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51 // Copyright (c) 2006 The Regents of the University of California.
52 // All rights reserved.
53 // UCRL-CODE-224807
54 //
55 //
56 //
57
58 #include <cmath>
59 #include "G4Exp.hh"
60 #include "G4Log.hh"
61 #include "G4fissionEvent.hh"
62
63 #define TWOPI 6.283185307
64 #define SQRT2 1.414213562
65 #define BSHIFT -0.43287
66 #define WIDTH 1.079
67
68 G4double G4fissionEvent::G4SmpTerrell(G4double nubar) {
69 /*
70 Description
71 Sample Fission Number from Terrell's modified Gaussian distribution
72
73 method uses Red Cullen's algoritm UCRL-TR-222526
74 */
75
76 /*
77 Input
78 nubar - average number of neutrons per fission
79 Output
80 G4SmpTerrell - sampled multiplicity
81
82 */
83
84 G4double width;
85 G4double temp1, temp2, expo, cshift;
86 G4double rw, theta, sampleg;
87
88
89 if (nubar < WIDTH) {
90 std::ostringstream o;
91 o << nubar;
92 const std::string& errMsg = "fission nubar out of range, nubar=" + o.str();
93 G4fissionerr(6, "SmpTerrell", errMsg);
94 }
95
96 width = SQRT2 * WIDTH;
97 temp1 = nubar + 0.5;
98 temp2 = temp1/width;
99 temp2 *= temp2;
100 expo = G4Exp(-temp2);
101 cshift = temp1 + BSHIFT * WIDTH * expo/(1. - expo);
102
103 G4int icounter = 0;
104 G4int icounter_max = 1024;
105 do {
106 rw = std::sqrt(-G4Log(fisslibrng()));
107 theta = TWOPI * fisslibrng();
108 sampleg = width * rw * std::cos(theta) + cshift;
109 icounter++;
110 if ( icounter > icounter_max ) {
111 G4cout << "Loop-counter exceeded the threshold value at " << __LINE__ << "th line of " << __FILE__ << "." << G4endl;
112 break;
113 }
114 } while (sampleg < 0.0);
115 // Loop checking, 11.03.2015, T. Koi
116
117 return std::floor(sampleg);
118 }
119