# Source code for pyMETHES.gas_mixture

```
# Copyright (c) 2020-2021 ETH Zurich
"""
Module for the GasMixture class, which aggregates data of different gases.
The GasMixture uses the cross_section module to read cross section data. It stores
linear interpolations of each cross section, as well as the mass ratio,
energy threshold and type of cross section, which are needed for the simulation.
The proportions of the gas mixture should sum up to 1. A common energy_vector for all
cross sections is calculated, as well as the total_cross_section.
"""
# Import Packages
import numpy as np
from lxcat_data_parser import CrossSectionTypes as CST
import scipy.interpolate
# Import modules
from pyMETHES.cross_section import InterpolatedCrossSectionSet
np.seterr(all='raise')
[docs]class GasMixture:
"""
Class representing a gas mixture.
Attributes:
cross_sections (ndarray): array of cross section interpolations (from all gases)
types (ndarray): type of each cross section of each species
thresholds (ndarray): threshold of each cross section of each species
mass_ratios (ndarray): mass ratios (repeated for each cross section)
is_attachment (ndarray): boolean mask for ATTACHMENT cross sections
is_ionization (ndarray): boolean mask for IONIZATION cross sections
energy_vector (ndarray): common energy vector, containing all distinct energies
of all cross sections
total_cross_section (ndarray): sum of all cross sections of all species,
linearly interpolated at energy_vector
"""
[docs] def __init__(self, gas_formulas: list, path_to_cross_section_files: list,
proportions: list, max_cross_section_energy: float):
"""
Instantiates a GasMixture.
Args:
gas_formulas (list): list of the chemical formulas of the species
path_to_cross_section_files (list): path to the cross section data of each
species
proportions (list): proportion of each species in the mixture
max_cross_section_energy (float): maximum cross section energy (eV)
Raises:
ValueError: If the proportions do not sum up to 1
"""
# check if the sum of proportions is 1
if not np.isclose(sum(proportions), 1):
raise ValueError("The sum of the proportions of the gases in the GasMixture"
"must be 1, but it is %1.2f" % (sum(proportions)))
# Create a list with a Gas Object for each gas of the mixture
gases = [InterpolatedCrossSectionSet(max_cross_section_energy, *args)
for args in zip(path_to_cross_section_files, gas_formulas)]
self.cross_sections = np.array([
scipy.interpolate.interp1d(x.data['energy'].to_numpy(),
x.data['cross section'].to_numpy() * p,
kind='linear')
for p, gas in zip(proportions, gases) for x in gas.cross_sections
])
cross_sections = [x for gas in gases for x in gas.cross_sections]
self.thresholds = np.asarray([x.threshold for x in cross_sections])
self.mass_ratios = np.asarray([x.mass_ratio for x in cross_sections])
self.types = [x.type for x in cross_sections]
types_array = np.asarray(self.types)
self.is_attachment = types_array == CST.ATTACHMENT
self.is_ionization = types_array == CST.IONIZATION
# combine the energy vectors into a total energy vector
all_energies = np.concatenate([x.data['energy'] for x in cross_sections])
self.energy_vector = np.unique(all_energies)
# calculate the total cross section
self.total_cross_section = \
np.sum([interp(self.energy_vector) for interp in self.cross_sections],
axis=0)
@property
def number_of_cross_sections(self) -> int:
"""
int: Total number of cross sections, all gases considered.
"""
return self.cross_sections.size
```