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25 //
26 //
27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class header file
30 //
31 //
32 // File name: G4eDPWAElasticDCS
33 //
34 // Author: Mihaly Novak
35 //
36 // Creation date: 02.07.2020
37 //
38 // Modifications:
39 //
40 // Class Description:
41 //
42 // Contains numerical Differential Cross Sections (DCS) for e-/e+ Coulomb
43 // scattering computed by Dirac Partial Wave Analysis (DPWA) [1]:
44 // - electrostatic interaction, with a local exchange correction in the case of
45 // electrons (using Dirac-Fock e- densities; finite nuclear size with Fermi
46 // charge distribution; exchange potential with Furness and McCarthy for e-)[2]
47 // - correlation-polarization (projectiles cause the polarization of the charge
48 // cloud of the target atom and the induced dipole moment acts back on the
49 // projectile) was accounted by using Local-Density Approximation (LDA) [2]
50 // - absorption: not included since it's an inelastic channel [2] (the cor-
51 // responding excitations needs to be modelled by a separate, independent,
52 // inelastic model).
53 // Using the above mentioned DPWA computation with a free atom approximation
54 // might lead to questionable results below few hundred [eV] where possible
55 // solid state or bounding effects might start to affect the potential.
56 // Nevertheless, the lower energy was set to 10 eV in order to provide(at least)
57 // some model even at low energies (with this caution). The highest projectile
58 // kinetic energy is 100 [MeV].
59 //
60 // The class provides interface methods for elastic, first-, second-transport
61 // cross section computations as well as for sampling cosine of polar angular
62 // deflections. These interface methods are also available for resricted cross
63 // section computations and angular deflection sampling.
64 //
65 // References:
66 //
67 // [1] Salvat, F., Jablonski, A. and Powell, C.J., 2005. ELSEPA—Dirac partial-
68 // wave calculation of elastic scattering of electrons and positrons by
69 // atoms, positive ions and molecules. Computer physics communications,
70 // 165(2), pp.157-190.
71 // [2] Salvat, F., 2003. Optical-model potential for electron and positron
72 // elastic scattering by atoms. Physical Review A, 68(1), p.012708.
73 // [3] Benedito, E., Fernández-Varea, J.M. and Salvat, F.,2001. Mixed simulation
74 // of the multiple elastic scattering of electrons and positrons using
75 // partial-wave differential cross-sections. Nuclear Instruments and Methods
76 // in Physics Research Section B: Beam Interactions with Materials and Atoms,
77 // 174(1-2), pp.91-110.
78 //
79 // -------------------------------------------------------------------
80
81 #ifndef G4eDPWAElasticDCS_h
82 #define G4eDPWAElasticDCS_h 1
83
84
85 #include <vector>
86 #include <fstream>
87 #include <iomanip>
88 #include <sstream>
89
90 #include "globals.hh"
91 #include "G4String.hh"
92 #include "G4Physics2DVector.hh"
93
94
95 #include "G4MaterialTable.hh"
96 #include "G4Material.hh"
97 #include "G4Element.hh"
98 #include "G4MaterialCutsCouple.hh"
99 #include "G4ProductionCutsTable.hh"
100
101
102 #include "G4Log.hh"
103 #include "G4Exp.hh"
104
105
106 class G4eDPWAElasticDCS {
107
108 public:
109
110 // CTR:
111 // - iselectron : data for e- (for e+ otherwise)
112 // - isrestricted : sampling of angular deflection on restricted interavl is
113 // required (i.e. in case of mixed-simulation models)
114 G4eDPWAElasticDCS(G4bool iselectron=true, G4bool isrestricted=false);
115
116 // DTR
117 ~G4eDPWAElasticDCS();
118
119 // initialise for a given 'iz' atomic number:
120 // - nothing happens if it has already been initialised for that Z.
121 void InitialiseForZ(std::size_t iz);
122
123 // Computes the elastic, first and second cross sections for the given kinetic
124 // energy and target atom.
125 // Cross sections are zero ff ekin is below/above the kinetic energy grid
126 void ComputeCSPerAtom(G4int iz, G4double ekin, G4double& elcs, G4double& tr1cs,
127 G4double& tr2cs, G4double mumin=0.0, G4double mumax=1.0);
128
129
130 // samples cos(theta) i.e. cosine of the polar angle of scattering in elastic
131 // interaction (Coulomb scattering) of the projectile (e- or e+ depending on
132 // fIsElectron) with kinetic energy of exp('lekin'), target atom with atomic
133 // muber of 'iz'. See the 'SampleCosineThetaRestricted' for obtain samples on
134 // a restricted inteval.
135 G4double SampleCosineTheta(std::size_t iz, G4double lekin, G4double r1,
136 G4double r2, G4double r3);
137
138 // samples cos(theta) i.e. cosine of the polar angle of scattering in elastic
139 // interaction (Coulomb scattering) of the projectile (e- or e+ depending on
140 // fIsElectron) with kinetic energy of exp('lekin'), target atom with atomic
141 // muber of 'iz'.
142 // The cosine theta will be in the [costMin, costMax] interval where costMin
143 // corresponds to a maximum allowed polar scattering angle thetaMax while
144 // costMin corresponds to minimum allowed polar scatterin angle thetaMin.
145 // See the 'SampleCosineTheta' for obtain samples on the entire [-1,1] range.
146 G4double SampleCosineThetaRestricted(std::size_t iz, G4double lekin,
147 G4double r1, G4double r2,
148 G4double costMax, G4double costMin);
149
150 // interpolate scattering power correction form table buit at init.
151 G4double ComputeScatteringPowerCorrection(const G4MaterialCutsCouple *matcut,
152 G4double ekin);
153
154 // build scattering power correction table at init.
155 void InitSCPCorrection(G4double lowEnergyLimit, G4double highEnergyLimit);
156
157
158 private:
159
160 // data structure to store one sampling table: combined Alias + RatIn
161 // NOTE: when Alias is used, sampling on a resctricted interval is not possible
162 // However, Alias makes possible faster sampling. Alias is used in case
163 // of single scattering model while it's not used in case of mixed-model
164 // when restricted interval sampling is needed. This is controlled by
165 // the fIsRestrictedSamplingRequired flag (false by default).
166 struct OneSamplingTable {
167 OneSamplingTable () = default;
168 void SetSize(std::size_t nx, G4bool useAlias) {
169 fN = nx;
170 // Alias
171 if (useAlias) {
172 fW.resize(nx);
173 fI.resize(nx);
174 }
175 // Ratin
176 fCum.resize(nx);
177 fA.resize(nx);
178 fB.resize(nx);
179 }
180
181 // members
182 std::size_t fN; // # data points
183 G4double fScreenParA; // the screening parameter
184 std::vector<G4double> fW;
185 std::vector<G4double> fCum;
186 std::vector<G4double> fA;
187 std::vector<G4double> fB;
188 std::vector<G4int> fI;
189 };
190
191
192 // loads the kinetic energy and theta grids for the DCS data (first init step)
193 // should be called only by the master
194 void LoadGrid();
195
196 // load DCS data for a given Z
197 void LoadDCSForZ(G4int iz);
198
199 // loads sampling table for the given Z over the enrgy grid
200 void BuildSmplingTableForZ(G4int iz);
201
202 G4double SampleMu(std::size_t izet, std::size_t ie, G4double r1, G4double r2);
203
204 G4double FindCumValue(G4double u, const OneSamplingTable& stable,
205 const std::vector<G4double>& uvect);
206
207 // muMin and muMax : no checks on these
208 G4double SampleMu(std::size_t izet, std::size_t ie, G4double r1, G4double muMin,
209 G4double muMax);
210
211 // set the DCS data directory path
212 const G4String& FindDirectoryPath();
213
214 // uncompress one data file into the input string stream
215 void ReadCompressedFile(G4String fname, std::istringstream &iss);
216
217 // compute Molier material dependent parameters
218 void ComputeMParams(const G4Material* mat, G4double& theBc, G4double& theXc2);
219
220
221 // members
222 private:
223
224 // indicates if the object is for mixed-simulation (single scatterin otherwise)
225 G4bool fIsRestrictedSamplingRequired;
226 // indicates if the object is for e- (for e+ otherwise)
227 G4bool fIsElectron;
228 // indicates if the ekin, mu grids has already been loaded (only once)
229 static G4bool gIsGridLoaded;
230 // data directory
231 static G4String gDataDirectory;
232 // max atomic number (Z) for which DCS has been computed (103)
233 static constexpr std::size_t gMaxZ = 103;
234 // energy and theta grid(s) relaed variables: loaded from gridinfo by LoadGrid
235 static std::size_t gNumEnergies;
236 static std::size_t gIndxEnergyLim;// the energy index just above 2 [keV]
237 static std::size_t gNumThetas1; // used for e- below 2 [keV]
238 static std::size_t gNumThetas2; // used for e+ and for e- bove 2 [keV]
239 static std::vector<G4double> gTheEnergies; // log-kinetic energy grid
240 static std::vector<G4double> gTheMus1; // mu(theta) = 0.5[1-cos(theta)]
241 static std::vector<G4double> gTheMus2;
242 static std::vector<G4double> gTheU1; // u(mu; A'=0.01) = (A'+1)mu/(mu+A')
243 static std::vector<G4double> gTheU2;
244 static G4double gLogMinEkin; // log(gTheEnergies[0])
245 static G4double gInvDelLogEkin;// 1./log(gTheEnergies[i+1]/gTheEnergies[i])
246 // abscissas and weights of an 8 point Gauss-Legendre quadrature
247 // for numerical integration on [0,1]
248 static const G4double gXGL[8];
249 static const G4double gWGL[8];
250 //
251 std::vector<G4Physics2DVector*> fDCS; // log(DCS) data per Z
252 std::vector<G4Physics2DVector*> fDCSLow; // only for e- E < 2keV
253 // sampling tables: only one of the followings will be utilized
254 std::vector< std::vector<OneSamplingTable>* > fSamplingTables;
255 //
256 // scattering power correction: to account sub-threshold inelastic deflections
257 const G4int fNumSPCEbinPerDec = 3;
258 struct SCPCorrection {
259 G4bool fIsUse; //
260 G4double fPrCut; // sec. e- production cut energy
261 G4double fLEmin; // log min energy
262 G4double fILDel; // inverse log delta kinetic energy
263 std::vector<G4double> fVSCPC; // scattering power correction vector
264 };
265 std::vector<SCPCorrection*> fSCPCPerMatCuts;
266
267
268 };
269
270 #endif
271