Geant4  10.02.p02
G4E1Probability.cc
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26 // $Id: G4E1Probability.cc 92144 2015-08-19 14:25:18Z gcosmo $
27 //
28 //---------------------------------------------------------------------
29 //
30 // Geant4 class G4E1Probability
31 //
32 // by V. Lara (May 2003)
33 //
34 // Modifications:
35 // 18.05.2010 V.Ivanchenko trying to speedup the most slow method
36 // by usage of G4Pow, integer A and introduction of const members
37 // 17.11.2010 V.Ivanchenko perform general cleanup and simplification
38 // of integration method; low-limit of integration is defined
39 // by gamma energy or is zero (was always zero before)
40 //
41 
42 #include "G4E1Probability.hh"
43 #include "Randomize.hh"
44 #include "G4Pow.hh"
45 #include "G4Exp.hh"
46 #include "G4SystemOfUnits.hh"
47 
48 static const G4double tolerance = 0.1*CLHEP::keV;
49 
51 {
52  G4double x = CLHEP::pi*CLHEP::hbarc;
53  normC = 1.0 / (x*x);
56  Afrag = 0;
58 }
59 
61 {}
62 
63 
65  G4double gammaE)
66 {
67  // Calculate the probability density here
68 
69  // From nuclear fragment properties and the excitation energy, calculate
70  // the probability density for photon evaporation from U to U - gammaE
71  // (U = nucleus excitation energy, gammaE = total evaporated photon
72  // energy). Fragment = nuclear fragment BEFORE de-excitation
73 
74  G4double theProb = 0.0;
75 
76  if(gammaE > tolerance) {
77 
78  G4double Uexcite = frag.GetExcitationEnergy();
79  G4double U = std::max(0.0, Uexcite - gammaE);
80 
81  // Need a level density parameter.
82  // For now, just use the constant approximation (not reliable near magic
83  // nuclei) - is equivalent to G4ConstantLevelDensityParameter class
84 
85  if(Afrag != frag.GetA_asInt()) {
86  Afrag = frag.GetA_asInt();
88 
89  // Define constants for the photoabsorption cross-section (the reverse
90  // process of our de-excitation)
91  sigma0 = 2.5 * Afrag * millibarn;
92  Egdp = (40.3 / fG4pow->powZ(Afrag,0.2) )*MeV;
93  GammaR = 0.30 * Egdp;
94  }
95  // VI reduce number of calls to exp
96  G4double levelDens =
97  G4Exp(2*(std::sqrt(aLevelDensityParam*U)-
98  std::sqrt(aLevelDensityParam*Uexcite)));
99 
100  //G4cout<<" Uexcite, gammaE = "<<Uexcite<<" "<<gammaE<<G4endl;
101  //cout<<" lev density param = "<<aLevelDensityParam<<G4endl;
102  //cout<<" level densities = "<<levelDensBef<<" "<<levelDensAft<<G4endl;
103  //cout<<" sigma0 = "<<sigma0<<G4endl;
104  //cout<<" Egdp, GammaR = "<<Egdp<<" "<<GammaR<<G4endl;
105  //cout<<" normC = "<<normC<<G4endl;
106 
107  // VI implementation 18.05.2010
108  G4double gammaE2 = gammaE*gammaE;
109  G4double gammaR2 = gammaE2*GammaR*GammaR;
110  G4double egdp2 = gammaE2 - Egdp*Egdp;
111  G4double sigmaAbs = sigma0*gammaR2/(egdp2*egdp2 + gammaR2);
112  theProb = normC * sigmaAbs * gammaE2 * levelDens;
113 
114  //G4cout<<" sigmaAbs = "<<sigmaAbs <<" Probability = "<<theProb<<G4endl;
115  }
116  return theProb;
117 }
118 
120  G4double gammaE)
121 {
122  // From nuclear fragment properties and the excitation energy, calculate
123  // the probability for photon evaporation down to last ground level.
124  // fragment = nuclear fragment BEFORE de-excitation
125 
126  G4double upperLim = gammaE;
127  G4double lowerLim = 0.0;
128 
129  //G4cout << "G4E1Probability::EmissionProbability: Emin= " << lowerLim
130  // << " Emax= " << upperLim << G4endl;
131  if( upperLim - lowerLim <= tolerance) { return 0.0; }
132 
133  // Need to integrate EmissionProbDensity from lowerLim to upperLim
134  // and multiply by factor 3 (?!)
135 
136  G4double integ = EmissionIntegration(frag,lowerLim,upperLim);
137  return integ;
138 }
139 
141  G4double lowLim, G4double upLim)
142 
143 {
144  // Simple integration
145  // VI replace by direct integration over 100 point
146 
147  static const G4int numIters = 100;
148  G4double Step = (upLim-lowLim)/G4double(numIters);
149 
150  G4double res = 0.0;
151  G4double x = lowLim - 0.5*Step;
152 
153  for(G4int i = 0; i < numIters; ++i) {
154  x += Step;
155  res += EmissionProbDensity(frag, x);
156  }
157 
158  if(res > 0.0) { res *= Step; }
159  else { res = 0.0; }
160 
161  return res;
162 
163 }
164 
165 
static G4Pow * GetInstance()
Definition: G4Pow.cc:55
static const double MeV
Definition: G4SIunits.hh:211
G4double aLevelDensityParam
G4double EmissionProbability(const G4Fragment &frag, G4double excite)
G4double EmissionProbDensity(const G4Fragment &frag, G4double ePhoton)
int G4int
Definition: G4Types.hh:78
G4int GetA_asInt() const
Definition: G4Fragment.hh:256
G4double theLevelDensityPerNucleon
static const G4double tolerance
G4double G4Exp(G4double initial_x)
Exponential Function double precision.
Definition: G4Exp.hh:183
static const double pi
Definition: G4SIunits.hh:74
T max(const T t1, const T t2)
brief Return the largest of the two arguments
virtual ~G4E1Probability()
const G4double x[NPOINTSGL]
G4double EmissionIntegration(const G4Fragment &frag, G4double lowLim, G4double upLim)
static const double millibarn
Definition: G4SIunits.hh:105
Definition: Step.hh:41
static const double keV
Definition: G4SIunits.hh:213
G4double powZ(G4int Z, G4double y) const
Definition: G4Pow.hh:254
double G4double
Definition: G4Types.hh:76
G4double GetExcitationEnergy() const
Definition: G4Fragment.hh:273