data points
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G4double fScreenParA; // the screening parameter
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std::vector<G4double> fW;
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std::vector<G4double> fCum;
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std::vector<G4double> fA;
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std::vector<G4double> fB;
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std::vector<G4int> fI;
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};
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// loads the kinetic energy and theta grids for the DCS data (first init step)
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// should be called only by the master
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void LoadGrid();
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// load DCS data for a given Z
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void LoadDCSForZ(G4int iz);
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// loads sampling table for the given Z over the enrgy grid
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void BuildSmplingTableForZ(G4int iz);
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G4double SampleMu(std::size_t izet, std::size_t ie, G4double r1, G4double r2);
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G4double FindCumValue(G4double u, const OneSamplingTable& stable,
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const std::vector<G4double>& uvect);
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// muMin and muMax : no checks on these
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G4double SampleMu(std::size_t izet, std::size_t ie, G4double r1, G4double muMin,
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G4double muMax);
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// set the DCS data directory path
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const G4String& FindDirectoryPath();
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// uncompress one data file into the input string stream
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void ReadCompressedFile(G4String fname, std::istringstream &iss);
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// compute Molier material dependent parameters
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void ComputeMParams(const G4Material* mat, G4double& theBc, G4double& theXc2);
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// members
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private:
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// indicates if the object is for mixed-simulation (single scatterin otherwise)
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G4bool fIsRestrictedSamplingRequired;
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// indicates if the object is for e- (for e+ otherwise)
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G4bool fIsElectron;
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// indicates if the ekin, mu grids has already been loaded (only once)
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static G4bool gIsGridLoaded;
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// data directory
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static G4String gDataDirectory;
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// max atomic number (Z) for which DCS has been computed (103)
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static constexpr std::size_t gMaxZ = 103;
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// energy and theta grid(s) relaed variables: loaded from gridinfo by LoadGrid
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static std::size_t gNumEnergies;
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static std::size_t gIndxEnergyLim;// the energy index just above 2 [keV]
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static std::size_t gNumThetas1; // used for e- below 2 [keV]
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static std::size_t gNumThetas2; // used for e+ and for e- bove 2 [keV]
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static std::vector<G4double> gTheEnergies; // log-kinetic energy grid
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static std::vector<G4double> gTheMus1; // mu(theta) = 0.5[1-cos(theta)]
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static std::vector<G4double> gTheMus2;
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static std::vector<G4double> gTheU1; // u(mu; A'=0.01) = (A'+1)mu/(mu+A')
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static std::vector<G4double> gTheU2;
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static G4double gLogMinEkin; // log(gTheEnergies[0])
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static G4double gInvDelLogEkin;// 1./log(gTheEnergies[i+1]/gTheEnergies[i])
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// abscissas and weights of an 8 point Gauss-Legendre quadrature
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// for numerical integration on [0,1]
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static const G4double gXGL[8];
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static const G4double gWGL[8];
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//
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std::vector<G4Physics2DVector*> fDCS; // log(DCS) data per Z
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std::vector<G4Physics2DVector*> fDCSLow; // only for e- E < 2keV
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// sampling tables: only one of the followings will be utilized
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std::vector< std::vector<OneSamplingTable>* > fSamplingTables;
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//
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// scattering power correction: to account sub-threshold inelastic deflections
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const G4int fNumSPCEbinPerDec = 3;
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struct SCPCorrection {
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G4bool fIsUse; //
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G4double fPrCut; // sec. e- production cut energy
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G4double fLEmin; // log min energy
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G4double fILDel; // inverse log delta kinetic energy
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std::vector<G4double> fVSCPC; // scattering power correction vector
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};
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std::vector<SCPCorrection*> fSCPCPerMatCuts;
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};
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#endif
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