WarpX
GetExternalFields.H
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1 #ifndef WARPX_PARTICLES_GATHER_GETEXTERNALFIELDS_H_
2 #define WARPX_PARTICLES_GATHER_GETEXTERNALFIELDS_H_
3 
5 
7 #include "Utils/WarpXConst.H"
8 
10 
11 #include <AMReX.H>
12 #include <AMReX_Array.H>
13 #include <AMReX_Extension.H>
14 #include <AMReX_GpuQualifiers.H>
15 #include <AMReX_Parser.H>
16 #include <AMReX_REAL.H>
17 
18 #include <optional>
19 
20 
25 {
27 
28  GetExternalEBField () = default;
29 
30  GetExternalEBField (const WarpXParIter& a_pti, long a_offset = 0) noexcept;
31 
34 
35  amrex::ParticleReal m_gamma_boost;
36  amrex::ParticleReal m_uz_boost;
37 
38  amrex::ParserExecutor<4> m_Exfield_partparser;
39  amrex::ParserExecutor<4> m_Eyfield_partparser;
40  amrex::ParserExecutor<4> m_Ezfield_partparser;
41  amrex::ParserExecutor<4> m_Bxfield_partparser;
42  amrex::ParserExecutor<4> m_Byfield_partparser;
43  amrex::ParserExecutor<4> m_Bzfield_partparser;
44 
46  amrex::Real m_time;
47 
49  const amrex::ParticleReal* AMREX_RESTRICT m_repeated_plasma_lens_starts = nullptr;
50  const amrex::ParticleReal* AMREX_RESTRICT m_repeated_plasma_lens_lengths = nullptr;
51  const amrex::ParticleReal* AMREX_RESTRICT m_repeated_plasma_lens_strengths_E = nullptr;
52  const amrex::ParticleReal* AMREX_RESTRICT m_repeated_plasma_lens_strengths_B = nullptr;
54  amrex::Real m_dt;
55  const amrex::ParticleReal* AMREX_RESTRICT m_ux = nullptr;
56  const amrex::ParticleReal* AMREX_RESTRICT m_uy = nullptr;
57  const amrex::ParticleReal* AMREX_RESTRICT m_uz = nullptr;
58 
60 
61  [[nodiscard]] AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
62  bool isNoOp () const { return (m_Etype == None && m_Btype == None && !d_lattice_element_finder.has_value()); }
63 
65  void operator () (long i,
66  amrex::ParticleReal& field_Ex,
67  amrex::ParticleReal& field_Ey,
68  amrex::ParticleReal& field_Ez,
69  amrex::ParticleReal& field_Bx,
70  amrex::ParticleReal& field_By,
71  amrex::ParticleReal& field_Bz) const noexcept
72  {
73  using namespace amrex::literals;
74 
76  // Note that the "*" is needed since d_lattice_element_finder is optional
77  (*d_lattice_element_finder)(i, field_Ex, field_Ey, field_Ez,
78  field_Bx, field_By, field_Bz);
79  }
80 
81  if (m_Etype == None && m_Btype == None) { return; }
82 
83  amrex::ParticleReal Ex = 0._prt;
84  amrex::ParticleReal Ey = 0._prt;
85  amrex::ParticleReal Ez = 0._prt;
86  amrex::ParticleReal Bx = 0._prt;
87  amrex::ParticleReal By = 0._prt;
88  amrex::ParticleReal Bz = 0._prt;
89 
90  constexpr amrex::ParticleReal inv_c2 = 1._prt/(PhysConst::c*PhysConst::c);
91 
92  if (m_Etype == ExternalFieldInitType::Parser)
93  {
94  amrex::ParticleReal x, y, z;
95  m_get_position(i, x, y, z);
96  amrex::Real lab_time = m_time;
97  if (m_gamma_boost > 1._prt) {
98  lab_time = m_gamma_boost*m_time + m_uz_boost*z*inv_c2;
100  }
101  Ex = m_Exfield_partparser((amrex::ParticleReal) x, (amrex::ParticleReal) y, (amrex::ParticleReal) z, lab_time);
102  Ey = m_Eyfield_partparser((amrex::ParticleReal) x, (amrex::ParticleReal) y, (amrex::ParticleReal) z, lab_time);
103  Ez = m_Ezfield_partparser((amrex::ParticleReal) x, (amrex::ParticleReal) y, (amrex::ParticleReal) z, lab_time);
104  }
105 
106  if (m_Btype == ExternalFieldInitType::Parser)
107  {
108  amrex::ParticleReal x, y, z;
109  m_get_position(i, x, y, z);
110  amrex::Real lab_time = m_time;
111  if (m_gamma_boost > 1._prt) {
112  lab_time = m_gamma_boost*m_time + m_uz_boost*z*inv_c2;
114  }
115  Bx = m_Bxfield_partparser(x, y, z, lab_time);
116  By = m_Byfield_partparser(x, y, z, lab_time);
117  Bz = m_Bzfield_partparser(x, y, z, lab_time);
118  }
119 
120  if (m_Etype == RepeatedPlasmaLens ||
122  {
123  amrex::ParticleReal x, y, z;
124  m_get_position(i, x, y, z);
125 
126  const amrex::ParticleReal uxp = m_ux[i];
127  const amrex::ParticleReal uyp = m_uy[i];
128  const amrex::ParticleReal uzp = m_uz[i];
129 
130  const amrex::ParticleReal gamma = std::sqrt(1._prt + (uxp*uxp + uyp*uyp + uzp*uzp)*inv_c2);
131  const amrex::ParticleReal vzp = uzp/gamma;
132 
133  // the current slice in z between now and the next time step
134  amrex::ParticleReal zl = z;
135  amrex::ParticleReal zr = z + vzp*m_dt;
136 
137  if (m_gamma_boost > 1._prt) {
138  zl = m_gamma_boost*zl + m_uz_boost*m_time;
139  zr = m_gamma_boost*zr + m_uz_boost*(m_time + m_dt);
140  }
141 
142  // the plasma lens periods do not start before z=0
143  if (zl > 0) {
144  // find which is the next lens
145  const auto i_lens = static_cast<int>(std::floor(zl/m_repeated_plasma_lens_period));
146  if (i_lens < m_n_lenses) {
147  amrex::ParticleReal const lens_start = m_repeated_plasma_lens_starts[i_lens] + i_lens*m_repeated_plasma_lens_period;
148  amrex::ParticleReal const lens_end = lens_start + m_repeated_plasma_lens_lengths[i_lens];
149 
150  // Calculate the residence correction
151  // frac will be 1 if the step is completely inside the lens, between 0 and 1
152  // when entering or leaving the lens, and otherwise 0.
153  // This accounts for the case when particles step over the element without landing in it.
154  // This assumes that vzp > 0.
155  amrex::ParticleReal const zl_bounded = std::min(std::max(zl, lens_start), lens_end);
156  amrex::ParticleReal const zr_bounded = std::min(std::max(zr, lens_start), lens_end);
157  amrex::ParticleReal const frac = ((zr - zl) == 0._rt ? 1._rt : (zr_bounded - zl_bounded)/(zr - zl));
158 
159  // Note that "+=" is used since the fields may have been set above
160  // if a different E or Btype was specified.
161  Ex += x*frac*m_repeated_plasma_lens_strengths_E[i_lens];
162  Ey += y*frac*m_repeated_plasma_lens_strengths_E[i_lens];
163  Bx += +y*frac*m_repeated_plasma_lens_strengths_B[i_lens];
164  By += -x*frac*m_repeated_plasma_lens_strengths_B[i_lens];
165  }
166  }
167 
168  }
169 
170  if (m_gamma_boost > 1._prt) {
171  // Transform the fields to the boosted frame
172  const amrex::ParticleReal Ex_boost = m_gamma_boost*Ex - m_uz_boost*By;
173  const amrex::ParticleReal Ey_boost = m_gamma_boost*Ey + m_uz_boost*Bx;
174  const amrex::ParticleReal Bx_boost = m_gamma_boost*Bx + m_uz_boost*Ey*inv_c2;
175  const amrex::ParticleReal By_boost = m_gamma_boost*By - m_uz_boost*Ex*inv_c2;
176  Ex = Ex_boost;
177  Ey = Ey_boost;
178  Bx = Bx_boost;
179  By = By_boost;
180  }
181 
182  field_Ex += Ex;
183  field_Ey += Ey;
184  field_Ez += Ez;
185  field_Bx += Bx;
186  field_By += By;
187  field_Bz += Bz;
188 
189  }
190 };
191 
192 #endif
#define AMREX_FORCE_INLINE
#define AMREX_GPU_HOST_DEVICE
Definition: WarpXParticleContainer.H:53
static constexpr auto c
vacuum speed of light [m/s]
Definition: constant.H:44
i
Definition: check_interp_points_and_weights.py:174
int gamma
boosted frame
Definition: stencil.py:431
Functor class that assigns external field values (E and B) to particles.
Definition: GetExternalFields.H:25
const amrex::ParticleReal *AMREX_RESTRICT m_repeated_plasma_lens_lengths
Definition: GetExternalFields.H:50
const amrex::ParticleReal *AMREX_RESTRICT m_ux
Definition: GetExternalFields.H:55
amrex::ParserExecutor< 4 > m_Bzfield_partparser
Definition: GetExternalFields.H:43
const amrex::ParticleReal *AMREX_RESTRICT m_uy
Definition: GetExternalFields.H:56
amrex::Real m_time
Definition: GetExternalFields.H:46
const amrex::ParticleReal *AMREX_RESTRICT m_repeated_plasma_lens_strengths_B
Definition: GetExternalFields.H:52
amrex::Real m_dt
Definition: GetExternalFields.H:54
GetExternalEBField()=default
amrex::ParticleReal m_uz_boost
Definition: GetExternalFields.H:36
amrex::ParticleReal m_gamma_boost
Definition: GetExternalFields.H:35
int m_n_lenses
Definition: GetExternalFields.H:53
ExternalFieldInitType m_Etype
Definition: GetExternalFields.H:32
std::optional< LatticeElementFinderDevice > d_lattice_element_finder
Definition: GetExternalFields.H:59
GetParticlePosition< PIdx > m_get_position
Definition: GetExternalFields.H:45
ExternalFieldInitType
Definition: GetExternalFields.H:26
@ Parser
Definition: GetExternalFields.H:26
@ Unknown
Definition: GetExternalFields.H:26
@ None
Definition: GetExternalFields.H:26
@ RepeatedPlasmaLens
Definition: GetExternalFields.H:26
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE void operator()(long i, amrex::ParticleReal &field_Ex, amrex::ParticleReal &field_Ey, amrex::ParticleReal &field_Ez, amrex::ParticleReal &field_Bx, amrex::ParticleReal &field_By, amrex::ParticleReal &field_Bz) const noexcept
Definition: GetExternalFields.H:65
ExternalFieldInitType m_Btype
Definition: GetExternalFields.H:33
amrex::ParserExecutor< 4 > m_Exfield_partparser
Definition: GetExternalFields.H:38
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE bool isNoOp() const
Definition: GetExternalFields.H:62
amrex::ParticleReal m_repeated_plasma_lens_period
Definition: GetExternalFields.H:48
amrex::ParserExecutor< 4 > m_Bxfield_partparser
Definition: GetExternalFields.H:41
const amrex::ParticleReal *AMREX_RESTRICT m_uz
Definition: GetExternalFields.H:57
const amrex::ParticleReal *AMREX_RESTRICT m_repeated_plasma_lens_strengths_E
Definition: GetExternalFields.H:51
const amrex::ParticleReal *AMREX_RESTRICT m_repeated_plasma_lens_starts
Definition: GetExternalFields.H:49
amrex::ParserExecutor< 4 > m_Byfield_partparser
Definition: GetExternalFields.H:42
amrex::ParserExecutor< 4 > m_Ezfield_partparser
Definition: GetExternalFields.H:40
amrex::ParserExecutor< 4 > m_Eyfield_partparser
Definition: GetExternalFields.H:39
Functor that can be used to extract the positions of the macroparticles inside a ParallelFor kernel.
Definition: GetAndSetPosition.H:63
The lattice element finder class that can be trivially copied to the device. This only has simple dat...
Definition: LatticeElementFinder.H:100
Definition: NamedComponentParticleContainer.H:24