celeritas::XsCalculator Class Reference

Find and interpolate scaled cross sections. More...

#include <XsCalculator.hh>

Public Types
Type aliases
using	Energy = RealQuantity< XsGridRecord::EnergyUnits >
using	Values = Collection< real_type, Ownership::const_reference, MemSpace::native >

Public Member Functions
CELER_FUNCTION	XsCalculator (XsGridRecord const &grid, Values const &reals)
	Construct from cross section data.
CELER_FUNCTION real_type	operator() (Energy energy) const
	Calculate the cross section using linear or spline interpolation.
CELER_FUNCTION Energy	energy_min () const
	Get the minimum energy.
CELER_FUNCTION Energy	energy_max () const
	Get the maximum energy.

Detailed Description

Find and interpolate scaled cross sections.

This cross section calculator uses the same representation and interpolation as Geant4's physics tables for EM physics:

• The energy grid is uniformly spaced in \(\log E\),
• Values greater than or equal to an index \(i'\) are scaled by E and are stored on a separate energy grid also uniformly spaced in \(\log E\) but not necessarily with the same spacing,
• Linear interpolation between energy points is used to calculate the final value, and
• If the energy is at or above the \(i'\) index, the final result is scaled by \(1/E\).

This scaling and interpolation exactly reproduces functions \( f(E) \sim a E + b \) below the \(E'\) threshold and \( f(E) \sim \frac{a'}{E} + b' \) above that threshold.

Note that linear interpolation is applied with energy points, not log-energy points.

XsCalculator calc_xs(grid, params.reals);
real_type xs = calc_xs(particle.energy());

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

• XsCalculator.hh