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#ifndef WARPX_PARTICLES_GATHER_SCALEFIELDS_H_
#define WARPX_PARTICLES_GATHER_SCALEFIELDS_H_
#include "Particles/WarpXParticleContainer.H"
#include <AMReX_REAL.H>
#include <limits>
/** \brief Functor that scales E and B by a factor before pushing the particles.
* This is used for rigid injection.
*/
struct ScaleFields
{
bool m_do_scale;
amrex::Real m_dt;
amrex::Real m_z_plane_previous;
amrex::Real m_vz_ave_boosted;
amrex::Real m_v_boost;
ScaleFields(bool do_scale) noexcept
: m_do_scale(do_scale)
{}
ScaleFields (bool do_scale, amrex::Real dt, amrex::Real z_plane_previous,
amrex::Real vz_ave_boosted, amrex::Real v_boost) noexcept
: m_do_scale(do_scale), m_dt(dt), m_z_plane_previous(z_plane_previous),
m_vz_ave_boosted(vz_ave_boosted), m_v_boost(v_boost)
{}
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
void operator () (amrex::ParticleReal /*xp*/,
amrex::ParticleReal /*yp*/,
amrex::ParticleReal zp,
amrex::ParticleReal& Exp,
amrex::ParticleReal& Eyp,
amrex::ParticleReal& Ezp,
amrex::ParticleReal& Bxp,
amrex::ParticleReal& Byp,
amrex::ParticleReal& Bzp) const noexcept
{
using namespace amrex::literals;
if (!m_do_scale) return;
// Scale the fields of particles about to cross the injection plane.
// This only approximates what should be happening. The particles
// should by advanced a fraction of a time step instead.
// Scaling the fields is much easier and may be good enough.
const amrex::Real dtscale = m_dt - (m_z_plane_previous - zp)/(m_vz_ave_boosted + m_v_boost);
if (0._rt < dtscale && dtscale < m_dt)
{
Exp *= dtscale;
Eyp *= dtscale;
Ezp *= dtscale;
Bxp *= dtscale;
Byp *= dtscale;
Bzp *= dtscale;
}
}
};
#endif
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