Sources

This page describes the public source surfaces that a neomc user can build against today.

Core Source State

Every source eventually produces SourceSite, which wraps a validated ParticleState. A source particle carries:

• position;
• direction;
• energy;
• time;
• weight;
• ParticleType;
• history and generation identifiers;
• optional region and material hints.

SourceSite::to_transport_particle() normalizes direction and converts the source state into a validated TransportParticle.

Independent Sources

IndependentSourceDefinition is the main source type for one transport particle per history.

Spatial Modes

SourceSpatialDefinition supports:

• point
• uniform_box
• uniform_sphere
• uniform_cylinder

The lower-level distribution types exposed in source_distribution.hh are:

• PointSpatialDistribution
• UniformBoxSpatialDistribution
• UniformSphereSpatialDistribution
• UniformCylinderSpatialDistribution

Angular Modes

SourceAngularDefinition supports:

• fixed_direction
• isotropic

The lower-level distribution types are:

• FixedDirectionDistribution
• IsotropicDirectionDistribution

Energy Modes

SourceEnergyDefinition supports:

• monoenergetic
• discrete

The lower-level distribution types are:

• MonoenergeticDistribution
• DiscreteEnergyDistribution

Sampling

Use:

• validate_independent_source_definition
• sample_independent_source
• apply_independent_source_override

The templated IndependentSource<...> wrapper is also public when a caller prefers to compose distributions directly instead of going through IndependentSourceDefinition.

General Multi-Component Sources

GeneralSourceDefinition extends the source surface to multiple weighted source components.

Each GeneralSourceComponentDefinition contains:

• one IndependentSourceDefinition;
• one positive component strength.

Public helpers include:

• validate_general_source_definition
• sample_general_source
• apply_general_source_override
• make_particle_gun_source

This is the source surface used by the application layer when a run needs one or more configurable source components instead of a single hard-coded source.

Static Decay Inventory Sources

StaticDecayInventorySource is the public source type for decay-driven source batches.

Each DecayInventoryItem contains:

• nuclide
• either activity_bq or atoms
• spatial
• optional region_hint
• optional material_hint

The source-level controls are:

• time
• optional source_time_window
• weight
• master_seed
• unsupported_emission_policy

Represented Emission Rates

The current static decay source summary can represent emission rates for:

• photons
• electrons
• positrons
• protons
• neutrons
• alphas

Transport execution routes those emissions only when the corresponding package is enabled for the session. If DecayUnsupportedEmissionPolicy::ignore_unsupported is selected, the source summary still records ignored unsupported emission rates.

Summaries

Use summarize_static_decay_inventory_source to obtain StaticDecayInventorySourceSummary, which reports:

• total activity;
• per-item activity;
• source weight;
• photon emission rate;
• electron emission rate;
• positron emission rate;
• proton emission rate;
• neutron emission rate;
• alpha emission rate;
• transport decay-event rate;
• total transport emission rate;
• expected transport events per decay;
• expected transport emissions per decay;
• weighted transport event rate;
• weighted transport emission rate;
• ignored unsupported emission rate.

Sampling

Use:

• validate_static_decay_inventory_source
• sample_static_decay_inventory_event
• sample_static_decay_inventory_source_sites
• make_static_decay_inventory_source_hook
• make_static_decay_inventory_source_batch

Because a single decay may emit multiple transport particles, the batch hook is the natural source surface for mixed-package transport.

Use mixed_transport_source_from_static_decay when a StaticDecayInventorySourceHook should be converted into a mixed-transport source with source-rate metadata.

Decay Window Sources

DecayInventoryWindowSourceDefinition lets a caller define a source over a time window instead of only at one instant.

Use:

• validate_decay_inventory_window_source_definition
• make_decay_inventory_window_source

The returned DecayInventoryWindowSource contains:

• the evolved static source;
• the inventory evolution result over the window;
• the source summary after normalization.

Decay Inventory Evolution

decay_inventory_evolution.hh exposes related inventory-evolution capabilities:

• evolve_decay_inventory
• evolve_decay_inventory_at_times
• evolve_decay_inventory_over_windows

This is useful when a user needs to derive a static source inventory from a time-evolved nuclide inventory before sampling transport emissions.

Activation Inventory Evolution

activation_inventory_evolution.hh adds a separate source-term capability for one-group activation inventory evolution.

The public types are:

• OneGroupActivationReaction
• OneGroupActivationIrradiation
• OneGroupActivationInventory
• OneGroupActivationResult

Use:

• evolve_one_group_activation_inventory

This is a source-term data path, not neutron transport.

Source Constraints

The public validation rules visible in the headers are:

• transport source particles must have finite position and direction;
• direction must be non-zero;
• energy and weight must be finite and positive;
• time must be finite;
• ParticleType::energy_deposit is not a valid transport source particle;
• decay inventory items may not define both atoms and activity_bq;
• a decay inventory item must define one or the other with a positive value.