The ionization state (or charge state) of a plasma refers to the fraction of an element that is at each ionization level. For example, the ionization state of a pure helium plasma could be 5% He0+, 94% He1+, and 1% He2+.
We may use the class to represent the ionization state of a single element, such as for this example.
>>> from plasmapy.particles import IonizationState >>> ionization_state = IonizationState("He", [0.05, 0.94, 0.01])
Ionization state information for helium may be accessed using the ~plasmapy.particles.ionization_state.IonizationState.ionic_fractions attribute. These ionic fractions correspond to the ~plasmapy.particles.ionization_state.IonizationState.charge_numbers attribute.
>>> ionization_state.ionic_fractions array([0.05, 0.94, 0.01]) >>> ionization_state.charge_numbers array([0, 1, 2])
The ~plasmapy.particles.ionization_state.IonizationState.Z_mean attribute returns the mean charge number averaged over all particles in that element.
>>> ionization_state.Z_mean 0.96
The ~plasmapy.particles.ionization_state.IonizationState.Z_rms attribute returns the root mean square charge number.
>>> ionization_state.Z_rms 0.9899...
The ~plasmapy.particles.ionization_state.IonizationState.Z_most_abundant attribute returns a list of the most abundant ion(s). The list may contain more than one charge number in case of a tie.
>>> ionization_state.Z_most_abundant [1]
The ~plasmapy.particles.ionization_state.IonizationState.summarize method prints out the ionic fraction for the ions with an abundance of at least 1%.
>>> ionization_state.summarize() IonizationState instance for He with Z_mean = 0.96 ----------------------------------------------------------------He 0+: 0.050 He 1+: 0.940 He 2+: 0.010 ----------------------------------------------------------------
The number density of the element may be specified through the n_elem keyword argument.
>>> import astropy.units as u >>> ionization_state = IonizationState( ... "He", [0.05, 0.94, 0.01], n_elem = 1e19 * u.m ** -3, ... )
The ~plasmapy.particles.ionization_state.IonizationState.n_e attribute provides the electron number density as a .
>>> ionization_state.n_e <Quantity 9.6e+18 1 / m3>
The ~plasmapy.particles.ionization_state.IonizationState.number_densities attribute provides the number density of each ion or neutral.
>>> ionization_state.number_densities <Quantity [5.0e+17, 9.4e+18, 1.0e+17] 1 / m3>
The class may be used to represent the ionization state for multiple elements. This can be used, for example, to describe the various impurities in a fusion plasma or the charge state distributions of different elements in the solar wind.
>>> from plasmapy.particles import IonizationStateCollection
The minimal input to is a list of the elements or isotopes to represent. Integers in the list will be treated as atomic numbers.
>>> states = IonizationStateCollection(["H", 2])
To set the ionic fractions for hydrogen, we may do item assignment.
>>> states["H"] = [0.9, 0.1]
We may use indexing to retrieve an instance for an element.
>>> states["H"] <IonizationState instance for H>
The ionization states for all of the elements may be specified directly as arguments to the class.
>>> states = IonizationStateCollection( ... {"H": [0.01, 0.99], "He": [0.04, 0.95, 0.01]}, ... abundances={"H": 1, "He": 0.08}, ... n0 = 5e19 * u.m ** -3, ... )
The ionic fractions will be stored as a dict.
>>> states.ionic_fractions {'H': array([0.01, 0.99]), 'He': array([0.04, 0.95, 0.01])}
The number density for each element is the product of the number density scaling factor ~plasmapy.particles.ionization_state_collection.IonizationStateCollection.n0 with that element's abundance. The number density for each ion is the product of ~plasmapy.particles.ionization_state_collection.IonizationStateCollection.n0, the corresponding element's abundance, and the ionic fraction.
>>> states.n <Quantity 5.e+19 1 / m3> >>> states.abundances {'H': 1.0, 'He': 0.08} >>> states.number_densities["H"] <Quantity [5.00e+17, 4.95e+19] 1 / m3>
The ~plasmapy.particles.ionization_state_collection.IonizationStateCollection.summarize method may also be used to summarize the ionization states.
H 1+: 0.990 n_i = 4.95e+19 m*-3 ----------------------------------------------------------------He 0+: 0.040 n_i = 1.60e+17 m-3 He 1+: 0.950 n_i = 3.80e+18 m-3 ----------------------------------------------------------------n_e = 5.34e+19 m*-3 T_e = 1.30e+04 K ----------------------------------------------------------------