Input Deck Reference

Auto-generated from schema.lua. Each table below documents one section of the config table.

config.basis

Key	Type	Default	Required	Description
nnodes	double	—	No	Number of DG nodes per cell.

config.bc

fluid

Key	Type	Default	Required	Description
bc_i	string	—	No	Inner fluid boundary condition. Options: ‘reflecting’, ‘outflow’, ‘surface’, ‘periodic’.
bc_o	string	—	No	Outer fluid boundary condition. Options: ‘reflecting’, ‘outflow’, ‘surface’, ‘periodic’.
surface_pressure_i	number	—	No	Prescribed pressure at an inner surface boundary. Defaults to zero.
surface_pressure_o	number	—	No	Prescribed pressure at an outer surface boundary. Defaults to zero.

radiation

Key	Type	Default	Required	Description
bc_i	string	—	No	Inner radiation boundary condition. Options: ‘reflecting’, ‘interior’, ‘free_streaming’, ‘marshak’, ‘periodic’. ‘interior’ uses the interior-state physical flux, analogous to fluid outflow but not a no-incoming-characteristics condition.
bc_o	string	—	No	Outer radiation boundary condition. Options: ‘reflecting’, ‘interior’, ‘free_streaming’, ‘periodic’. ‘interior’ uses the interior-state physical flux, analogous to fluid outflow but not a no-incoming-characteristics condition.
marshak_incoming_energy_i	number	—	No	Incoming volumetric radiation energy for an inner Marshak boundary.

config.composition

Key	Type	Default	Required	Description
ncomps	int	—	No	Number of composition species.

config.diagnostics

optical_depth

Key	Type	Default	Required	Description
enabled	bool	false	No	Enable Rosseland optical depth output integrated inward from the outer boundary.

photosphere

Key	Type	Default	Required	Description
enabled	bool	false	No	Enable photosphere history tracking from the optical-depth profile.
tau	double	0.6666666666666666	No	Optical-depth threshold used by the photosphere tracker. Must be > 0.

shock

Key	Type	Default	Required	Description
enabled	bool	false	No	Enable shock history tracking using the strongest velocity compression.

config.engine

thermal

Key	Type	Default	Required	Description
enabled	bool	—	No	Enable thermal energy injection engine.
energy	double	—	No	Total injected energy in erg.
mend	double	—	No	Mass coordinate of injection upper boundary in Msun. Must be > 0.
mode	string	—	No	Injection mode. Options: ‘direct’, ‘asymptotic’.
operator_split	bool	false	No	Apply engine as operator-split source.
tend	double	—	No	End time for energy injection. Must be > 0.

config.eos

Key	Type	Default	Required	Description
gamma	double	1.4	No	Adiabatic index. Default: 1.4.
k	double	—	No	Polytropic constant K. Required for polytropic EOS.
n	double	—	No	Polytropic index n. Required for polytropic EOS.
type	string	—	No	Equation of state type. Options:. ‘ideal’, ‘paczynski’, ‘marshak’, ‘polytropic’.

config.fluid

limiter

Key	Type	Default	Required	Description
b_tvd	double	1.0	No	TVD parameter b. Used with minmod limiter.
characteristic	bool	false	No	Enable characteristic limiting.
enabled	bool	true	No	Enable slope limiter for fluid.
gamma_i	double	—	No	WENO central weight. Required for WENO limiter.
gamma_l	double	—	No	WENO left weight. Inferred from gamma_i if omitted.
gamma_r	double	—	No	WENO right weight. Inferred from gamma_i if omitted.
m_tvb	double	0.0	No	TVB parameter M. Used with minmod limiter.
tci_opt	bool	false	No	Enable troubled-cell indicator.
tci_val	double	—	No	Troubled-cell indicator threshold.
type	string	minmod	No	Limiter type. Options: ‘minmod’, ‘moment’, ‘weno [experimental]’.
weno_r	double	2.0	No	WENO smoothness exponent. Must be > 0.

config.gravity

Key	Type	Default	Required	Description
gval	double	—	No	Acceleration [cm s^-2] for the constant gravity model. Must be > 0.
limiter_energy_correction	bool	false	No	Experimental. Return to the fluid the gravitational potential energy that the end-of-step limiter moves by relocating interior mesh nodes, as a uniform per-cell specific-energy shift clamped to the EOS internal-energy floor. Cancels the committed-state limiter mesh work exactly, but not the per-stage-limiting or temporal residuals, so some drift remains. Not robust in violent/cold-supersonic regimes; see the gravity docs.
model	string	—	No	Gravity model. Options: ‘constant’, ‘spherical’.
operator_split	bool	false	No	Apply gravity as an operator-split source. Uses a self-contained direct source (pointwise g and g*v) instead of the coupled weak form, giving up well-balancing and exact energy conservation. Incompatible with limiter_energy_correction.

config.heating

nickel

Key	Type	Default	Required	Description
enabled	bool	—	No	Enable Ni56 decay heating.
model	string	—	No	Nickel heating model. Options. ‘jeffery’ and ‘full_trapping’.
operator_split	bool	false	No	Apply nickel heating as operator-split source.

config.ionization

Key	Type	Default	Required	Description
fn_degeneracy	string	—	No	Path to degeneracy factors atomic data file.
fn_ionization	string	—	No	Path to ionization atomic data file.
ncomps	int	—	No	Number of species for Saha solver.
solver	string	linear	No	Saha solver mode. Options: ‘linear’, ‘log’.

config.mesh

Key	Type	Default	Required	Description
geometry	string	—	No	Domain geometry. Options: ‘planar’, ‘spherical’.
grid_type	string	—	No	Grid spacing type. Options: ‘uniform’, ‘logarithmic’.
nx	double	—	No	Number of grid cells. Must be > 0.
xl	double	—	No	Left boundary of the domain.
xr	double	—	No	Right boundary of the domain. Must be > xl.

config.opacity

Key	Type	Default	Required	Description
filename	string	—	No	Path to tabular opacity HDF5 file.
kP	double	—	No	Planck mean opacity (cm^2/g). Required for constant and powerlaw.
kP_offset	double	0.0	No	Planck opacity additive offset. Powerlaw only.
kR	double	—	No	Rosseland mean opacity (cm^2/g). Required for constant and powerlaw.
kR_offset	double	0.0	No	Rosseland opacity additive offset. Powerlaw only.
rho_exp	double	—	No	Density exponent for powerlaw opacity.
t_exp	double	—	No	Temperature exponent for powerlaw opacity.
type	string	—	No	Opacity model. Options: ‘tabular’, ‘constant’, ‘powerlaw’.

floors

Key	Type	Default	Required	Description
core_planck	double	0.24	No	Core Planck floor. Used with core_envelope model.
core_rosseland	double	0.24	No	Core Rosseland floor. Used with core_envelope model.
env_planck	double	0.01	No	Envelope Planck floor. Used with core_envelope model.
env_rosseland	double	0.01	No	Envelope Rosseland floor. Used with core_envelope model.
planck	double	0.001	No	Planck floor value. Used with constant floor model.
rosseland	double	0.001	No	Rosseland floor value. Used with constant floor model.
type	string	core_envelope	No	Opacity floor model. Options: ‘core_envelope’, ‘constant’.

config.output

Key	Type	Default	Required	Description
basename	string		No	Optional prefix for HDF5 output filenames; prepended to the problem name.
dt_fixed	double	—	No	Fixed timestep override. Optional.
dt_growth_frac	double	1.05	No	Initial timestep growth factor. Must be > 1.
dt_hdf5	double	—	No	Time interval between HDF5 outputs. Default: t_end / 100.
dt_init	double	1.000000e-16	No	Initial timestep. Must be > 0.
ncycle_out	double	100	No	Number of cycles between stdout output.

history

Key	Type	Default	Required	Description
dt	double	—	No	Time interval between history writes. Default: dt_hdf5 / 10.
fn	string	athelas.hst	No	History output filename.

config.physics

Key	Type	Default	Required	Description
composition	bool	false	No	Enable multi-species composition.
engine	bool	false	No	Enable energy injection engine.
gravity	bool	false	No	Enable gravitational source terms.
heating	bool	false	No	Enable nuclear heating sources.
ionization	bool	false	No	Enable Saha ionization. Requires composition = true.
radiation	bool	false	No	Enable radiation transport.

config.problem

Key	Type	Default	Required	Description
cfl	double	—	No	CFL double for timestep control. Must be > 0.
name	string	—	No	Unique identifier for this simulation problem.
params	—	—	No	Problem-specific parameters. Validated by the problem generator.

config.radiation

Key	Type	Default	Required	Description
ap_coefficient	double	0.0	No	Coefficient C in the AP LLF damping factor 1 / (1 + C tau). C = 0 recovers standard LLF (no damping); C > 0 enables the optical-depth correction. Must be >= 0.
discretization	string	—	No	Spatial discretization of the transport term. Options: ‘implicit’ or ‘explicit’.

limiter

Key	Type	Default	Required	Description
b_tvd	double	1.0	No	TVD parameter b. Used with minmod limiter.
characteristic	bool	false	No	Enable characteristic limiting. Currently unsupported for radiation.
enabled	bool	true	No	Enable slope limiter for radiation.
gamma_i	double	—	No	WENO central weight. Required for WENO limiter.
gamma_l	double	—	No	WENO left weight. Inferred from gamma_i if omitted.
gamma_r	double	—	No	WENO right weight. Inferred from gamma_i if omitted.
m_tvb	double	0.0	No	TVB parameter M. Used with minmod limiter.
tci_opt	bool	false	No	Enable troubled-cell indicator.
tci_val	double	—	No	Troubled-cell indicator threshold.
type	string	minmod	No	Limiter type. Options: ‘minmod’, ‘moment’, ‘weno [experimental]’.
weno_r	double	2.0	No	WENO smoothness exponent. Must be > 0.

newton

Key	Type	Default	Required	Description
atol	double	0.0	No	Absolute residual tolerance for the implicit transport Newton iteration. Accepts the solve when the residual norm falls below this value regardless of relative reduction. 0 disables.
max_iter	int	10	No	Maximum Newton iterations for implicit transport solve.
tol	double	1.000000e-08	No	Convergence tolerance for implicit transport Newton iteration.

timestep

Key	Type	Default	Required	Description
energy_change_scale	double	1.000000e-10	No	Specific radiation energy scale used in the implicit transport relative-change timestep controller.
max_change_f	double	—	No	Maximum allowed absolute change in radiation reduced flux. Timestep control for implicit transport.
max_fractional_change_e	double	—	No	Maximum allowed fractional change in radiation energy. Timestep control for implicit transport.

config.time

Key	Type	Default	Required	Description
integrator	string	—	No	Time integration method. E.g. ‘IMEX_SSPRK11’, ‘IMEX_ARK32_ESDIRK’.
nlim	double	-1	No	Maximum number of cycles. -1 for unlimited.
t_end	double	—	No	End time of the simulation.