# spectral_density_lite

plasmapy.diagnostics.thomson.spectral_density_lite(wavelengths, probe_wavelength: Real, n: Real, T_e: ndarray, T_i: ndarray, efract: ndarray, ifract: ndarray, ion_z: ndarray, ion_mass: ndarray, electron_vel: ndarray, ion_vel: ndarray, probe_vec: ndarray, scatter_vec: ndarray, instr_func_arr: = None)

The lite-function version of spectral_density. Performs the same thermal speed calculations as spectral_density, but is intended for computational use and thus has data conditioning safeguards removed.

Parameters
• wavelengths ((Nλ,) ndarray) – The wavelengths in meters over which the spectral density function will be calculated.

• probe_wavelength (real number) – Wavelength of the probe laser in meters.

• n (ndarray) – Total combined number density of all electron populations in m-3.

• T_e ((Ne,) ndarray) – Temperature of each electron population in kelvin, where Ne is the number of electron populations.

• T_i ((Ni,) ndarray) – Temperature of each ion population in kelvin, where Ni is the number of ion populations.

• efract ((Ne,) ndarray) – An ndarray where each element represents the fraction (or ratio) of the electron population number density to the total electron number density. Must sum to 1.0. Default is a single electron population.

• ifract ((Ni,) ndarray) – An ndarray object where each element represents the fraction (or ratio) of the ion population number density to the total ion number density. Must sum to 1.0. Default is a single ion species.

• ion_z ((Ni,) ndarray) – An ndarray of the charge number $$Z$$ of each ion species.

• ion_mass ((Ni,) ndarray) – An ndarray of the mass of each ion species in kg.

• electron_vel ((Ne, 3) ndarray) – Velocity of each electron population in the rest frame (in m/s). If set, overrides electron_vdir and electron_speed. Defaults to a stationary plasma [0, 0, 0] m/s.

• ion_vel ((Ni, 3) ndarray) – Velocity vectors for each electron population in the rest frame (in m/s). If set, overrides ion_vdir and ion_speed. Defaults to zero drift for all specified ion species.

• probe_vec ((3,) float ndarray) – Unit vector in the direction of the probe laser. Defaults to [1, 0, 0].

• scatter_vec ((3,) float ndarray) – Unit vector pointing from the scattering volume to the detector. Defaults to [0, 1, 0] which, along with the default probe_vec, corresponds to a 90 degree scattering angle geometry.

• instr_func_arr (ndarray, shape (Nwavelengths,) optional) –

The instrument function evaluated at a linearly spaced range of wavelengths ranging from $$-W$$ to $$W$$, where

$W = 0.5*(\max{λ} - \min{λ})$

Here $$λ$$ is the wavelengths array. This array will be convolved with the spectral density function before it is returned.

Returns

• alpha (float) – Mean scattering parameter, where alpha > 1 corresponds to collective scattering and alpha < 1 indicates non-collective scattering. The scattering parameter is calculated based on the total plasma density $$n$$.

• Skw (ndarray) – Computed spectral density function over the input wavelengths array with units of s/rad.