| Geant4 Cross Reference |
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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 "G4fissionEvent.hh"
60
61 G4double G4fissionEvent::G4SmpNVel(G4double eng, G4double* cosdiru, G4double* cosdirv, G4double* cosdirw) {
62
63 /*
64 Description
65 Knowing the neutron energy, determine its velocity and the 3 direction cosines
66 */
67
68 /*
69 Input
70 eng - energy of neutron
71 Output
72 - velocity
73 - 3 components of the neutron velocity
74 in arguments (cosdiru, cosdirv, cosdirw)
75 */
76
77 const G4double rme = 939.56563; /* Rest Mass Energy equivalents for neutrons (MeV) */
78 const G4double cspeed = 2.99792458e+8; /* speed of light (m/sec) */
79
80 G4double vel;
81 G4double ratio = eng/rme;
82
83 if (ratio > 1.e-8) {
84 /* Relativistic vel calculation */
85 vel = cspeed*std::sqrt(1.-rme*rme/((rme+eng)*(rme+eng)));
86 } else {
87 /* Non-relativistic vel calculation */
88 vel = cspeed*std::sqrt(2.*eng/rme);
89 }
90
91 G4SmpIsoDir(cosdiru, cosdirv, cosdirw);
92
93 return vel;
94 }
95