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25 //
26 //
27 // ----------------------------------------------------------------------------
28 //
29 // GEANT4 Class header file
30 //
31 // File name: G4GSMottCorrection
32 //
33 // Author: Mihaly Novak
34 //
35 // Creation date: 23.08.2017
36 //
37 // Modifications:
38 //
39 // Class description:
40 // An object of this calss is used in the G4GoudsmitSaundersonTable when Mott-correction
41 // was required by the user in the G4GoudsmitSaundersonMscModel.
42 // The class is responsible to handle pre-computed Mott correction (rejection) functions
43 // obtained as a ratio of GS angular distributions computed based on the Screened-Rutherford
44 // DCS to GS angular distributions computed based on a more accurate corrected DCS_{cor}.
45 // The DCS used to compute the accurate Goudsmit-Saunderson angular distributions is [1]:
46 // DCS_{cor} = DCS_{SR}x[ DCS_{R}/DCS_{Mott}] where :
47 // # DCS_{SR} is the relativistic Screened-Rutherford DCS (first Born approximate
48 // solution of the Klein-Gordon i.e. relativistic Schrodinger equation =>
49 // scattering of spinless e- on exponentially screened Coulomb potential)
50 // note: the default (without using Mott-correction) GS angular distributions
51 // are based on this DCS_{SR} with Moliere's screening parameter!
52 // # DCS_{R} is the Rutherford DCS which is the same as above but without
53 // screening
54 // # DCS_{Mott} is the Mott DCS i.e. solution of the Dirac equation with a bare
55 // Coulomb potential i.e. scattering of particles with spin (e- or e+) on a
56 // point-like unscreened Coulomb potential [2]
57 // # moreover, the screening parameter of the DCS_{cor} was determined such that
58 // the DCS_{cor} with this corrected screening parameter reproduce the first
59 // transport cross sections obtained from the corresponding most accurate DCS [3].
60 // Unlike the default GS, the Mott-corrected angular distributions are particle type
61 // (different for e- and e+ <= the DCS_{Mott} and the screening correction) and target
62 // (Z and material) dependent.
63 //
64 // References:
65 // [2] I.Kawrakow, E.Mainegra-Hing, D.W.O.Rogers, F.Tessier,B.R.B.Walters, NRCC
66 // Report PIRS-701 (2013)
67 // [2] N.F. Mott, Proc. Roy. Soc. (London) A 124 (1929) 425.
68 // [3] F.Salvat, A.Jablonski, C.J. Powell, CPC 165(2005) 157-190
69 //
70 // -----------------------------------------------------------------------------
71
72 #ifndef G4GSMottCorrection_h
73 #define G4GSMottCorrection_h 1
74
75 #include <CLHEP/Units/SystemOfUnits.h>
76
77 #include "globals.hh"
78
79 #include <vector>
80 #include <string>
81 #include <sstream>
82
83 class G4Material;
84 class G4Element;
85
86
87 class G4GSMottCorrection {
88 public:
89 G4GSMottCorrection(G4bool iselectron=true);
90
91 ~G4GSMottCorrection();
92
93 void Initialise();
94
95 void GetMottCorrectionFactors(G4double logekin, G4double beta2, G4int matindx,
96 G4double &mcToScr, G4double &mcToQ1, G4double &mcToG2PerG1);
97
98 G4double GetMottRejectionValue(G4double logekin, G4double G4beta2, G4double q1, G4double cost,
99 G4int matindx, G4int &ekindx, G4int &deltindx);
100
101 static G4int GetMaxZet() { return gMaxZet; }
102
103 private:
104 void InitMCDataPerElement();
105
106 void InitMCDataPerMaterials();
107
108 void LoadMCDataElement(const G4Element*);
109
110 void ReadCompressedFile(const std::string& fname, std::istringstream &iss);
111
112 void InitMCDataMaterial(const G4Material*);
113 //
114 // dat structures
115 struct DataPerDelta {
116 G4double fSA; // a,b,c,d spline interpolation parameters for the last \sin(0.5\theta) bin
117 G4double fSB;
118 G4double fSC;
119 G4double fSD;
120 G4double *fRejFuntion; // rejection func. for a given E_{kin}, \delta, e^-/e^+ over the \sin(0.5\theta) grid
121 };
122
123 struct DataPerEkin {
124 G4double fMCScreening; // correction factor to Moliere screening parameter
125 G4double fMCFirstMoment; // correction factor to first moment
126 G4double fMCSecondMoment; // correction factor to second
127 DataPerDelta **fDataPerDelta; // per delta value data structure for each delta values
128 };
129
130 // either per material or per Z
131 struct DataPerMaterial {
132 DataPerEkin **fDataPerEkin; // per kinetic energy data structure for each kinetic energy value
133 };
134 //
135 void AllocateDataPerMaterial(DataPerMaterial*);
136 void DeAllocateDataPerMaterial(DataPerMaterial*);
137 void ClearMCDataPerElement();
138 void ClearMCDataPerMaterial();
139 //
140 // data members:
141 // - Mott correction data are computed over a :
142 // I. Kinetic energy grid [both rejection functions and correction factors]:
143 // 1. kinetic energy grid from 1[keV] - 100[keV] with log-spacing 16 points:
144 // # linear interpolation on \ln[E_{kin}] will be used
145 // 2. \beta^2 grid from E_{kin} = 100[keV](~0.300546) - \beta^2=0.9999(~50.5889MeV]) with linear spacing 16 points:
146 // # linear interpolation on \beta^2 will be used
147 // 3. the overall kinetic energy grid is from E_{kin}=1[keV] - E_{kin}<=\beta^2=0.9999(~50.5889MeV]) with 31 points
148 // II. Delta value grid [rejection functions at a given kinetic energy(also depends on \theta;Z,e-/e+)]:
149 // 1. \delta=2 Q_{1SR} (\eta_{MCcor})/ [1-2 Q_{1SR} (\eta_{MCcor})] where Q_{1SR} is the first moment i.e.
150 // Q_{1SR}(\eta_{MCcor}) =s/\lambda_{el}G_{1SR}(\eta_{MCcor}) where s/\lambda_{el} is the mean number of elastic
151 // scattering along the path s and G_{1SR}(\eta_{MCcor}) is the first, Screened-Rutherford transport coefficient
152 // but computed by using the Mott-corrected Moliere screening parameter
153 // 2. the delta value grid is from [0(1e-3) - 0.9] with linear spacing of 28 points:
154 // # linear interpolation will be used on \delta
155 // III. \sin(0.5\theta) grid[rejection function at a given kinetic energy - delta value pair (also depends on Z,e-/e+)]:
156 // 1. 32 \sin(0.5\theta) pints between [0,1] with linear spacing: # linear interpolation on \sin(0.5\theta) will
157 // be used exept the last bin where spline is used (the corresponding 4 spline parameters are also stored)
158 private:
159 G4bool fIsElectron;
160 static constexpr G4int gNumEkin = 31; // number of kinetic energy grid points for Mott correction
161 static constexpr G4int gNumBeta2 = 16; // \beta^2 values between [fMinBeta2-fMaxBeta2]
162 static constexpr G4int gNumDelta = 28; // \delta values between [0(1.e-3)-0.9]
163 static constexpr G4int gNumAngle = 32; //
164 static constexpr G4int gMaxZet = 98; // max. Z for which Mott-correction data were computed (98)
165 static constexpr G4double gMinEkin = 1.*CLHEP::keV; // minimum kinetic energy value
166 static constexpr G4double gMidEkin = 100.*CLHEP::keV; // kinetic energy at the border of the E_{kin}-\beta^2 grids
167 static constexpr G4double gMaxBeta2 = 0.9999; // maximum \beta^2 value
168 static constexpr G4double gMaxDelta = 0.9; // maximum \delta value (the minimum is 0(1.e-3))
169 //
170 G4double fMaxEkin; // from max fMaxBeta2 = 0.9999 (~50.5889 [MeV])
171 G4double fLogMinEkin; // \ln[fMinEkin]
172 G4double fInvLogDelEkin; // 1/[\ln(fMidEkin/fMinEkin)/(fNumEkin-fNumBeta2)]
173 G4double fMinBeta2; // <= E_{kin}=100 [keV] (~0.300546)
174 G4double fInvDelBeta2; // 1/[(fMaxBeta2-fMinBeta2)/(fNumBeta2-1)]
175 G4double fInvDelDelta; // 1/[0.9/(fNumDelta-1)]
176 G4double fInvDelAngle; // 1/[(1-0)/fNumAngle-1]
177 //
178 static const std::string gElemSymbols[];
179 //
180 std::vector<DataPerMaterial*> fMCDataPerElement; // size will be gMaxZet+1; won't be null only at used Z indices
181 std::vector<DataPerMaterial*> fMCDataPerMaterial; // size will #materials; won't be null only at used mat. indices
182 };
183
184 #endif // G4GSMottCorrection_h
185