celeritas/grid/RangeGridCalculator.hh

0001 //----------------------------------*-C++-*----------------------------------//
0002 // Copyright 2024 UT-Battelle, LLC, and other Celeritas developers.
0003 // See the top-level COPYRIGHT file for details.
0004 // SPDX-License-Identifier: (Apache-2.0 OR MIT)
0005 //---------------------------------------------------------------------------//
0006 //! \file celeritas/grid/RangeGridCalculator.hh
0007 //---------------------------------------------------------------------------//
0008 #pragma once
0009
0010 #include <vector>
0011
0012 #include "corecel/Assert.hh"
0013 #include "corecel/Macros.hh"
0014 #include "corecel/Types.hh"
0015 #include "corecel/data/Collection.hh"
0016 #include "corecel/grid/SplineDerivCalculator.hh"
0017 #include "corecel/grid/UniformGrid.hh"
0018 #include "corecel/grid/UniformGridData.hh"
0019 #include "celeritas/Quantities.hh"
0020 #include "celeritas/inp/Grid.hh"
0021
0022 namespace celeritas
0023 {
0024 //---------------------------------------------------------------------------//
0025 /*!
0026  * Calculate the range from the energy loss.
0027  *
0028  * The range of a particle with energy \f$ E_0 \f$ is calculated by integrating
0029  * the reciprocal of the stopping power over the energy:
0030  * \f[
0031    R(E_0) = \int_0^{E_0} - \difd{x}{E} \dif E.
0032  * \f]
0033  * Given an energy loss grid for a single particle type and material, this
0034  * numerically integrates the range.  To keep the range tables as consistent as
0035  * possible with what we've been importing from Geant4, this performs the same
0036  * calculation as in Geant4's \c G4LossTableBuilder::BuildRangeTable, which
0037  * uses the midpoint rule with 100 substeps for improved accuracy.
0038  *
0039  * The calculator is constructed with the boundary conditions for cubic spline
0040  * interpolation. If the default constructor is used, or if the number of grid
0041  * points is less than 5, linear interpolation will be used instead.
0042  *
0043  * \todo support polynomial interpolation as well?
0044  */
0045 class RangeGridCalculator
0046 {
0047   public:
0048     //!@{
0049     //! \name Type aliases
0050     using BC = SplineDerivCalculator::BoundaryCondition;
0051     //!@}
0052
0053   public:
0054     // Default constructor
0055     RangeGridCalculator();
0056
0057     // Construct with boundary conditions for spline interpolation
0058     explicit RangeGridCalculator(BC);
0059
0060     // Calculate the range from the energy loss for a single material
0061     inp::UniformGrid operator()(inp::UniformGrid const&) const;
0062
0063   private:
0064     BC bc_;
0065
0066     //! Number of substeps in the numerical integration
0067     static constexpr size_type integration_substeps() { return 100; }
0068 };
0069
0070 //---------------------------------------------------------------------------//
0071 }  // namespace celeritas