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/* Copyright 2021 Modern Electron
*
* This file is part of WarpX.
*
* License: BSD-3-Clause-LBNL
*/
#include "MCCProcess.H"
#include "Utils/TextMsg.H"
#include "WarpX.H"
MCCProcess::MCCProcess (
const std::string& scattering_process,
const std::string& cross_section_file,
const amrex::ParticleReal energy )
{
// read the cross-section data file into memory
readCrossSectionFile(cross_section_file, m_energies, m_sigmas_h);
init(scattering_process, energy);
}
template <typename InputVector>
MCCProcess::MCCProcess (
const std::string& scattering_process,
const InputVector&& energies,
const InputVector&& sigmas,
const amrex::ParticleReal energy )
{
m_energies.insert(m_energies.begin(), std::begin(energies), std::end(energies));
m_sigmas_h.insert(m_sigmas_h.begin(), std::begin(sigmas), std::end(sigmas));
init(scattering_process, energy);
}
void
MCCProcess::init (const std::string& scattering_process, const amrex::ParticleReal energy)
{
using namespace amrex::literals;
m_exe_h.m_sigmas_data = m_sigmas_h.data();
// save energy grid parameters for easy use
m_grid_size = m_energies.size();
m_exe_h.m_energy_lo = m_energies[0];
m_exe_h.m_energy_hi = m_energies[m_grid_size-1];
m_exe_h.m_sigma_lo = m_sigmas_h[0];
m_exe_h.m_sigma_hi = m_sigmas_h[m_grid_size-1];
m_exe_h.m_dE = (m_exe_h.m_energy_hi - m_exe_h.m_energy_lo)/(m_grid_size - 1._prt);
m_exe_h.m_energy_penalty = energy;
m_exe_h.m_type = parseProcessType(scattering_process);
// sanity check cross-section energy grid
sanityCheckEnergyGrid(m_energies, m_exe_h.m_dE);
// check that the cross-section is 0 at the energy cost if the energy
// cost is > 0 - this is to prevent the possibility of negative left
// over energy after a collision event
if (m_exe_h.m_energy_penalty > 0) {
WARPX_ALWAYS_ASSERT_WITH_MESSAGE(
(getCrossSection(m_exe_h.m_energy_penalty) == 0),
"Cross-section > 0 at energy cost for collision."
);
}
#ifdef AMREX_USE_GPU
m_exe_d = m_exe_h;
m_sigmas_d.resize(m_sigmas_h.size());
m_exe_d.m_sigmas_data = m_sigmas_d.data();
amrex::Gpu::copyAsync(amrex::Gpu::hostToDevice, m_sigmas_h.begin(), m_sigmas_h.end(),
m_sigmas_d.begin());
amrex::Gpu::streamSynchronize();
#endif
}
MCCProcessType
MCCProcess::parseProcessType(const std::string& scattering_process)
{
if (scattering_process == "elastic") {
return MCCProcessType::ELASTIC;
} else if (scattering_process == "back") {
return MCCProcessType::BACK;
} else if (scattering_process == "charge_exchange") {
return MCCProcessType::CHARGE_EXCHANGE;
} else if (scattering_process == "ionization") {
return MCCProcessType::IONIZATION;
} else if (scattering_process.find("excitation") != std::string::npos) {
return MCCProcessType::EXCITATION;
} else {
return MCCProcessType::INVALID;
}
}
void
MCCProcess::readCrossSectionFile (
const std::string cross_section_file,
amrex::Vector<amrex::ParticleReal>& energies,
amrex::Gpu::HostVector<amrex::ParticleReal>& sigmas )
{
std::ifstream infile(cross_section_file);
if(!infile.is_open()) WARPX_ABORT_WITH_MESSAGE("Failed to open cross-section data file");
amrex::ParticleReal energy, sigma;
while (infile >> energy >> sigma) {
energies.push_back(energy);
sigmas.push_back(sigma);
}
if (infile.bad()) WARPX_ABORT_WITH_MESSAGE("Failed to read cross-section data from file.");
infile.close();
}
void
MCCProcess::sanityCheckEnergyGrid (
const amrex::Vector<amrex::ParticleReal>& energies,
amrex::ParticleReal dE
)
{
// confirm that the input data for the cross-section was provided with
// equal energy steps, otherwise the linear interpolation will fail
for (unsigned i = 1; i < energies.size(); i++) {
WARPX_ALWAYS_ASSERT_WITH_MESSAGE(
(std::abs(energies[i] - energies[i-1] - dE) < dE / 100.0),
"Energy grid not evenly spaced."
);
}
}
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