DipEdge.H

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/* Copyright 2022-2023 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_DIPEDGE_H
#define IMPACTX_DIPEDGE_H
 
#include "particles/ImpactXParticleContainer.H"
#include "mixin/alignment.H"
#include "mixin/beamoptic.H"
#include "mixin/thin.H"
#include "mixin/lineartransport.H"
#include "mixin/named.H"
#include "mixin/nofinalize.H"
 
#include <AMReX_Enum.H>
#include <AMReX_Extension.H>
#include <AMReX_Math.H>
#include <AMReX_REAL.H>
#include <AMReX_SIMD.H>
 
#include <cmath>
#include <stdexcept>
 
 
namespace impactx::elements
{
    namespace dipedge
    {
        AMREX_ENUM(Model,
            linear,   
            nonlinear 
        );
        AMREX_ENUM(Location,
            entry, 
            exit  
        );
    }
 
    struct DipEdge
    : public mixin::Named,
      public mixin::BeamOptic<DipEdge>,
      public mixin::LinearTransport<DipEdge>,
      public mixin::Thin,
      public mixin::Alignment,
      public mixin::NoFinalize
      // At least on Intel AVX512, there is a small overhead to vectorize this element, see
      // https://github.com/BLAST-ImpactX/impactx/pull/1002
      // verify again after https://github.com/BLAST-ImpactX/impactx/pull/1158
      // public amrex::simd::Vectorized<amrex::simd::native_simd_size_particlereal>
    {
        static constexpr auto type = "DipEdge";
        using PType = ImpactXParticleContainer::ParticleType;

        DipEdge (
            amrex::ParticleReal psi,
            amrex::ParticleReal rc,
            amrex::ParticleReal g,
            amrex::ParticleReal R,
            amrex::ParticleReal K0,
            amrex::ParticleReal K1,
            amrex::ParticleReal K2,
            amrex::ParticleReal K3,
            amrex::ParticleReal K4,
            amrex::ParticleReal K5,
            amrex::ParticleReal K6,
            dipedge::Model model,
            dipedge::Location location,
            bool modify_ref_part = false,
            amrex::ParticleReal dx = 0,
            amrex::ParticleReal dy = 0,
            amrex::ParticleReal rotation_degree = 0,
            std::optional<std::string> name = std::nullopt
        )
        : Named(std::move(name)),
          Alignment(dx, dy, rotation_degree),
          m_psi(psi), m_rc(rc), m_g(g), m_R(R), m_K0(K0), m_K1(K1), m_K2(K2), m_K3(K3), m_K4(K4), m_K5(K5), m_K6(K6), m_model(model), m_location(location), m_modify_ref_part(modify_ref_part)
        {
        }

        void reverse ()
        {
            m_psi = -m_psi;
            m_K2 = -m_K2;
            m_location = (m_location == dipedge::Location::entry)
                ? dipedge::Location::exit
                : dipedge::Location::entry;
        }

        using BeamOptic::operator();

        void compute_constants ([[maybe_unused]] RefPart const & refpart)
        {
            using namespace amrex::literals; // for _rt and _prt
            using amrex::Math::powi;
 
            Alignment::compute_constants(refpart);
 
            // constants for linear map:
 
            // edge focusing matrix elements (zero gap)
            m_R21 = std::tan(m_psi) / m_rc;
 
            // first-order effect of nonzero gap
            auto const [sin_psi, cos_psi] = amrex::Math::sincos(m_psi);
            amrex::ParticleReal const vf = (1.0_prt + powi<2>(sin_psi))
                / powi<3>(cos_psi)
                * m_g * m_K2 / powi<2>(m_rc);
 
            m_R43 = vf - m_R21;
 
            // constants for nonlinear map:
 
            // access reference particle values to find beta
            m_beta = refpart.beta();
 
            // expressions from eq (14) of Mitchell and Hwang, NAPAC2025
            amrex::ParticleReal const tan_psi = sin_psi/cos_psi;
            amrex::ParticleReal const sec_psi = 1_prt/cos_psi;
 
            // the scale constant specifying entry or exit
            amrex::ParticleReal const loc = m_location == dipedge::Location::entry ? 1_prt : -1_prt;
 
            m_c1 = (m_g / m_rc) * m_K1 / cos_psi;
            m_c2_times_1plusdelta = powi<2>(m_g/m_rc) * m_K0 * sin_psi * powi<3>(sec_psi)/2_prt;
            m_c3_times_1plusdelta = loc * powi<2>(m_g)/m_rc * m_K0 * powi<2>(sec_psi);
            m_c4_times_1plusdelta = loc * (m_g / m_rc) * m_K1 * sin_psi / (powi<2>(cos_psi));
            m_c5 = tan_psi / (2_prt * m_rc);
            m_c6_times_1plusdelta = 0.5_prt * powi<2>(sin_psi)/(2_prt * m_rc * powi<3>(cos_psi)) * m_g/m_rc * m_K1;
            m_c7_times_1plusdelta = 0.5_prt * powi<3>(sec_psi) * (m_g * m_K1 / (2_prt*powi<2>(m_rc)) + (1_prt+powi<2>(sin_psi))*m_g*m_K2/powi<2>(m_rc));
            m_c8_times_1plusdelta = (1_prt/6_prt) * powi<3>(tan_psi) / (2_prt * powi<2>(m_rc));
            m_c9_times_1plusdelta = 0.5_prt * tan_psi * powi<2>(sec_psi) / (2_prt * powi<2>(m_rc));
            m_c10_times_1plusdelta = loc * powi<2>(tan_psi) / (2_prt * m_rc);
            m_c11_times_1plusdelta = loc * 1_prt / (2_prt * m_rc);
            m_c12_times_1plusdelta = (m_g > 0_prt) ? 1_prt / (24_prt) * (4_prt/cos_psi - 8_prt/(powi<3>(cos_psi))) * m_K3/(powi<2>(m_rc) * m_g) : 0_prt;
            m_c13 = powi<2>(sin_psi) / (2_prt*powi<3>(cos_psi)) * powi<2>(m_g)/(m_rc*m_R) * m_K4;
            m_c14 = 0.5_prt * sin_psi/(powi<3>(cos_psi)) * m_g/(m_rc*m_R) * m_K5;
            m_c15 = (m_K6 / (m_rc*m_R)) / (powi<3>(cos_psi));
        }

        template<typename T_Real=amrex::ParticleReal, typename T_IdCpu=uint64_t>
        AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
        void operator() (
            T_Real & AMREX_RESTRICT x,
            T_Real & AMREX_RESTRICT y,
            [[maybe_unused]] T_Real & AMREX_RESTRICT t,
            T_Real & AMREX_RESTRICT px,
            T_Real & AMREX_RESTRICT py,
            [[maybe_unused]] T_Real & AMREX_RESTRICT pt,
            [[maybe_unused]] T_IdCpu & 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)
            using amrex::Math::powi;
 
            // shift due to alignment errors of the element
            shift_in(x, y, px, py);
 
            if (m_model == dipedge::Model::linear) {
               // apply linear model
               px = px + m_R21 * x;
               py = py + m_R43 * y;
            } else {
               // apply nonlinear model
               T_Real xout = x;
               T_Real pxout = px;
               T_Real yout = y;
               T_Real pyout = py;
               T_Real tout = t;
               T_Real ptout = pt;
 
               // compute particle momentum deviation delta + 1 (reciprocal)
               T_Real const inv_delta1 = 1_prt / sqrt(1_prt - 2_prt*pt/m_beta + powi<2>(pt));
 
               T_Real const c2 = m_c2_times_1plusdelta * inv_delta1;
               T_Real const c3 = m_c3_times_1plusdelta * inv_delta1;
               //T_Real const c4 = m_c4_times_1plusdelta * inv_delta1; //not currently used
               //T_Real const c6 = m_c6_times_1plusdelta * inv_delta1; //not currently used
               T_Real const c7 = m_c7_times_1plusdelta * inv_delta1;
               T_Real const c8 = m_c8_times_1plusdelta * inv_delta1;
               T_Real const c9 = m_c9_times_1plusdelta * inv_delta1;
               T_Real const c10 = m_c10_times_1plusdelta * inv_delta1;
               T_Real const c11 = m_c11_times_1plusdelta * inv_delta1;
               T_Real const c12 = m_c12_times_1plusdelta * inv_delta1;
 
               // update transverse coordinates
               xout = x - c3 - c10*powi<2>(x) + (c10 + c11)*powi<2>(y);
               yout = y + 2_prt * c10 * x * y;
 
               // update transverse momenta
               T_Real const D = 1_prt - 4_prt*c10*c11*powi<2>(y) - 4_prt*powi<2>(c10)*(powi<2>(x)+powi<2>(y));
               T_Real const dRdx = -m_c13 + c2 + c3*m_c5 + 2_prt*(m_c14 - m_c5)*x + 3_prt*(m_c15/6_prt + c10*m_c5 + c8)*powi<2>(x)
                                   + (-m_c15/2_prt + c10*m_c5 - c11*m_c5 - c9)*powi<2>(y);
               T_Real const dRdy = 2_prt*(-m_c14 + m_c5 - c7)*y + 2_prt*(-m_c15/2_prt + c10*m_c5 - c11*m_c5 - c9)*x*y - 4_prt*c12*powi<3>(y);
               T_Real const dXdx = 1_prt - 2_prt*c10*x;
               T_Real const dXdy = 2_prt*(c10 + c11)*y;
               T_Real const dYdx = 2_prt*c10*y;
               T_Real const dYdy = 1_prt + 2_prt*c10*x;
 
               pxout = (dYdy * (px - dRdx) - dYdx * (py - dRdy)) / D;
               pyout = (-dXdy * (px - dRdx) + dXdx * (py - dRdy)) / D;
 
               // update temporal coordinate
               T_Real const dDelta_dpt = (pt - 1_prt/m_beta) * inv_delta1;
               tout = t - dDelta_dpt * inv_delta1 * ((c2 + c3*m_c5)*x + (c10*m_c5 + c8)*powi<3>(x) - c7*powi<2>(y) - c12*powi<4>(y)
                      + (c10*m_c5 - c11*m_c5 - c9)*x*powi<2>(y) + pxout*(-c3 + (c11 + c10)*powi<2>(y) - c10*powi<2>(x)) + 2_prt*pyout*c10*x*y);
 
               // optional removal of reference particle shift
               amrex::ParticleReal const c2_ref = m_c2_times_1plusdelta;
               amrex::ParticleReal const c3_ref = m_c3_times_1plusdelta;
               T_Real const dx_ref = (m_modify_ref_part) ? -c3_ref : 0_prt;
               T_Real const dpx_ref = (m_modify_ref_part) ? m_c13 - c2_ref - c3_ref*m_c5 : 0_prt;
               T_Real const dt_ref = -c3_ref * dpx_ref / m_beta;
               xout -= dx_ref;
               pxout -= dpx_ref;
               tout -= dt_ref;
 
               x = xout;
               px = pxout;
               y = yout;
               py = pyout;
               t = tout;
               pt = ptout;
            }
 
            // undo shift due to alignment errors of the element
            shift_out(x, y, px, py);
        }
 

        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
            [[maybe_unused]] amrex::ParticleReal const x = refpart.x;
            [[maybe_unused]] amrex::ParticleReal const z = refpart.z;
            [[maybe_unused]] amrex::ParticleReal const t = refpart.t;
            [[maybe_unused]] amrex::ParticleReal const px = refpart.px;
            [[maybe_unused]] amrex::ParticleReal const pz = refpart.pz;
            [[maybe_unused]] amrex::ParticleReal const pt = refpart.pt;
 
            if (m_modify_ref_part && m_model == dipedge::Model::nonlinear) {
                // calculate expensive terms
                amrex::ParticleReal const loc = m_location == dipedge::Location::entry ? 1_prt : -1_prt;
                auto const [sin_psi, cos_psi] = amrex::Math::sincos(m_psi);
                amrex::ParticleReal const tan_psi = sin_psi/cos_psi;
                amrex::ParticleReal const sec_psi = 1_prt/cos_psi;
                amrex::ParticleReal const c2_ref = powi<2>(m_g/m_rc) * m_K0 * sin_psi * powi<3>(sec_psi)/2_prt;
                amrex::ParticleReal const c3_ref = loc * powi<2>(m_g)/m_rc * m_K0 * powi<2>(sec_psi);
                amrex::ParticleReal const c5_ref = tan_psi / (2_prt * m_rc);
                amrex::ParticleReal const c13_ref = powi<2>(sin_psi) / (2_prt*powi<3>(cos_psi)) * powi<2>(m_g)/(m_rc*m_R) * m_K4;
 
                amrex::ParticleReal const pnorm = std::sqrt(pt*pt-1_prt);
                amrex::ParticleReal const dx_ref = -c3_ref;
                amrex::ParticleReal const dpx_ref = c13_ref - c2_ref - c3_ref*c5_ref;
                amrex::ParticleReal const dpz_ref = pnorm*(-1_prt + std::sqrt(1_prt - powi<2>(dpx_ref/pnorm)));
                amrex::ParticleReal const dt_ref = -c3_ref * dpx_ref / refpart.beta();
 
                // advance position and momentum
                refpart.x = x + (pz/pnorm)*dx_ref;
                refpart.z = z - (px/pnorm)*dx_ref;
                refpart.t = t + dt_ref;
                refpart.px = px + (pz/pnorm)*dpx_ref + (px/pnorm)*dpz_ref;
                refpart.pz = pz - (px/pnorm)*dpx_ref + (pz/pnorm)*dpz_ref;
                // refpart.pt = pt;  // Unchanged
            }
 
        }
 

        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;
 
            // initialize linear map matrix elements
            Map6x6 R = Map6x6::Identity();
 
            // edge focusing matrix elements (zero gap)
            amrex::ParticleReal const R21 = std::tan(m_psi) / m_rc;
 
            // first-order effect of nonzero gap
            auto const [sin_psi, cos_psi] = amrex::Math::sincos(m_psi);
            amrex::ParticleReal const vf = (1.0_prt + powi<2>(sin_psi))
                / powi<3>(cos_psi)
                * m_g * m_K2 / powi<2>(m_rc);
 
            amrex::ParticleReal const R43 = vf - R21;
 
            // set non-identity matrix elements
            R(2,1) = R21;
            R(4,3) = R43;
 
            return R;
        }
 
        amrex::ParticleReal m_psi; 
        amrex::ParticleReal m_rc; 
        amrex::ParticleReal m_g; 
        amrex::ParticleReal m_R; 
        amrex::ParticleReal m_K0; 
        amrex::ParticleReal m_K1; 
        amrex::ParticleReal m_K2; 
        amrex::ParticleReal m_K3; 
        amrex::ParticleReal m_K4; 
        amrex::ParticleReal m_K5; 
        amrex::ParticleReal m_K6; 
        dipedge::Model m_model; 
        dipedge::Location m_location; 
        bool m_modify_ref_part; 
 
      private:
        // constants that are independent of the individually tracked particle,
        // see: compute_constants() to refresh
        amrex::ParticleReal m_R21, m_R43, m_beta;
        amrex::ParticleReal m_c1, m_c5, m_c13, m_c14, m_c15;
        amrex::ParticleReal m_c2_times_1plusdelta, m_c3_times_1plusdelta, m_c4_times_1plusdelta, m_c6_times_1plusdelta;
        amrex::ParticleReal m_c7_times_1plusdelta, m_c8_times_1plusdelta, m_c9_times_1plusdelta, m_c10_times_1plusdelta;
        amrex::ParticleReal m_c11_times_1plusdelta, m_c12_times_1plusdelta;
    };
 
} // namespace impactx
 
IMPACTX_PUSH_EXTERN_TEMPLATE(impactx::elements::DipEdge)
 
#endif // IMPACTX_DIPEDGE_H