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weights of colliding particles are reduced locally for fusion.
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@JustinRayAngus
JustinRayAngus committed Aug 11, 2024
1 parent fe00327 commit a09b164
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Showing 2 changed files with 50 additions and 28 deletions.
68 changes: 44 additions & 24 deletions Source/Particles/Collision/BinaryCollision/NuclearFusion/NuclearFusionFunc.H
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Original file line number Diff line number Diff line change
Expand Up @@ -145,11 +145,13 @@ public:
amrex::ParticleReal * const AMREX_RESTRICT u1x = soa_1.m_rdata[PIdx::ux];
amrex::ParticleReal * const AMREX_RESTRICT u1y = soa_1.m_rdata[PIdx::uy];
amrex::ParticleReal * const AMREX_RESTRICT u1z = soa_1.m_rdata[PIdx::uz];
uint64_t* AMREX_RESTRICT idcpu1 = soa_1.m_idcpu;

amrex::ParticleReal * const AMREX_RESTRICT w2 = soa_2.m_rdata[PIdx::w];
amrex::ParticleReal * const AMREX_RESTRICT u2x = soa_2.m_rdata[PIdx::ux];
amrex::ParticleReal * const AMREX_RESTRICT u2y = soa_2.m_rdata[PIdx::uy];
amrex::ParticleReal * const AMREX_RESTRICT u2z = soa_2.m_rdata[PIdx::uz];
uint64_t* AMREX_RESTRICT idcpu2 = soa_2.m_idcpu;

// Number of macroparticles of each species
const index_type NI1 = I1e - I1s;
Expand All @@ -174,37 +176,55 @@ public:
for (index_type k = coll_idx; k < max_N; k += min_N)
{

// do not check for collision if a particle's weight was
// reduced to zero from a previous collision
if (idcpu1[ I1[i1] ]==amrex::ParticleIdCpus::Invalid ||
idcpu2[ I2[i2] ]==amrex::ParticleIdCpus::Invalid ) {
p_mask[pair_index] = false;
}
else {

#if (defined WARPX_DIM_RZ)
/* In RZ geometry, macroparticles can collide with other macroparticles
* in the same *cylindrical* cell. For this reason, collisions between macroparticles
* are actually not local in space. In this case, the underlying assumption is that
* particles within the same cylindrical cell represent a cylindrically-symmetry
* momentum distribution function. Therefore, here, we temporarily rotate the
* momentum of one of the macroparticles in agreement with this cylindrical symmetry.
* (This is technically only valid if we use only the m=0 azimuthal mode in the simulation;
* there is a corresponding assert statement at initialization.) */
amrex::ParticleReal const theta = theta2[I2[i2]]-theta1[I1[i1]];
amrex::ParticleReal const u1xbuf = u1x[I1[i1]];
u1x[I1[i1]] = u1xbuf*std::cos(theta) - u1y[I1[i1]]*std::sin(theta);
u1y[I1[i1]] = u1xbuf*std::sin(theta) + u1y[I1[i1]]*std::cos(theta);
/* In RZ geometry, macroparticles can collide with other macroparticles
* in the same *cylindrical* cell. For this reason, collisions between macroparticles
* are actually not local in space. In this case, the underlying assumption is that
* particles within the same cylindrical cell represent a cylindrically-symmetry
* momentum distribution function. Therefore, here, we temporarily rotate the
* momentum of one of the macroparticles in agreement with this cylindrical symmetry.
* (This is technically only valid if we use only the m=0 azimuthal mode in the simulation;
* there is a corresponding assert statement at initialization.) */
amrex::ParticleReal const theta = theta2[I2[i2]]-theta1[I1[i1]];
amrex::ParticleReal const u1xbuf = u1x[I1[i1]];
u1x[I1[i1]] = u1xbuf*std::cos(theta) - u1y[I1[i1]]*std::sin(theta);
u1y[I1[i1]] = u1xbuf*std::sin(theta) + u1y[I1[i1]]*std::cos(theta);
#endif

SingleNuclearFusionEvent(
u1x[ I1[i1] ], u1y[ I1[i1] ], u1z[ I1[i1] ],
u2x[ I2[i2] ], u2y[ I2[i2] ], u2z[ I2[i2] ],
m1, m2, w1[ I1[i1] ], w2[ I2[i2] ],
dt, dV, static_cast<int>(pair_index), p_mask, p_pair_reaction_weight,
m_fusion_multiplier, multiplier_ratio,
m_probability_threshold,
m_probability_target_value,
m_fusion_type, engine);
SingleNuclearFusionEvent(
u1x[ I1[i1] ], u1y[ I1[i1] ], u1z[ I1[i1] ],
u2x[ I2[i2] ], u2y[ I2[i2] ], u2z[ I2[i2] ],
m1, m2, w1[ I1[i1] ], w2[ I2[i2] ],
dt, dV, static_cast<int>(pair_index), p_mask, p_pair_reaction_weight,
m_fusion_multiplier, multiplier_ratio,
m_probability_threshold,
m_probability_target_value,
m_fusion_type, engine);

#if (defined WARPX_DIM_RZ)
amrex::ParticleReal const u1xbuf_new = u1x[I1[i1]];
u1x[I1[i1]] = u1xbuf_new*std::cos(-theta) - u1y[I1[i1]]*std::sin(-theta);
u1y[I1[i1]] = u1xbuf_new*std::sin(-theta) + u1y[I1[i1]]*std::cos(-theta);
amrex::ParticleReal const u1xbuf_new = u1x[I1[i1]];
u1x[I1[i1]] = u1xbuf_new*std::cos(-theta) - u1y[I1[i1]]*std::sin(-theta);
u1y[I1[i1]] = u1xbuf_new*std::sin(-theta) + u1y[I1[i1]]*std::cos(-theta);
#endif

// Remove pair reaction weight from the colliding particles' weights
if (p_mask[pair_index]) {
BinaryCollisionUtils::remove_weight_from_colliding_particle(
w1[ I1[i1] ], idcpu1[ I1[i1] ], p_pair_reaction_weight[pair_index]);
BinaryCollisionUtils::remove_weight_from_colliding_particle(
w2[ I2[i2] ], idcpu2[ I2[i2] ], p_pair_reaction_weight[pair_index]);
}

}

p_pair_indices_1[pair_index] = I1[i1];
p_pair_indices_2[pair_index] = I2[i2];
if (max_N == NI1) {
Expand Down
10 changes: 6 additions & 4 deletions Source/Particles/Collision/BinaryCollision/ParticleCreationFunc.H
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Original file line number Diff line number Diff line change
Expand Up @@ -198,10 +198,12 @@ public:
}

// Remove p_pair_reaction_weight[i] from the colliding particles' weights
BinaryCollisionUtils::remove_weight_from_colliding_particle(
w1[p_pair_indices_1[i]], idcpu1[p_pair_indices_1[i]], p_pair_reaction_weight[i]);
BinaryCollisionUtils::remove_weight_from_colliding_particle(
w2[p_pair_indices_2[i]], idcpu2[p_pair_indices_2[i]], p_pair_reaction_weight[i]);
if (t_collision_type == CollisionType::DSMC) { // performed locally for fusion
BinaryCollisionUtils::remove_weight_from_colliding_particle(
w1[p_pair_indices_1[i]], idcpu1[p_pair_indices_1[i]], p_pair_reaction_weight[i]);
BinaryCollisionUtils::remove_weight_from_colliding_particle(
w2[p_pair_indices_2[i]], idcpu2[p_pair_indices_2[i]], p_pair_reaction_weight[i]);
}

// Initialize the product particles' momentum, using a function depending on the
// specific collision type
Expand Down

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