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#!/usr/bin/env python3
# Copyright 2019-2020 Luca Fedeli, Maxence Thevenet
#
# This file is part of WarpX.
#
# License: BSD-3-Clause-LBNL
'''
Analysis script of a WarpX simulation of rigid injection.
A Gaussian electron beam starts from -5 microns, propagates rigidly up to
20 microns after which it expands due to emittance only (the focal position is
20 microns). The beam width is measured after ~50 microns, and compared with
the theory (with a 5% error allowed).
As a help to the user, the script also compares beam width to the theory in
case rigid injection is OFF (i.e., the beam starts expanding from -5 microns),
in which case a warning is raised.
'''
import sys
import yt
import numpy as np
import os
yt.funcs.mylog.setLevel(0)
sys.path.insert(1, '../../../../warpx/Regression/Checksum/')
import checksumAPI
filename = sys.argv[1]
# WarpX headers include more data when rigid injection is used,
# which gives an error with the last yt release.
# To avoid this issue, the three last lines of WarpXHeader are removed if
# needed.
def remove_rigid_lines(plotfile, nlines_if_rigid):
header_name = plotfile + '/WarpXHeader'
f = open(header_name, 'r')
file_lines = f.readlines()
nlines = len(file_lines)
f.close()
if nlines == nlines_if_rigid:
f = open(header_name, 'w')
f.writelines(file_lines[:-3])
f.close()
# Remove rigid injection header lines
remove_rigid_lines(filename, 18)
# Read beam parameters
ds = yt.load( filename )
ad = ds.all_data()
# Beam longitudinal position
z = np.mean(ad['beam', 'particle_position_y'].v)
# Beam width
w = np.std(ad['beam', 'particle_position_x'].v)
# initial parameters
z0 = 20.e-6
z0_no_rigid = -5.e-6
w0 = 1.e-6
theta0 = np.arcsin(0.1)
# Theoretical beam width after propagation if rigid OFF
# Inform the user if rigid injection simply off (just to be kind)
wth_no_rigid = np.sqrt( w0**2 + (z-z0_no_rigid)**2*theta0**2 )
error_no_rigid = np.abs((w-wth_no_rigid)/wth_no_rigid)
if ( error_no_rigid < 0.05):
print("error no rigid: " + str(error_no_rigid))
print("Looks like the beam defocuses as if rigid injection were OFF")
# Theoretical beam width after propagation if rigid ON
wth = np.sqrt( w0**2 + (z-z0)**2*theta0**2 )
error_rel = np.abs((w-wth)/wth)
tolerance_rel = 0.05
# Print error and assert small error
print("Beam position: " + str(z))
print("Beam width : " + str(w))
print("error_rel : " + str(error_rel))
print("tolerance_rel: " + str(tolerance_rel))
assert( error_rel < tolerance_rel )
test_name = os.path.split(os.getcwd())[1]
checksumAPI.evaluate_checksum(test_name, filename)
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