HardEdgedQuadrupole.H

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/* Copyright 2022 David Grote
 *
 * This file is part of WarpX.
 *
 * License: BSD-3-Clause-LBNL
 */
#ifndef WARPX_ACCELERATORLATTICE_LATTICEELEMENTS_HARDEDGEDQUADRUPOLE_H_
#define WARPX_ACCELERATORLATTICE_LATTICEELEMENTS_HARDEDGEDQUADRUPOLE_H_
 
#include "LatticeElementBase.H"
#include "HardEdged_K.H"
 
#include <AMReX_REAL.H>
#include <AMReX_ParmParse.H>
#include <AMReX_GpuContainers.H>
 
#include <string>
 
// Specifies a field that models the field generated by a quadrupole lens,
// an axially uniform quadrupole field
 
struct HardEdgedQuadrupoleDevice;
 
struct HardEdgedQuadrupole
    : LatticeElementBase
{
 
    HardEdgedQuadrupole ();

    void
    AddElement (amrex::ParmParse & pp_element, amrex::ParticleReal & z_location);

    void
    WriteToDevice ();
 
    /* The field gradients */
    /* On the host */
    std::vector<amrex::ParticleReal> h_dEdx;
    std::vector<amrex::ParticleReal> h_dBdx;
    /* On the device */
    amrex::Gpu::DeviceVector<amrex::ParticleReal> d_dEdx;
    amrex::Gpu::DeviceVector<amrex::ParticleReal> d_dBdx;

    [[nodiscard]] HardEdgedQuadrupoleDevice
    GetDeviceInstance () const;
 
};
 
// Instance that is trivially copyable to the device.
 
struct HardEdgedQuadrupoleDevice
{

    void InitHardEdgedQuadrupoleDevice (HardEdgedQuadrupole const& h_quad);
 
    int nelements = 0;
 
    const amrex::ParticleReal* AMREX_RESTRICT d_zs_arr;
    const amrex::ParticleReal* AMREX_RESTRICT d_ze_arr;
 
    const amrex::ParticleReal* AMREX_RESTRICT d_dEdx_arr;
    const amrex::ParticleReal* AMREX_RESTRICT d_dBdx_arr;

    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
    void get_field (const int ielement,
                    const amrex::ParticleReal x,
                    const amrex::ParticleReal y,
                    const amrex::ParticleReal z,
                    const amrex::ParticleReal zpvdt,
                    amrex::ParticleReal& Ex,
                    amrex::ParticleReal& Ey,
                    amrex::ParticleReal& Bx,
                    amrex::ParticleReal& By) const
    {
 
        // Calculate the residence correction, the fraction of the time step that the particle
        // spends inside the hard edged element.
        amrex::ParticleReal const frac = hard_edged_fraction(z, zpvdt, d_zs_arr[ielement], d_ze_arr[ielement]);
 
        const amrex::ParticleReal dEdx = frac*d_dEdx_arr[ielement];
        const amrex::ParticleReal dBdx = frac*d_dBdx_arr[ielement];
 
        Ex = +x*dEdx;
        Ey = -y*dEdx;
        Bx = +y*dBdx;
        By = +x*dBdx;
 
    }
 
};
 
#endif // WARPX_ACCELERATORLATTICE_LATTICEELEMENTS_HARDEDGEDQUADRUPOLE_H_