ShortRF.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: Chad Mitchell, Axel Huebl
 * License: BSD-3-Clause-LBNL
 */
#ifndef IMPACTX_SHORTRF_H
#define IMPACTX_SHORTRF_H
 
#include "particles/ImpactXParticleContainer.H"
#include "mixin/alignment.H"
#include "mixin/beamoptic.H"
#include "mixin/thin.H"
#include "mixin/named.H"
#include "mixin/nofinalize.H"
#include "mixin/lineartransport.H"
 
#include <AMReX_Extension.H>
#include <AMReX_Math.H>
#include <AMReX_REAL.H>
#include <AMReX_SIMD.H>
 
#include <cmath>
 
namespace impactx::elements
{
    struct ShortRF
    : public mixin::Named,
      public mixin::BeamOptic<ShortRF>,
      public mixin::LinearTransport<ShortRF>,
      public mixin::Thin,
      public mixin::Alignment,
      public mixin::NoFinalize,
      public amrex::simd::Vectorized<amrex::simd::native_simd_size_particlereal>
    {
        static constexpr auto type = "ShortRF";
        using PType = ImpactXParticleContainer::ParticleType;
 
        static constexpr amrex::ParticleReal DEFAULT_phase = -90;

        ShortRF (
            amrex::ParticleReal V,
            amrex::ParticleReal freq,
            amrex::ParticleReal phase = DEFAULT_phase,
            amrex::ParticleReal dx = DEFAULT_dx,
            amrex::ParticleReal dy = DEFAULT_dy,
            amrex::ParticleReal rotation_degree = DEFAULT_rotation_degree,
            std::optional<std::string> name = DEFAULT_name
        )
        : Named(std::move(name)),
          Alignment(dx, dy, rotation_degree),
          m_V(V), m_freq(freq), m_phase(phase)
        {
        }

        void reverse () { m_V = -m_V; }

        using BeamOptic::operator();

        void compute_constants (RefPart const & refpart)
        {
            using namespace amrex::literals; // for _rt and _prt
            using amrex::Math::powi;
 
            Alignment::compute_constants(refpart);
 
            // Define parameters and intermediate constants
            using ablastr::constant::math::pi;
            using ablastr::constant::SI::c;
            m_k = 2.0_prt * pi / c * m_freq;
            m_phi = m_phase * pi / 180.0_prt;
 
            // access reference particle values (final, initial):
            amrex::ParticleReal const ptf_ref = refpart.pt;
            m_V_cos_phi = m_V * std::cos(m_phi);
            amrex::ParticleReal const pti_ref = ptf_ref + m_V_cos_phi;
            m_bgf = std::sqrt(powi<2>(ptf_ref) - 1.0_prt);
            m_bgi = std::sqrt(powi<2>(pti_ref) - 1.0_prt);
        }

        template<typename T_Real=amrex::ParticleReal, typename T_IdCpu=uint64_t>
        AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
        void operator() (
            [[maybe_unused]] T_Real const & AMREX_RESTRICT x,
            [[maybe_unused]] T_Real const & AMREX_RESTRICT y,
            T_Real const & AMREX_RESTRICT t,
            T_Real & AMREX_RESTRICT px,
            T_Real & AMREX_RESTRICT py,
            T_Real & AMREX_RESTRICT pt,
            [[maybe_unused]] T_IdCpu const & AMREX_RESTRICT idcpu,
            [[maybe_unused]] RefPart const & AMREX_RESTRICT refpart
        ) const
        {
 
            using namespace amrex::literals; // for _rt and _prt
            using namespace std; // for cmath(float)
 
            // initial conversion from static to dynamic units:
            px = px * m_bgi;
            py = py * m_bgi;
            pt = pt * m_bgi;
 
            // initialize output values
            // T_Real xout = x;
            // T_Real yout = y;
            // T_Real tout = t;
            // T_Real pxout = px;
            // T_Real pyout = py;
            T_Real ptout = pt;
 
            // advance position and momentum in dynamic units
            // xout = x;
            // pxout = px;
 
            // yout = y;
            // pyout = py;
 
            // tout = t;
            ptout = pt - m_V * cos(m_k * t + m_phi) + m_V_cos_phi;
 
            // assign updated values
            // x = xout;
            // y = yout;
            // t = tout;
            // px = pxout;
            // py = pyout;
            pt = ptout;
 
            // final conversion from dynamic to static units:
            px = px / m_bgf;
            py = py / m_bgf;
            pt = pt / m_bgf;
        }

        using Thin::operator();

        AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
        void operator() (RefPart & AMREX_RESTRICT refpart) const
        {
            using namespace amrex::literals; // for _rt and _prt
            using amrex::Math::powi;
 
            // assign input reference particle values
            amrex::ParticleReal const x = refpart.x;
            amrex::ParticleReal const px = refpart.px;
            amrex::ParticleReal const y = refpart.y;
            amrex::ParticleReal const py = refpart.py;
            amrex::ParticleReal const z = refpart.z;
            amrex::ParticleReal const pz = refpart.pz;
            amrex::ParticleReal const t = refpart.t;
            amrex::ParticleReal const pt = refpart.pt;
 
            // Define parameters and intermediate constants
            using ablastr::constant::math::pi;
            amrex::ParticleReal const phi = m_phase*(pi/180.0_prt);
 
            // compute initial value of beta*gamma
            amrex::ParticleReal const bgi = std::sqrt(powi<2>(pt) - 1.0_prt);
 
            // advance pt
            refpart.pt = pt - m_V * std::cos(phi);
 
            // compute final value of beta*gamma
            amrex::ParticleReal const ptf = refpart.pt;
            amrex::ParticleReal const bgf = std::sqrt(powi<2>(ptf) - 1.0_prt);
 
            // advance position (x,y,z,t)
            refpart.x = x;
            refpart.y = y;
            refpart.z = z;
            refpart.t = t;
 
            // advance momentum (px,py,pz)
            refpart.px = px*bgf/bgi;
            refpart.py = py*bgf/bgi;
            refpart.pz = pz*bgf/bgi;
 
        }

        using LinearTransport::operator();

        AMREX_GPU_HOST AMREX_FORCE_INLINE
        Map6x6
        transport_map ([[maybe_unused]] RefPart const & AMREX_RESTRICT refpart) const
        {
            using namespace amrex::literals; // for _rt and _prt
            using amrex::Math::powi;
 
            // Define parameters and intermediate constants
            using ablastr::constant::math::pi;
            using ablastr::constant::SI::c;
            amrex::ParticleReal const k = (2.0_prt*pi/c)*m_freq;
            amrex::ParticleReal const phi = m_phase*(pi/180.0_prt);
 
            // access reference particle values (final, initial):
            amrex::ParticleReal const ptf_ref = refpart.pt;
            amrex::ParticleReal const pti_ref = ptf_ref + m_V * std::cos(phi);
            amrex::ParticleReal const bgf = std::sqrt(powi<2>(ptf_ref) - 1.0_prt);
            amrex::ParticleReal const bgi = std::sqrt(powi<2>(pti_ref) - 1.0_prt);
 
            // initialize transport matrix
            Map6x6 R = Map6x6::Identity();
 
            // This is a nonlinear element: the linearized map is returned here.
            // assign linear map matrix elements
            R(2,2) = bgi/bgf;
            R(4,4) = bgi/bgf;
            R(6,5) = k*m_V*std::sin(phi)/bgf;
            R(6,6) = bgi/bgf;
 
            // apply the transverse rotation (roll) alignment error
            return rotate_aligned_map(R);
        }
 
        amrex::ParticleReal m_V; 
        amrex::ParticleReal m_freq; 
        amrex::ParticleReal m_phase; 
 
      private:
        // constants that are independent of the individually tracked particle,
        // see: compute_constants() to refresh
        amrex::ParticleReal m_k, m_phi, m_V_cos_phi, m_bgi, m_bgf;
    };
 
} // namespace impactx
 
IMPACTX_PUSH_EXTERN_TEMPLATE(impactx::elements::ShortRF)
 
#endif // IMPACTX_SHORTRF_H