Gabriele Cosmo
251 lines
12 KiB
C++
251 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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// File name: G4GoudsmitSaundersonMscModel
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//
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// Author: Mihaly Novak / (Omrane Kadri)
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//
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// Creation date: 20.02.2009
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//
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// Modifications:
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// 04.03.2009 V.Ivanchenko cleanup and format according to Geant4 EM style
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// 12.05.2010 O.Kadri: adding Qn1 and Qn12 as private doubles
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// 18.05.2015 M. Novak provide PLERIMINARYY version of updated class.
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// All algorithms of the class were revised and updated, new methods added.
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// A new version of Kawrakow-Bielajew Goudsmit-Saunderson MSC model
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// based on the screened Rutherford DCS for elastic scattering of
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// electrons/positrons has been introduced[1,2]. The corresponding MSC
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// angular distributions over a 2D parameter grid have been recomputed
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// and the CDFs are now stored in a variable transformed (smooth) form[2,3]
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// together with the corresponding rational interpolation parameters.
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// These angular distributions are handled by the new
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// G4GoudsmitSaundersonTable class that is responsible to sample if
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// it was no, single, few or multiple scattering case and delivers the
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// angular deflection (i.e. cos(theta) and sin(theta)).
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// Two screening options are provided:
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// - if fgIsUsePWATotalXsecData=TRUE i.e. SetOptionPWAScreening(TRUE)
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// was called before initialisation: screening parameter value A is
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// determined such that the first transport coefficient G1(A)
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// computed according to the screened Rutherford DCS for elastic
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// scattering will reproduce the one computed from the PWA elastic
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// and first transport mean free paths[4].
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// - if fgIsUsePWATotalXsecData=FALSE i.e. default value or
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// SetOptionPWAScreening(FALSE) was called before initialisation:
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// screening parameter value A is computed according to Moliere's
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// formula (by using material dependent parameters \chi_cc2 and b_c
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// precomputed for each material used at initialization in
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// G4GoudsmitSaundersonTable) [3]
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// Elastic and first trasport mean free paths are used consistently.
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// The new version is self-consistent, several times faster, more
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// robust and accurate compared to the earlier version.
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// Spin effects as well as a more accurate energy loss correction and
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// computations of Lewis moments will be implemented later on.
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// [1] A.F.Bielajew, NIMB 111 (1996) 195-208
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// [2] I.Kawrakow, A.F.Bielajew, NIMB 134(1998) 325-336
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// [3] I.Kawrakow, E.Mainegra-Hing, D.W.O.Rogers, F.Tessier,B.R.B.Walters,
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// NRCC Report PIRS-701 (2013)
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// [4] F.Salvat, A.Jablonski, C.J. Powell, CPC 165(2005) 157-190
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// 02.09.2015 M. Novak: first version of new step limit is provided.
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// fUseSafetyPlus corresponds to Urban fUseSafety (default)
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// fUseDistanceToBoundary corresponds to Urban fUseDistanceToBoundary
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// fUseSafety corresponds to EGSnrc error-free stepping algorithm
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// Range factor can be significantly higher at each case than in Urban.
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// 23.08.2017 M. Novak: added corrections to account spin effects (Mott-correction).
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// It can be activated by setting the fIsMottCorrection flag to be true
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// before initialization using the SetOptionMottCorrection() public method.
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// The fMottCorrection member is responsible to handle pre-computed Mott
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// correction (rejection) functions obtained by numerically computing
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// Goudsmit-Saunderson agnular distributions based on a DCS accounting spin
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// effects and screening corrections. The DCS used to compute the accurate
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// GS angular distributions is: DCS_{cor} = DCS_{SR}x[ DCS_{R}/DCS_{Mott}] where :
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// # DCS_{SR} is the relativistic Screened-Rutherford DCS (first Born approximate
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// solution of the Klein-Gordon i.e. relativistic Schrodinger equation =>
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// scattering of spinless e- on exponentially screened Coulomb potential)
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// note: the default (without using Mott-correction) GS angular distributions
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// are based on this DCS_{SR} with Moliere's screening parameter!
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// # DCS_{R} is the Rutherford DCS which is the same as above but without
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// screening
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// # DCS_{Mott} is the Mott DCS i.e. solution of the Dirac equation with a bare
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// Coulomb potential i.e. scattering of particles with spin (e- or e+) on a
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// point-like unscreened Coulomb potential
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// # moreover, the screening parameter of the DCS_{cor} was determined such that
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// the DCS_{cor} with this corrected screening parameter reproduce the first
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// transport cross sections obtained from the corresponding most accurate DCS
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// (i.e. from elsepa [4])
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// Unlike the default GS, the Mott-corrected angular distributions are particle type
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// (different for e- and e+ <= the DCS_{Mott} and the screening correction) and target
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// (Z and material) dependent.
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// 02.02.2018 M. Novak: implemented CrossSectionPerVolume interface method (used only for testing)
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// 26.10.2025 M. Novak: the model has only its accurate stepping and boundary crossing algorithms
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// left as the only option that ensures the expected precision, especially when activating
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// its Mott correction option (that also activates the screeing and scattering power
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// corrections). The model has been used for describing e-/e+ MSC (below 100 MeV kinetic)
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// energy in the option4, Penelope and Livermore EM physics constructors since Geant4 10.6.
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//
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//
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// Class description:
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// Kawrakow-Bielajew Goudsmit-Saunderson MSC model based on the screened Rutherford DCS
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// for elastic scattering of e-/e+. Option, to include Mott correction, is also available
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// that also activates the screening and scattering power corrections leading to the most
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// precise settings of the model. With the accurate electron stepping and boundary crossing
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// algorithm the model provides very precise e-/e+ simulation and tracking independently
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// from the target material and geometrical configurations similarly to EGSnrc. All details
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// are available in the corresponding technical note (M. Novak: https://arxiv.org/abs/2410.13361).
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//
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// References:
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// M. Novak: https://arxiv.org/abs/2410.13361
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//
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// -----------------------------------------------------------------------------
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#ifndef G4GoudsmitSaundersonMscModel_h
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#define G4GoudsmitSaundersonMscModel_h 1
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#include <CLHEP/Units/SystemOfUnits.h>
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#include "G4VMscModel.hh"
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#include "G4PhysicsTable.hh"
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#include "G4MaterialCutsCouple.hh"
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#include "globals.hh"
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class G4DataVector;
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class G4ParticleChangeForMSC;
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class G4LossTableManager;
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class G4GoudsmitSaundersonTable;
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class G4GSPWACorrections;
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class G4GoudsmitSaundersonMscModel : public G4VMscModel
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{
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public:
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G4GoudsmitSaundersonMscModel(const G4String& nam = "GoudsmitSaunderson");
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~G4GoudsmitSaundersonMscModel() override;
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void Initialise(const G4ParticleDefinition*, const G4DataVector&) override;
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void InitialiseLocal(const G4ParticleDefinition* p, G4VEmModel* masterModel) override;
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G4ThreeVector& SampleScattering(const G4ThreeVector&, G4double safety) override;
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G4double ComputeTruePathLengthLimit(const G4Track& track, G4double& currentMinimalStep) override;
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G4double ComputeGeomPathLength(G4double truePathLength) override;
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G4double ComputeTrueStepLength(G4double geomStepLength) override;
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// method to compute first transport cross section per Volume (i.e. macroscropic first transport cross section; this
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// method is used only for testing and not during a normal simulation)
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G4double CrossSectionPerVolume(const G4Material*, const G4ParticleDefinition*, G4double kineticEnergy, G4double cutEnergy = 0.0, G4double maxEnergy = DBL_MAX) override;
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void StartTracking(G4Track*) override;
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void SampleMSC();
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G4double GetTransportMeanFreePath(const G4ParticleDefinition*, G4double);
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void SetOptionPWACorrection(G4bool opt) { fIsUsePWACorrection = opt; }
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G4bool GetOptionPWACorrection() const { return fIsUsePWACorrection; }
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void SetOptionMottCorrection(G4bool opt) { fIsUseMottCorrection = opt; }
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G4bool GetOptionMottCorrection() const { return fIsUseMottCorrection; }
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void SetOptionOptimisation(G4bool opt) { fIsUseOptimisation = opt; }
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G4bool GetOptionOptimisation() const { return fIsUseOptimisation; }
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G4GoudsmitSaundersonTable* GetGSTable() { return fGSTable; }
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G4GSPWACorrections* GetPWACorrection() { return fPWACorrection; }
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// hide assignment operator
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G4GoudsmitSaundersonMscModel & operator=(const G4GoudsmitSaundersonMscModel &right) = delete;
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G4GoudsmitSaundersonMscModel(const G4GoudsmitSaundersonMscModel&) = delete;
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private:
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inline void SetParticle(const G4ParticleDefinition* p);
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inline G4double GetLambda(G4double);
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G4double GetTransportMeanFreePathOnly(const G4ParticleDefinition*,G4double);
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private:
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G4double currentKinEnergy;
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G4double currentRange;
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G4double presafety;
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G4int currentMaterialIndex;
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//
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const G4ParticleDefinition* particle;
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G4ParticleChangeForMSC* fParticleChange;
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const G4MaterialCutsCouple* currentCouple;
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G4GoudsmitSaundersonTable* fGSTable;
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G4GSPWACorrections* fPWACorrection;
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G4bool fIsUsePWACorrection;
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G4bool fIsUseMottCorrection;
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G4bool fIsUseOptimisation;
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//
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G4double fLambda0; // elastic mean free path
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G4double fLambda1; // first transport mean free path
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G4double fScrA; // screening parameter
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G4double fG1; // first transport coef.
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// in case of Mott-correction
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G4double fMCtoScrA;
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G4double fMCtoQ1;
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G4double fMCtoG2PerG1;
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//
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G4double fTheTrueStepLenght;
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G4double fTheZPathLenght;
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//
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G4ThreeVector fTheDisplacementVector;
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G4ThreeVector fTheNewDirection;
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//
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G4bool fIsEndedUpOnBoundary;
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G4bool fIsMultipleScattering;
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G4bool fIsSingleScattering;
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G4bool fIsNoScatteringInMSC;
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G4bool fIsSimplified;
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};
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////////////////////////////////////////////////////////////////////////////////
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inline
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void G4GoudsmitSaundersonMscModel::SetParticle(const G4ParticleDefinition* p)
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{
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if (p != particle) {
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particle = p;
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}
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}
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#endif
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