WakeConvolution.H

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/* Copyright 2022-2026 The Regents of the University of California, through Lawrence
 *           Berkeley National Laboratory (subject to receipt of any required
 *           approvals from the U.S. Dept. of Energy). All rights reserved.
 *
 * This file is part of ImpactX.
 *
 * Authors: Alex Bojanich, Chad Mitchell, Axel Huebl
 * License: BSD-3-Clause-LBNL
 */
#ifndef WAKE_CONVOLUTION_H
#define WAKE_CONVOLUTION_H
 
#include "particles/ImpactXParticleContainer.H"
 
#include <AMReX_GpuContainers.H>
#include <AMReX_Math.H>
#include <AMReX_REAL.H>
 
 
namespace impactx::particles::wakefields
{
    // Constants
    constexpr amrex::Real Z0 = 377;  

    constexpr amrex::Real alpha_1 = static_cast<amrex::Real>(0.4648);

    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
    amrex::Real
    unit_step (amrex::Real s)
    {
        using namespace amrex::literals;
 
        return s >= 0_rt ? 1_rt : 0_rt;
    }

    amrex::Real alpha (amrex::Real s);

    amrex::Real w_t_rf (
        amrex::Real s,
        amrex::Real a,
        amrex::Real g,
        amrex::Real L
    );

    amrex::Real w_l_rf (
        amrex::Real s,
        amrex::Real a,
        amrex::Real g,
        amrex::Real L
    );

    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
    amrex::Real
    w_l_csr (
        amrex::Real s,
        amrex::Real R,
        amrex::Real const bin_size
    )
    {
        using namespace amrex::literals;
        using amrex::Math::powi;
 
        amrex::Real const rc = powi<2>(ablastr::constant::SI::q_e) / (4_rt * ablastr::constant::math::pi * ablastr::constant::SI::epsilon_0 * ablastr::constant::SI::m_e * powi<2>(ablastr::constant::SI::c));
        amrex::Real const kappa = (2_rt * rc * ablastr::constant::SI::m_e * powi<2>(ablastr::constant::SI::c)) / std::pow(3_rt, 1_rt/3_rt) / std::pow(R, 2_rt/3_rt);
 
        return -3_rt/2_rt * kappa / bin_size * (unit_step(s + bin_size / 2_rt) * std::pow(std::abs(s + bin_size / 2_rt), 2_rt/3_rt) - unit_step(s - bin_size / 2_rt) * std::pow(std::abs(s - bin_size / 2_rt), 2_rt/3_rt));
    }

    amrex::Gpu::DeviceVector<amrex::Real>
    convolve_fft (
        amrex::Gpu::DeviceVector<amrex::Real> const & beam_profile_slope,
        amrex::Gpu::DeviceVector<amrex::Real> const & wake_func,
        amrex::Real delta_t
    );
 
} // namespace impactx::particles::wakefields
 
#endif // WAKE_CONVOLUTION_H