Physics data for a track. More...

#include <PhysicsTrackView.hh>

Public Types
Type aliases
using	Initializer_t = PhysicsTrackInitializer

using	PhysicsParamsRef = NativeCRef< PhysicsParamsData >

using	PhysicsStateRef = NativeRef< PhysicsStateData >

using	Energy = units::MevEnergy

using	ModelFinder = GridIdFinder< Energy, ParticleModelId >

using	UniformTableId = OpaqueId< UniformTable >

Public Member Functions
	PhysicsTrackView (PhysicsParamsRef const &params, PhysicsStateRef const &states, ParticleTrackView const &particle, PhysMatId material, TrackSlotId tid)
	Construct from shared and state data.

PhysicsTrackView &	operator= (Initializer_t const &)
	Initialize the track view.

void	interaction_mfp (real_type)
	Set the distance to the next interaction, in mean free paths.

void	reset_interaction_mfp ()
	Set the distance to the next interaction, in mean free paths.

void	dedx_range (real_type)
	Set the energy loss range for the current material and particle energy.

void	msc_range (MscRange const &)
	Set the range properties for multiple scattering.

bool	has_interaction_mfp () const
	Whether the remaining MFP has been calculated.

real_type	interaction_mfp () const
	Remaining MFP to interaction.

real_type	dedx_range () const
	Energy loss range.

MscRange const &	msc_range () const
	Persistent range properties for multiple scattering within a same volume.

PhysMatId	material_id () const
	Current material identifier.

ParticleProcessId::size_type	num_particle_processes () const
	Number of processes that apply to this track.

ProcessId	process (ParticleProcessId) const
	Process ID for the given within-particle process index.

XsGridId	macro_xs_grid (ParticleProcessId) const
	Return macro xs value grid data for the given process if available.

UniformGridId	energy_loss_grid () const
	Return the energy loss grid data if available.

UniformGridId	range_grid () const
	Return the range grid data if available.

UniformGridId	inverse_range_grid () const
	Return the inverse range grid data if available.

IntegralXsProcess const &	integral_xs_process (ParticleProcessId ppid) const
	Get data for processes that use the integral approach.

real_type	calc_xs (ParticleProcessId ppid, MaterialView const &material, Energy energy) const
	Calculate macroscopic cross section for the process.

real_type	calc_max_xs (IntegralXsProcess const &process, ParticleProcessId ppid, MaterialView const &material, Energy energy) const
	Estimate maximum macroscopic cross section for the process over the step.

ModelFinder	make_model_finder (ParticleProcessId) const
	Models that apply to the given process ID.

UniformTableId	cdf_table (ParticleModelId) const
	Return value table data for the given particle/model/material.

TabulatedElementSelector	make_element_selector (UniformTableId, Energy) const
	Construct an element selector to sample an element from tabulated xs data.

ParticleProcessId	at_rest_process () const
	ID of the particle's at-rest process.

ModelId	action_to_model (ActionId) const
	Convert an action to a model ID for diagnostics, false if not a model.

ActionId	model_to_action (ModelId) const
	Convert a selected model ID into a simulation action ID.

ModelId	model_id (ParticleModelId) const
	Get the model ID corresponding to the given ParticleModelId.

real_type	range_to_step (real_type range) const
	Calculate scaled step range.

PhysicsParamsScalars const &	scalars () const
	Access scalar properties (options, IDs).

ParticleScalars const &	particle_scalars () const
	Access particle-dependent scalar properties.

size_type	num_particles () const
	Number of particle types.

template<class T >
T	make_calculator (UniformGridId) const
	Construct a grid calculator of the given type.

ModelId	hardwired_model (ParticleProcessId ppid, Energy energy) const
	Get a hardwired model for on-the-fly cross section calculation.

Detailed Description

Physics data for a track.

The physics track view provides an interface for data and operations common to most processes and models.

Constructor & Destructor Documentation

◆ PhysicsTrackView()

celeritas::PhysicsTrackView::PhysicsTrackView	(	PhysicsParamsRef const &	params,
		PhysicsStateRef const &	states,
		ParticleTrackView const &	particle,
		PhysMatId	mid,
		TrackSlotId	tid
	)

inline

Construct from shared and state data.

Particle and material IDs are derived from other class states.

Member Function Documentation

◆ at_rest_process()

ParticleProcessId celeritas::PhysicsTrackView::at_rest_process ( ) const

inline

ID of the particle's at-rest process.

If the particle can have a discrete interaction at rest, this returns the ParticleProcessId of that process. Otherwise, it returns a null ID.

◆ calc_max_xs()

real_type celeritas::PhysicsTrackView::calc_max_xs	(	IntegralXsProcess const &	process,
		ParticleProcessId	ppid,
		MaterialView const &	material,
		Energy	energy
	)		const

inline

Estimate maximum macroscopic cross section for the process over the step.

If this is a particle with an energy loss process, this returns the estimate of the maximum cross section over the step. If the energy of the global maximum of the cross section (calculated at initialization) is in the interval \( [\xi E_0, E_0) \), where \( E_0 \) is the pre-step energy and \( \xi \) is min_eprime_over_e (defined by default as \( \xi = 1 - \alpha \), where \( \alpha \) is max_step_over_range), \( \sigma_{\max} \) is set to the global maximum. Otherwise, \( \sigma_{\max} = \max( \sigma(E_0), \sigma(\xi E_0) ) \). If the cross section is not monotonic in the interval \( [\xi E_0, E_0) \) and the interval does not contain the global maximum, the post-step cross section \( \sigma(E_1) \) may be larger than \( \sigma_{\max} \).

◆ cdf_table()

auto celeritas::PhysicsTrackView::cdf_table ( ParticleModelId pmid ) const

inline

Return value table data for the given particle/model/material.

A null result means either the model is material independent or the material only has one element, so no cross section CDF tables are stored.

◆ dedx_range()

void celeritas::PhysicsTrackView::dedx_range ( real_type range )

inline

Set the energy loss range for the current material and particle energy.

This value will be calculated once at the beginning of each step.

◆ hardwired_model()

ModelId celeritas::PhysicsTrackView::hardwired_model	(	ParticleProcessId	ppid,
		Energy	energy
	)		const

inline

Get a hardwired model for on-the-fly cross section calculation.

This returns the model ID that applies to the given process ID and energy if the process is hardwired to calculate macroscopic cross sections on the fly. If the result is null, tables should be used for this process/energy.

◆ integral_xs_process()

auto celeritas::PhysicsTrackView::integral_xs_process ( ParticleProcessId ppid ) const

inline

Get data for processes that use the integral approach.

Particles that have energy loss processes will have a different energy at the pre- and post-step points. This means the assumption that the cross section is constant along the step is no longer valid. Instead, Monte Carlo integration can be used to sample the interaction length for the discrete process with the correct probability from the exact distribution,

\[ p = 1 - \exp \left( -\int_{E_0}^{E_1} n \sigma(E) \dif s \right), \]

where \( E_0 \) is the pre-step energy, \( E_1 \) is the post-step energy, n is the atom density, and s is the interaction length.

At the start of the step, the maximum value of the cross section over the step \( \sigma_{max} \) is estimated and used as the macroscopic cross section for the process rather than \( \sigma_{E_0} \). After the step, the new value of the cross section \( \sigma(E_1) \) is calculated, and the discrete interaction for the process occurs with probability

\[ p = \frac{\sigma(E_1)}{\sigma_{\max}}. \]

See section 7.4 of the Geant4 Physics Reference (release 10.6) for details.

◆ interaction_mfp()

void celeritas::PhysicsTrackView::interaction_mfp ( real_type mfp )

inline

Set the distance to the next interaction, in mean free paths.

This value will be decremented at each step.

◆ inverse_range_grid()

UniformGridId celeritas::PhysicsTrackView::inverse_range_grid ( ) const

inline

Return the inverse range grid data if available.

If spline interpolation is used, the inverse grid is explicitly stored with the derivatives calculated using the range as the x values and the energy as the y values.

The grid and values are identical to the range grid (i.e., not inverted) even if the inverse grid is explicitly stored: the inversion is done in the InverseRangeCalculator .

◆ make_calculator()

template<class T >

T celeritas::PhysicsTrackView::make_calculator ( UniformGridId id ) const

inline

Construct a grid calculator of the given type.

The calculator must take two arguments: a reference to UniformGridRecord and a reference to the backend reals storage.

◆ msc_range()

void celeritas::PhysicsTrackView::msc_range ( MscRange const & msc_range )

inline

Set the range properties for multiple scattering.

These values will be calculated at the first step in every tracking volume.

◆ particle_scalars()

ParticleScalars const & celeritas::PhysicsTrackView::particle_scalars ( ) const

inline

Access particle-dependent scalar properties.

These properties are different for light particles (electrons/positrons) and heavy particles (muons/hadrons).

◆ range_to_step()

real_type celeritas::PhysicsTrackView::range_to_step ( real_type range ) const

inline

Calculate scaled step range.

This is the updated step function given by Eq. 7.4 of Geant4 Physics Reference Manual, Release 10.6:

\[ s = \alpha r + \rho (1 - \alpha) (2 - \frac{\rho}{r}) \]

where alpha is max_step_over_range and rho is min_range .

Below min_range, no step scaling is applied, but the step can still be arbitrarily small.

◆ reset_interaction_mfp()

void celeritas::PhysicsTrackView::reset_interaction_mfp ( )

inline

Set the distance to the next interaction, in mean free paths.

This value will be decremented at each step.

The documentation for this class was generated from the following file:

phys/PhysicsTrackView.hh

Public Types

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ PhysicsTrackView()

Member Function Documentation

◆ at_rest_process()

◆ calc_max_xs()

◆ cdf_table()

◆ dedx_range()

◆ hardwired_model()

◆ integral_xs_process()

◆ interaction_mfp()

◆ inverse_range_grid()

◆ make_calculator()

◆ msc_range()

◆ particle_scalars()

◆ range_to_step()

◆ reset_interaction_mfp()