celeritas::EnergyLossUrbanDistribution Class Reference

Sample from the Urban model of energy loss fluctuations in thin layers. More...

#include <EnergyLossUrbanDistribution.hh>

Public Types
Type aliases
using	FluctuationRef = NativeCRef< FluctuationData >
using	Energy = units::MevEnergy
using	Mass = units::MevMass

Public Member Functions
CELER_FUNCTION	EnergyLossUrbanDistribution (FluctuationRef const &shared, MaterialTrackView const &cur_mat, Energy unscaled_mean_loss, Energy max_energy, Mass two_mebsgs, real_type beta_sq)
	Construct from distribution parameters.
CELER_FUNCTION	EnergyLossUrbanDistribution (EnergyLossHelper const &helper)
	Construct from helper-calculated data.
template<class Generator >
CELER_FUNCTION Energy	operator() (Generator &rng)
template<class Generator >
CELER_FUNCTION auto	operator() (Generator &rng) -> Energy
	Sample energy loss according to the distribution.

Detailed Description

Sample from the Urban model of energy loss fluctuations in thin layers.

The Urban model is used to compute the energy loss fluctuation when \( \kappa \) is small. It assumes atoms have only two energy levels with binding energies \( E_1 \) and \( E_2 \) and that the particle-atom interaction will either be an excitation with energy loss \( E_1 \) or \( E_2 \) or an ionization with energy loss proportional to \( 1 / E^2 \). The number of collisions for each interaction type has a Poisson distribution with mean proportional to the interaction cross section. The energy loss in a step will be the sum of the energy loss contributions from excitation and ionization.

When the number of ionizations is larger than a given threshold, a fast sampling method can be used instead. The possible energy loss interval is divided into two parts: a lower range in which the number of collisions is large and the energy loss can be sampled from a Gaussian distribution, and an upper range in which the energy loss is sampled for each collision.

See section 7.3.2 of the Geant4 Physics Reference Manual and GEANT3 PHYS332 section 2.4 for details.

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

• EnergyLossUrbanDistribution.hh