6.4. Gaunt factors

This includes classes for temperature-averaged Gaunt factors used to calculate Bremsstrahlung (free-free Gaunt factor) and radiative recombination continuum (bound-free Gaunt factor) emission.

6.4.1. Free-free Gaunt factors

class cherab.core.atomic.gaunt.FreeFreeGauntFactor

The base class for temperature-averaged free-free Gaunt factors.

__call__()

Returns the temperature-averaged free-free Gaunt factor for the supplied parameters.

Parameters:

  • z (double) – Species charge or effective plasma charge.

  • temperature (double) – Electron temperature in eV.

  • wavelength (double) – Spectral wavelength.

Returns:

free-free Gaunt factor

evaluate(z, temperature, wavelength)

Returns the temperature-averaged free-free Gaunt factor for the supplied parameters.

Parameters:

  • z (double) – Species charge or effective plasma charge.

  • temperature (double) – Electron temperature in eV.

  • wavelength (double) – Spectral wavelength.

Returns:

free-free Gaunt factor

class cherab.core.atomic.gaunt.InterpolatedFreeFreeGauntFactor

Bases: FreeFreeGauntFactor

The temperature-averaged free-free Gaunt factors interpolated in the space of parameters: \(u = h{\nu}/kT\) and \({\gamma}^{2} = Z^{2}Ry/kT\). See T.R. Carson, 1988, Astron. & Astrophys., 189, 319 for details.

The cubic interpolation in a semi-log space is used.

The Born approximation is used outside the interpolation range.

Parameters:

  • u (object) – A 1D array-like object of real values.

  • gamma2 (object) – A 1D array-like object of real values.

  • gaunt_factor (object) – 2D array-like object of real values storing the Gaunt factor values at u, gamma2.

Variables:

  • u_range (tuple) – The interpolation range of u parameter.

  • gamma2_range (tuple) – The interpolation range of \(\\gamma^2\) parameter.

  • raw_data (dict) – Dictionary containing the raw data.

evaluate(z, temperature, wavelength)

Returns the temperature-averaged free-free Gaunt factor for the supplied parameters.

Parameters:

  • z (double) – Species charge or effective plasma charge.

  • temperature (double) – Electron temperature in eV.

  • wavelength (double) – Spectral wavelength.

Returns:

free-free Gaunt factor

class cherab.core.atomic.gaunt.MaxwellianFreeFreeGauntFactor

Bases: InterpolatedFreeFreeGauntFactor

The Maxwellian-averaged free-free Gaunt factor interpolated over the data from Table A.1 in M.A. de Avillez and D. Breitschwerdt, “Temperature-averaged and total free-free Gaunt factors for κ and Maxwellian distributions of electrons”, 2015, Astron. & Astrophys. 580, A124.

The Born approximation is used outside the interpolation range.