PICMI_inputs_reflection.py

#!/usr/bin/env python3
#
# --- Input file to test particle reflection off an absorbing boundary

from pywarpx import particle_containers, picmi

constants = picmi.constants

##########################
# numerics parameters
##########################

dt = 7.5e-12

# --- Nb time steps

max_steps = 10

# --- grid

nx = 64
nz = 64

xmin = -125e-6
zmin = -149e-6
xmax = 125e-6
zmax = 1e-6


##########################
# numerics components
##########################

grid = picmi.Cartesian2DGrid(
    number_of_cells = [nx, nz],
    lower_bound = [xmin, zmin],
    upper_bound = [xmax, zmax],
    lower_boundary_conditions = ['dirichlet', 'dirichlet'],
    upper_boundary_conditions = ['dirichlet', 'dirichlet'],
    lower_boundary_conditions_particles = ['open', 'absorbing'],
    upper_boundary_conditions_particles = ['open', 'absorbing'],
    warpx_max_grid_size = 32
)

solver = picmi.ElectrostaticSolver(
    grid=grid, method='Multigrid', required_precision=1e-6,
    warpx_self_fields_verbosity=0
)

#embedded_boundary = picmi.EmbeddedBoundary(
#    implicit_function="-max(max(x-12.5e-6,-12.5e-6-x),max(z+6.15e-5,-8.65e-5-z))"
#)

##########################
# physics components
##########################

uniform_plasma_elec = picmi.UniformDistribution(
    density = 1e15, # number of electrons per m^3
    lower_bound = [-1e-5, -1e-5, -125e-6],
    upper_bound = [1e-5, 1e-5, -120e-6],
    directed_velocity = [0., 0., 5e6] # uth the std of the (unitless) momentum
)

electrons = picmi.Species(
    particle_type='electron', name='electrons',
    initial_distribution=uniform_plasma_elec,
    warpx_save_particles_at_zhi=1,
    warpx_save_particles_at_zlo=1,
    warpx_reflection_model_zhi="0.5"
)

##########################
# diagnostics
##########################

particle_diag = picmi.ParticleDiagnostic(
    name = 'diag1',
    period = 10,
    write_dir = '.',
    warpx_file_prefix = 'Python_particle_reflection_plt'
)
field_diag = picmi.FieldDiagnostic(
    grid=grid,
    name = 'diag1',
    data_list=['E'],
    period = 10,
    write_dir = '.',
    warpx_file_prefix = 'Python_particle_reflection_plt'
)

##########################
# simulation setup
##########################

sim = picmi.Simulation(
    solver = solver,
    time_step_size = dt,
    max_steps = max_steps,
    # warpx_embedded_boundary=embedded_boundary,
    verbose = 1
)

sim.add_species(
    electrons,
    layout = picmi.GriddedLayout(
        n_macroparticle_per_cell=[5, 2], grid=grid
    )
)
sim.add_diagnostic(particle_diag)
sim.add_diagnostic(field_diag)

##########################
# simulation run
##########################

sim.step(max_steps)

################################################
# check that the wrappers to access the particle
# buffer functions as intended
################################################

buffer = particle_containers.ParticleBoundaryBufferWrapper()

n = buffer.get_particle_boundary_buffer_size("electrons", 'z_hi')
print("Number of electrons in upper buffer:", n)
assert n == 63

n = buffer.get_particle_boundary_buffer_size("electrons", 'z_lo')
print("Number of electrons in lower buffer:", n)
assert n == 67

scraped_steps = buffer.get_particle_boundary_buffer("electrons", 'z_hi', 'stepScraped', 0)
for arr in scraped_steps:
    # print(arr)
    assert all(arr == 4)

scraped_steps = buffer.get_particle_boundary_buffer("electrons", 'z_lo', 'stepScraped', 0)
for arr in scraped_steps:
    # print(arr)
    assert all(arr == 8)