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Clean up fusion.param and improve documentation
- Remove all verbose comments and examples from fusion.param - Move complete D-T fusion example to documentation
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‎docs/source/usage/workflows/fusionReactions.rst‎

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@@ -83,6 +83,56 @@ Configure fusion reactions in ``include/picongpu/param/fusion.param``.
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using products = pmacc::mp_list<Pair<PIC_He4, PIC_He4>>;
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Complete Example: D-T Fusion Reaction
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Here is a complete example for the Deuterium-Tritium fusion reaction (D + T → n + He⁴).
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This is the easiest fusion reaction to achieve and is commonly used in fusion energy research.
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The cross-section parameters are based on the Bosch-Hale parameterization from experimental data
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(Source: https://hdl.handle.net/11858/00-001M-0000-0027-6535-1, page 29).
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.. code-block:: cpp
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struct DT
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{
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//! Reactant species: Deuterium and Tritium
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using reactants = pmacc::mp_list<Pair<PIC_Tritons, PIC_Deuterons>>;
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//! Filter for reactants (mandatory for ColliderFromStruct)
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//! Use filter::All to include all particles, or define custom filters
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using FilterPair = OneFilter<filter::All>;
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//! Product species: Neutron and Helium-4
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using products = pmacc::mp_list<Pair<PIC_Neutrons, PIC_He4>>;
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/** Cross-section parameters for D-T fusion */
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struct Params
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{
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//! Gamow constant: BG = π·α·Z₁·Z₂·√(2·μ·c²) in keV^(1/2)
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//! where α is the fine structure constant, Z₁,Z₂ are charges, μ is reduced mass
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static constexpr float_X BG = 34.3827_X;
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//! Bosch-Hale parameterization coefficients for D-T cross-section
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//! These coefficients fit experimental cross-section data
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static constexpr float_X A1 = 6.927e4_X;
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static constexpr float_X A2 = 7.454e8_X;
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static constexpr float_X A3 = 2.050e6_X;
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static constexpr float_X A4 = 5.2002e4_X;
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static constexpr float_X A5 = 0.0_X;
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//! Additional Bosch-Hale coefficients
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static constexpr float_X B1 = 6.38e1_X;
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static constexpr float_X B2 = -9.95e-1_X;
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static constexpr float_X B3 = 6.981e-5_X;
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static constexpr float_X B4 = 1.728e-4_X;
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};
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//! Cross-section calculation using Bosch-Hale parameterization
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//! Returns cross-section in milli-barns
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using CrossSectionInterpolator = relativistic::FusionFunctor<Params>;
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};
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2) Configure the fusion pipeline
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.. code-block:: cpp

‎include/picongpu/param/fusion.param‎

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@@ -31,161 +31,23 @@ namespace picongpu
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{
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namespace fusion
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{
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//! ===================================================================
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//! PRECISION SETTINGS
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//! ===================================================================
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namespace precision
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{
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//! Use double precision for fusion collision calculations
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using float_COLL = float_64;
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} // namespace precision
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using namespace picongpu::plugins;
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//! ===================================================================
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//! FUSION REACTION DEFINITIONS
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//! ===================================================================
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/** Deuterium-Tritium Fusion Reaction
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*
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* This defines the D + T -> n + He4 fusion reaction
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*
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* USAGE: Uncomment this struct to enable D-T fusion in your simulation
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*
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* The cross-section parameters are based on the Bosch-Hale
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* parameterization from experimental data.
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* Source: https://hdl.handle.net/11858/00-001M-0000-0027-6535-1 (page 29)
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/** Define your fusion reactions here.
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* See documentation: https://picongpu.readthedocs.io/en/latest/usage/workflows/fusionReactions.html
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*/
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// struct DT
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// {
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// //! Reactant species: Deuterium and Tritium
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// using reactants = pmacc::mp_list<Pair<PIC_Tritons, PIC_Deuterons>>;
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//
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// //! Product species: Neutron and Helium-4
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// using products = pmacc::mp_list<Pair<PIC_Neutrons, PIC_He4>>;
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//
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// /** Cross-section parameters for D-T fusion */
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// struct Params
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// {
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// //! Gamov constant: BG = pi*alpha*Z1*Z2*sqrt(2*mu*c^2) in keV^(1/2)
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// //! where alpha is fine structure constant, Z1,Z2 are charges, mu is reduced mass
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// static constexpr float_X BG = 34.3827_X;
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//
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// //! Bosch-Hale parameterization coefficients for D-T cross-section
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// //! These coefficients fit experimental cross-section data
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// static constexpr float_X A1 = 6.927e4_X;
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// static constexpr float_X A2 = 7.454e8_X;
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// static constexpr float_X A3 = 2.050e6_X;
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// static constexpr float_X A4 = 5.2002e4_X;
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// static constexpr float_X A5 = 0.0_X;
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//
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// //! Additional Bosch-Hale coefficients
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// static constexpr float_X B1 = 6.38e1_X;
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// static constexpr float_X B2 = -9.95e-1_X;
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// static constexpr float_X B3 = 6.981e-5_X;
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// static constexpr float_X B4 = 1.728e-4_X;
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// };
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// //! For now it's the only cross-section interpolator available
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// //! Cross-section calculation using Bosch-Hale parameterization.
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// //! Returns cross-section in milli-barns.
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// using CrossSectionInterpolator = relativistic::FusionFunctor<Params>;
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// };
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// empty pipeline - no fusion
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using FusionPipeline = pmacc::mp_list<>;
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//! ===================================================================
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//! FUSION PIPELINE CONFIGURATION
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//! ===================================================================
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/** FusionPipeline: Defines the sequence of fusion reactions
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*
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* This controls which fusion reactions occur and in what order.
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* Each reaction is processed sequentially from first to last.
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*
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* USAGE EXAMPLES:
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*
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* 1. Single D-T reaction:
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* using FusionPipeline = pmacc::mp_list<ColliderFromStruct<DT>>;
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*
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* 2. Multiple reactions (processed in order):
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* using FusionPipeline = pmacc::mp_list<
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* ColliderFromStruct<DT>,
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* ColliderFromStruct<DD>,
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* ColliderFromStruct<DHe3>
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* >;
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*
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* 3. Manual collider specification:
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* using FusionPipeline = pmacc::mp_list<
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* Collider<DT::CrossSectionInterpolator,
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* DT::reactants,
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* DT::products,
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* OneFilter<filter::All>>
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* >;
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*/
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//! Method 1: Using ColliderFromStruct (recommended - cleaner syntax)
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// using FusionPipeline = pmacc::mp_list<ColliderFromStruct<DT>>;
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//! Method 2: Manual collider specification
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// using FusionPipeline = pmacc::mp_list<
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// Collider<DT::CrossSectionInterpolator, DT::reactants, DT::products, OneFilter<filter::All>>
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// >;
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// empty pipeline - no fusion
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using FusionPipeline = pmacc::mp_list<>;
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//! ===================================================================
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//! SIMULATION PARAMETERS
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//! ===================================================================
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/** Memory Management Parameters */
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/** Cell list chunk size for memory allocation
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*
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* Controls memory allocation strategy for collision algorithm.
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* The algorithm allocates multiples of this value to store
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* particle ID lists, reducing memory fragmentation on GPUs.
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*
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* Larger values = less fragmentation but more memory overhead
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*/
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constexpr uint32_t cellListChunkSize = TYPICAL_PARTICLES_PER_CELL;
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/** Product Weighting Parameters */
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/** Minimum weighting threshold for fusion products
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*
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* When fusion product weighting <= productMinWeighting, the
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* multiplication factor is set to:
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* Fmult = max(1, productWeighting/productMinWeighting)
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*
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* Fmult is then used to scale the fusion probability:
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* larger Fmult means we produce more products with smaller weighting.
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*
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* note: This does not ensure that the product weighting is always above this threshold - see docs "Fusion
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* Particle Creation Algorithm"
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*/
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constexpr float_X productMinWeighting = 16.1;
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/** Maximum multiplication factor for products
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* the algorithm tries to use this multiplier and if the product weighting is smaller than
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* productMinWeighting, Fusion multiplier will be reduced.
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*
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* Usually set to a value ~10~100x less than the typical particle weighting in a cell.
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*/
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constexpr uint32_t maxFmult = 1e6;
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/** Debug and Control Flags */
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/** Enable detailed fusion debugging output
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* When true: Prints detailed information about fusion events - warning: large output!
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*/
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constexpr bool debugFusion = false;
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/** Force fusion probability to 100%
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* All collision attempts result in fusion
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*/
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constexpr bool alwaysFuseQ = false;
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} // namespace fusion
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} // namespace particles

‎include/picongpu/particles/fusion/relativistic/FusionFunctor.def‎

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/** Host side binary collision functor for using a constant coulomb logarithm value
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*
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* @tparam T_Param param class with a static constexpr member coulombLog
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* @tparam ifDebug if true the simulation output will include a file (or files, one for each collided
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* pair of species) with an average coulomb log and s parameter (averaged over all collisions
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* in the whole simulation, for each timestep)
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* @tparam T_Param param class with a static constexpr member 'CalcCrossSection'
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*/
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template<typename T_Param>
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using FusionFunctor = FusionFunctorImpl<T_Param>;

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