ImpactX
ExactDrift.H
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1 /* Copyright 2022-2023 The Regents of the University of California, through Lawrence
2  * Berkeley National Laboratory (subject to receipt of any required
3  * approvals from the U.S. Dept. of Energy). All rights reserved.
4  *
5  * This file is part of ImpactX.
6  *
7  * Authors: Chad Mitchell, Axel Huebl
8  * License: BSD-3-Clause-LBNL
9  */
10 #ifndef IMPACTX_EXACTDRIFT_H
11 #define IMPACTX_EXACTDRIFT_H
12 
14 #include "mixin/beamoptic.H"
15 #include "mixin/thick.H"
16 #include "mixin/nofinalize.H"
17 
18 #include <AMReX_Extension.H>
19 #include <AMReX_REAL.H>
20 
21 #include <cmath>
22 
23 
24 namespace impactx
25 {
26  struct ExactDrift
27  : public elements::BeamOptic<ExactDrift>,
28  public elements::Thick,
30  {
31  static constexpr auto name = "ExactDrift";
33 
39  ExactDrift( amrex::ParticleReal const ds, int const nslice )
40  : Thick(ds, nslice)
41  {
42  }
43 
45  using BeamOptic::operator();
46 
58  PType& AMREX_RESTRICT p,
59  amrex::ParticleReal & AMREX_RESTRICT px,
60  amrex::ParticleReal & AMREX_RESTRICT py,
61  amrex::ParticleReal & AMREX_RESTRICT pt,
62  RefPart const & refpart) const {
63 
64  using namespace amrex::literals; // for _rt and _prt
65 
66  // access AoS data such as positions and cpu/id
67  amrex::ParticleReal const x = p.pos(RealAoS::x);
68  amrex::ParticleReal const y = p.pos(RealAoS::y);
69  amrex::ParticleReal const t = p.pos(RealAoS::t);
70 
71  // initialize output values of momenta
72  amrex::ParticleReal const pxout = px;
73  amrex::ParticleReal const pyout = py;
74  amrex::ParticleReal const ptout = pt;
75 
76  // length of the current slice
77  amrex::ParticleReal const slice_ds = m_ds / nslice();
78 
79  // access reference particle values to find beta, beta*gamma
80  amrex::ParticleReal const bet = refpart.beta();
81  amrex::ParticleReal const betgam = refpart.beta_gamma();
82 
83  // compute the radical in the denominator (= pz):
84  amrex::ParticleReal const pzden = sqrt(pow(pt-1_prt/bet,2) -
85  1_prt/pow(betgam,2) - pow(px,2) - pow(py,2));
86 
87  // advance position and momentum (exact drift)
88  p.pos(RealAoS::x) = x + slice_ds * px / pzden;
89  // pxout = px;
90  p.pos(RealAoS::y) = y + slice_ds * py / pzden;
91  // pyout = py;
92  p.pos(RealAoS::t) = t - slice_ds * (1_prt/bet +
93  (pt-1_prt/bet)/pzden);
94  // ptout = pt;
95 
96  // assign updated momenta
97  px = pxout;
98  py = pyout;
99  pt = ptout;
100 
101  }
102 
108  void operator() (RefPart & AMREX_RESTRICT refpart) const {
109 
110  using namespace amrex::literals; // for _rt and _prt
111 
112  // assign input reference particle values
113  amrex::ParticleReal const x = refpart.x;
114  amrex::ParticleReal const px = refpart.px;
115  amrex::ParticleReal const y = refpart.y;
116  amrex::ParticleReal const py = refpart.py;
117  amrex::ParticleReal const z = refpart.z;
118  amrex::ParticleReal const pz = refpart.pz;
119  amrex::ParticleReal const t = refpart.t;
120  amrex::ParticleReal const pt = refpart.pt;
121  amrex::ParticleReal const s = refpart.s;
122 
123  // length of the current slice
124  amrex::ParticleReal const slice_ds = m_ds / nslice();
125 
126  // assign intermediate parameter
127  amrex::ParticleReal const step = slice_ds / sqrt(pow(pt,2)-1.0_prt);
128 
129  // advance position and momentum (drift)
130  refpart.x = x + step*px;
131  refpart.y = y + step*py;
132  refpart.z = z + step*pz;
133  refpart.t = t - step*pt;
134 
135  // advance integrated path length
136  refpart.s = s + slice_ds;
137 
138  }
139  };
140 
141 } // namespace impactx
142 
143 #endif // IMPACTX_EXACTDRIFT_H
#define AMREX_FORCE_INLINE
#define AMREX_GPU_HOST_DEVICE
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE GpuComplex< T > pow(const GpuComplex< T > &a_z, const T &a_y) noexcept
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE GpuComplex< T > sqrt(const GpuComplex< T > &a_z) noexcept
Definition: ImpactX.cpp:33
s
Definition: ExactDrift.H:30
static constexpr auto name
Definition: ExactDrift.H:31
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE void operator()(PType &AMREX_RESTRICT p, amrex::ParticleReal &AMREX_RESTRICT px, amrex::ParticleReal &AMREX_RESTRICT py, amrex::ParticleReal &AMREX_RESTRICT pt, RefPart const &refpart) const
Definition: ExactDrift.H:57
ExactDrift(amrex::ParticleReal const ds, int const nslice)
Definition: ExactDrift.H:39
ImpactXParticleContainer::ParticleType PType
Definition: ExactDrift.H:32
@ x
position in x [m] (at fixed s OR fixed t)
Definition: ImpactXParticleContainer.H:42
@ y
position in y [m] (at fixed s OR fixed t)
Definition: ImpactXParticleContainer.H:43
@ t
c * time-of-flight [m] (at fixed s)
Definition: ImpactXParticleContainer.H:44
Definition: ReferenceParticle.H:30
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::ParticleReal beta_gamma() const
Definition: ReferenceParticle.H:79
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::ParticleReal beta() const
Definition: ReferenceParticle.H:64
Definition: beamoptic.H:135
Definition: nofinalize.H:22
Definition: thick.H:24
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE amrex::ParticleReal ds() const
Definition: thick.H:50
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE int nslice() const
Definition: thick.H:40
amrex::ParticleReal m_ds
Definition: thick.H:56
Thick(amrex::ParticleReal const ds, int const nslice)
Definition: thick.H:30