singularity-opac

Performance Portable Opacity and Emissivity library for simulation codes

API

singularity-opac provides a uniform API for all opacity models, in two forms: frequency-dependent, and frequency-averaged (Plank or Rosseland means), and separately for absorption and scattering opacities.

For frequency-dependent absorption opacities, the following functions are provided (here, $\sigma$ is the frequency- and angle-dependent cross section in units of ${\rm cm}^2$):

Function	Expression	Description	Units
AbsorptionCoefficient	$n \sigma$	Absorption coefficient	${\rm cm}^{-1}$
AngleAveragedAbsorptionCoefficient	$\frac{1}{4 \pi}\int n \sigma d\Omega$	Absorption coefficient averaged over solid angle	${\rm cm}^{-1}$
EmissivityPerNuOmega	$j_{\nu} = \frac{dE}{d^3x dt d\Omega d\nu}$	Frequency- and angle-dependent emissivity	${\rm erg}{\rm cm}^{-3}{\rm s}^{-1}{\rm Hz}^{-1}{\rm Sr}^{-1}$
EmissivityPerNu	$\int j_{\nu} d\Omega$	Frequency-dependent emissivity	${\rm erg}{\rm cm}^{-3}{\rm s}^{-1}{\rm Hz}^{-1}$
Emissivity	$\int j_{\nu} d\nu d\Omega$	Total emissivity	${\rm erg}{\rm cm}^{-3}{\rm s}^{-1}$
NumberEmissivity	$\int \frac{1}{h \nu} j_{\nu} d\Omega d\nu$	Total number emissivity	${\rm cm}^{-3}{\rm s}^{-1}$
ThermalDistributionOfTNu	$B_{\nu} = \frac{dE}{dA dt d\Omega d\nu}$	Specific intensity of thermal distribution	${\rm erg}{\rm cm}^{-2}{\rm s}^{-1}{\rm Sr}^{-1}{\rm Hz}^{-1}$
DThermalDistributionOfTNuDT	$dB_{\nu}/dT$	Temperature derivative of specific intensity of thermal distribution	${\rm erg}{\rm cm}^{-2}{\rm s}^{-1}{\rm Sr}^{-1}{\rm Hz}^{-1}{\rm K}^{-1}$
ThermalDistributionOfT	$B = \int B_{\nu} d\Omega d\nu$	Frequency- and angle-integrated intensity of thermal distribution	${\rm erg}{\rm cm}^{-2}{\rm s}^{-1}$
ThermalNumberDistributionOfT	$B = \int \frac{1}{h \nu} B_{\nu} d\Omega d\nu$	Frequency- and angle-integrated intensity of thermal distribution	${\rm erg}{\rm cm}^{-2}{\rm s}^{-1}$
EnergyDensityFromTemperature	$E_{\rm R}$	Radiation energy density	${\rm erg}{\rm cm}^{-3}$
TemperatureFromEnergyDensity	$T_{\rm R}$	Radiation temperature	${\rm K}$
NumberDensityFromTemperature	$n_{\rm R}$	Radiation number density	${\rm cm}^{-3}$

with the following function signatures:

AbsorptionCoefficient(density, temperature, frequency)
AngleAveragedAbsorptionCoefficient(density, temperature, frequency)
EmissivityPerNuOmega(density, temperature, frequency)
EmissivityPerNu(density, temperature, frequency)
Emissivity(density, temperature)
NumberEmissivity(density, temperature)
ThermalDistributionOfTNu(temperature, frequency)
DThermalDistribtuionOfTNuDT(temperature, frequency)
ThermalDistributionOfT(temperature)
ThermalNumberDistributionOfT(temperature)
EnergyDensityFromTemperature(temperature)
TemperatureFromEnergyDensity(radiation energy density)
NumberDensityFromTemperature(temperature)

For mean absorption opacities, the following functions are provided:

Function	Expression	Description	Units
PlankMeanAbsorptionCoefficient	$n \sigma$	Absorption coefficient	${\rm cm}^{-1}$
RosselandMeanAbsorptionCoefficient	$n \sigma$	Absorption coefficient	${\rm cm}^{-1}$
AbsorptionCoefficient	$n \sigma$	Absorption coefficient	${\rm cm}^{-1}$
Emissivity	$\int j_{\nu} d\nu d\Omega$	Total emissivity	${\rm erg}{\rm cm}^{-3}{\rm s}^{-1}$

with the following function signatures:

PlanckMeanAbsorptionCoefficient(density, temperature)
RosselandMeanAbsorptionCoefficient(density, temperature)
AbsorptionCoefficient(density, temperature, gmode [Planck, Rosseland])
Emissivity(density, temperature)

For frequency-dependent scattering opacities, the following functions are provided

Function	Expression	Description	Units
TotalCrossSection	$\sigma$	Scattering cross section	${\rm cm}^{2}$
DifferentialCrossSection	$d\sigma / d \Omega $	Differential scattering cross section	${\rm cm}^{2}{\rm Sr}^{-1}$
TotalScatteringCoefficient	$n \sigma $	Scattering coefficient	${\rm cm}^{-1}$

with the following function signatures:

TotalCrossSection(density, temperature, frequency)
DifferentialCrossSection(density, temperature, frequency, cos(theta))
TotalScatteringCoefficient(density, temperature, frequency)

For mean scattering opacities, the following functions are provided:

Function	Expression	Description	Units
PlanckMeanScatteringCoefficient	$n \sigma$	Planck mean scattering coefficient	${\rm cm}^{-1}$
RosselandMeanScatteringCoefficient	$n \sigma$	Rosseland mean scattering coefficient	${\rm cm}^{-1}$

with the following function signatures:

PlanckMeanScatteringCoefficient(density, temperature)
RosselandMeanScatteringCoefficient(density, temperature)

Note that the thermal radiation energy density u = 1/c ThermalDistributionOfT and the thermal radiation number density n = 1/c ThermalNumberDistributionOfT.

Opacity variant constructors are specific to the opacity model being requested; consult the source code for individual opacities.

Internally singularity-opac always uses CGS units, as in the above table. However, arbitrary units are supported through the units modifier, which accepts function argument inputs in the arbitrary unit system, and returns the result from the function in those same arbitrary units. For example, a gray absorption opacity in non-cgs units specified by time_unit, mass_unit, length_unit, and temp_unit conversion factors from code to CGS units (e.g. mass_cgs = mass_unit * mass_code) is created as

photons::Opacity noncgs_opacity = photons::NonCGSUnits<photons::Gray>(
      photons::Gray(kappa), time_unit, mass_unit, length_unit, temp_unit);

Note that neutrino opacity functions also include electron fraction and RadiationType species arguments.

Frequency-dependent emissition and absorption functions do not currently support angle dependence.

A struct of runtime physical constants is provided for optional consistency with internal operations by the GetRuntimePhysicalConstants() method.

To Build

At its most basic:

git clone --recursive git@github.com:lanl/singularity-opac.git
cd singularity-opac
mkdir bin
cd bin
cmake ..
make

To Make tests

Then, in the singularity-opac root directory:

mkdir -p bin
cd bin
cmake -DSINGULARITY_BUILD_TESTS=ON ..
make -j
make test

Build Options

A number of options are avaialable for compiling:

Option	Default	Comment
SINGULARITY_BUILD_TESTS	OFF	Build test infrastructure.
SINGULARITY_USE_HDF5	ON	Enables HDF5. Required for Spiner opacities.
SINGULARITY_KOKKOS_IN_TREE	OFF	Force cmake to use Kokkos source included in tree.

Loading ASCII Data

Currently, the MeanOpacity class, defined in singularity-opac/photons/mean_opacity_photons.hpp, supports loading grey Rosseland and Planck opacity data in an ASCII format. An example of this format is provided by singularity-opac/photons/example_ascii/kap_plaw.txt. The 1st row of the header has the number of density points, NRho, then the number of temperature points, NT. The 2nd (3rd) row of the header has min and max density (temperature) bounds. These bounds are inclusive, so the opacity data in the file should have evaluations at these min and max values. The rest of the ASCII file is a two-column table, where the 1st (2nd) column is Rosseland (Planck) opacity. The number of rows in each column is NRhoxNT, where density is the slow index and temperature is the fast index (thus the row index = temperature index

• NT x (density index), indexing from 0). Each opacity is assumed to be evaluated on log-spaced density and temperature grids, where these grids are defined by NRho, NT, and the (again inclusive) min and max bounds the header.

Copyright

© 2021. Triad National Security, LLC. All rights reserved. This program was produced under U.S. Government contract 89233218CNA000001 for Los Alamos National Laboratory (LANL), which is operated by Triad National Security, LLC for the U.S. Department of Energy/National Nuclear Security Administration. All rights in the program are reserved by Triad National Security, LLC, and the U.S. Department of Energy/National Nuclear Security Administration. The Government is granted for itself and others acting on its behalf a nonexclusive, paid-up, irrevocable worldwide license in this material to reproduce, prepare derivative works, distribute copies to the public, perform publicly and display publicly, and to permit others to do so.