Settable parameters and default values for Urban multiple scattering. More...

#include <UrbanMscData.hh>

Public Types
using	Energy = units::MevEnergy

Public Attributes
real_type	tau_small {1e-16}
	small value of tau

real_type	tau_big {8}
	big value of tau

real_type	tau_limit {1e-6}
	limit of tau

real_type	safety_tol {0.01}
	safety tolerance

real_type	geom_limit {5e-8 * units::millimeter}
	minimum step

Energy	low_energy_limit {0}

Energy	high_energy_limit {0}

Static Public Attributes
static constexpr real_type	small_range_frac {0.05}
	Assume constant xs if step / range < small_range_frac ("dtrl")

static constexpr real_type	min_step {0.01 * units::nanometer}
	For steps smaller than this, ignore MSC.

static constexpr real_type	min_step_fallback {10.0 * min_step}
	Minimum true path when not calculated in the step limiting.

static constexpr real_type	min_step_transform
	For steps smaller than this, true path = geometrical path.

static constexpr Energy	min_endpoint_energy {1e-6}
	Below this endpoint energy, don't sample scattering: 1 eV.

static constexpr Energy	min_scaling_energy {5e-3}
	The lower bound of energy to scale the minimum true path length limit.

Detailed Description

Settable parameters and default values for Urban multiple scattering.

\( \tau = t/\lambda \) where t is the true path length and \( \lambda \) is the mean free path of the multiple scattering. The range and safety factors are used in step limitation algorithms and default values are chosen to balance between simulation time and precision.

Mapping of parameter names from Geant4 to Celeritas
Geant4 Symbol	Celeritas Symbol
`dtrl`	`small_range_frac`
`tlimitminfix`	`min_step`
`stepmin`	`min_step_fallback`
`tlimitminfix2`	`min_step_transform`
(hardcoded)	`min_endpoint_energy`
`tlow`	`min_scaling_energy`