Geant4  v4-10.4-release
G4SmpNVel.cc
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51 // Copyright (c) 2006 The Regents of the University of California.
53 // UCRL-CODE-224807
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56 // $Id: G4SmpNVel.cc 67966 2013-03-13 09:38:38Z gcosmo$
57 //
58
59 #include <cmath>
60 #include "G4fissionEvent.hh"
61
63
64 /*
65  Description
66  Knowing the neutron energy, determine its velocity and the 3 direction cosines
67 */
68
69 /*
70  Input
71  eng - energy of neutron
72  Output
73  - velocity
74  - 3 components of the neutron velocity
75  in arguments (cosdiru, cosdirv, cosdirw)
76 */
77
78  const G4double rme = 939.56563; /* Rest Mass Energy equivalents for neutrons (MeV) */
79  const G4double cspeed = 2.99792458e+8; /* speed of light (m/sec) */
80
81  G4double vel;
82  G4double ratio = eng/rme;
83
84  if (ratio > 1.e-8) {
85 /* Relativistic vel calculation */
86  vel = cspeed*std::sqrt(1.-rme*rme/((rme+eng)*(rme+eng)));
87  } else {
88 /* Non-relativistic vel calculation */
89  vel = cspeed*std::sqrt(2.*eng/rme);
90  }
91
92  G4SmpIsoDir(cosdiru, cosdirv, cosdirw);
93
94  return vel;
95 }
void G4SmpIsoDir(G4double *cosdiru, G4double *cosdirv, G4double *cosdirw)
Definition: G4SmpIsoDir.cc:64
double G4double
Definition: G4Types.hh:76
G4double G4SmpNVel(G4double eng, G4double *cosdiru, G4double *cosdirv, G4double *cosdirw)
Definition: G4SmpNVel.cc:62