distribution/detail/Utils.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/em/distribution/detail/Utils.hh
0007 //---------------------------------------------------------------------------//
0008 #pragma once
0009
0010 #include "corecel/Types.hh"
0011 #include "celeritas/Constants.hh"
0012 #include "celeritas/Quantities.hh"
0013 #include "celeritas/phys/ParticleTrackView.hh"
0014
0015 namespace celeritas
0016 {
0017 namespace detail
0018 {
0019 //---------------------------------------------------------------------------//
0020 /*!
0021  * Calculate the maximum energy transferable to a free electron in ionizaation.
0022  *
0023  * This calculates the maximum kinematically allowed kinetic energy of the
0024  * delta ray produced in muon or hadron ionization,
0025  * \f[
0026    T_{max} = \frac{2 m_e c^2 (\gamma^2 - 1)}{1 + 2\gamma (m_e/M) + (m_e/M)^2},
0027  * \f]
0028  * where \f$ m_e \f$ is the electron mass and \f$ M \f$ is the mass of the
0029  * incident particle.
0030  */
0031 inline CELER_FUNCTION units::MevEnergy
0032 calc_max_secondary_energy(ParticleTrackView const& particle,
0033                           units::MevMass electron_mass)
0034 {
0035     real_type inc_mass = value_as<units::MevMass>(particle.mass());
0036     real_type mass_ratio = value_as<units::MevMass>(electron_mass) / inc_mass;
0037     real_type tau = value_as<units::MevEnergy>(particle.energy()) / inc_mass;
0038     return units::MevEnergy{
0039         2 * value_as<units::MevMass>(electron_mass) * tau * (tau + 2)
0040         / (1 + 2 * (tau + 1) * mass_ratio + ipow<2>(mass_ratio))};
0041 }
0042
0043 //---------------------------------------------------------------------------//
0044 }  // namespace detail
0045 }  // namespace celeritas