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Remove special treatment of mu for fission

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This commit is contained in:
Paul Romano 2020-11-13 13:28:32 -06:00
parent 4399645859
commit 7ef73f048d
4 changed files with 8 additions and 39 deletions
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19
src/physics.cpp
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@ -1009,24 +1009,13 @@ sample_cxs_target_velocity(double awr, double E, Direction u, double kT, uint64_
void sample_fission_neutron(int i_nuclide, const Reaction& rx, double E_in, Particle::Bank* site, uint64_t* seed)
{
// Sample cosine of angle -- fission neutrons are always emitted
// isotropically. Sometimes in ACE data, fission reactions actually have
// an angular distribution listed, but for those that do, it's simply just
// a uniform distribution in mu
double mu = 2.0 * prn(seed) - 1.0;
// Sample azimuthal angle uniformly in [0,2*pi)
double phi = 2.0*PI*prn(seed);
site->u.x = mu;
site->u.y = std::sqrt(1.0 - mu*mu) * std::cos(phi);
site->u.z = std::sqrt(1.0 - mu*mu) * std::sin(phi);
// Determine total nu, delayed nu, and delayed neutron fraction
const auto& nuc {data::nuclides[i_nuclide]};
double nu_t = nuc->nu(E_in, Nuclide::EmissionMode::total);
double nu_d = nuc->nu(E_in, Nuclide::EmissionMode::delayed);
double beta = nu_d / nu_t;
double mu;
if (prn(seed) < beta) {
// ====================================================================
// DELAYED NEUTRON SAMPLED
@ -1096,6 +1085,12 @@ void sample_fission_neutron(int i_nuclide, const Reaction& rx, double E_in, Part
}
}
}
// Sample azimuthal angle uniformly in [0, 2*pi) and assign angle
double phi = 2.0*PI*prn(seed);
site->u.x = mu;
site->u.y = std::sqrt(1.0 - mu*mu) * std::cos(phi);
site->u.z = std::sqrt(1.0 - mu*mu) * std::sin(phi);
}
void inelastic_scatter(const Nuclide& nuc, const Reaction& rx, Particle& p)