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openmc_interface

OpenMC neutron source interface.

AllReactions = tokamak_neutron_source.reactions.Reactions | tokamak_neutron_source.reactions.AneutronicReactions module-attribute

Represent a PEP 604 union type

E.g. for int | str

EnergySpectrumMethod

Bases: enum.Enum

Energy spectrum calculation method.

Source code in tokamak_neutron_source/energy.py 
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class EnergySpectrumMethod(Enum):
    """Energy spectrum calculation method."""

    DATA = auto()
    BALLABIO_GAUSSIAN = auto()
    BALLABIO_M_GAUSSIAN = auto()
    AUTO = auto()

AUTO = <EnergySpectrumMethod.AUTO: 4> class-attribute

Energy spectrum calculation method.

BALLABIO_GAUSSIAN = <EnergySpectrumMethod.BALLABIO_GAUSSIAN: 2> class-attribute

Energy spectrum calculation method.

BALLABIO_M_GAUSSIAN = <EnergySpectrumMethod.BALLABIO_M_GAUSSIAN: 3> class-attribute

Energy spectrum calculation method.

DATA = <EnergySpectrumMethod.DATA: 1> class-attribute

Energy spectrum calculation method.

QuietTTSpectrumWarnings

Bases: tokamak_neutron_source.tools.WarningFilter

Filter away all duplicate warnings from the energy and energy_data module.

Source code in tokamak_neutron_source/tools.py 
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class QuietTTSpectrumWarnings(WarningFilter):
    """Filter away all duplicate warnings from the energy and energy_data module."""

    def __init__(self):
        super().__init__(
            "tokamak_neutron_source.energy", "tokamak_neutron_source.energy_data"
        )

Reactions

Bases: tokamak_neutron_source.reactions.ReactionEnumMixin, enum.Enum

Neutronic reaction channels.

Source code in tokamak_neutron_source/reactions.py 
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class Reactions(ReactionEnumMixin, Enum):
    """Neutronic reaction channels."""

    D_T = ReactionData(
        label="D + T → ⁴He + n",
        total_energy=E_DT_FUSION,
        num_neutrons=1,
        cross_section=DT_XS,
        bosch_hale_coefficients=BOSCH_HALE_DT_4HEN,
        ballabio_spectrum=BALLABIO_DT_NEUTRON,
    )
    D_D = ReactionData(
        label="D + D → ³He + n",
        total_energy=E_DD_HE3N_FUSION,
        num_neutrons=1,
        cross_section=DD_HE3N_XS,
        bosch_hale_coefficients=BOSCH_HALE_DD_3HEN,
        ballabio_spectrum=BALLABIO_DD_NEUTRON,
    )
    T_T = ReactionData(
        label="T + T → ⁴He + 2n",
        total_energy=E_TT_FUSION,
        num_neutrons=2,
        cross_section=TT_XS,
        bosch_hale_coefficients=None,
        ballabio_spectrum=None,
    )

D_D = <Reactions.D_D: ReactionData(label='D + D → ³He + n', total_energy=5.237367559215132e-13, num_neutrons=1, cross_section=<tokamak_neutron_source.reactivity_data.ReactionCrossSection object at 0x7fb53dd00150>, bosch_hale_coefficients=BoschHaleCoefficients(name='D + D --> 3He + n', t_min=0.2, t_max=100.0, bg=31.397, mrc2=937814.0, c=array([ 5.43360e-12, 5.85778e-03, 7.68222e-03, 0.00000e+00,-2.96400e-06, 0.00000e+00, 0.00000e+00])), ballabio_spectrum=BallabioEnergySpectrum(energy_0=2449.5, omega_0=82.542, energy_shift_coeffs=BallabioCoefficients(a1=4.69515, a2=-0.040729, a3=0.47, a4=0.81844), width_correction_coeffs=BallabioCoefficients(a1=0.0017013, a2=0.16888, a3=0.49, a4=0.0007946)))> class-attribute

Neutronic reaction channels.

D_T = <Reactions.D_T: ReactionData(label='D + T → ⁴He + n', total_energy=2.8183035155819573e-12, num_neutrons=1, cross_section=<tokamak_neutron_source.reactivity_data.ReactionCrossSection object at 0x7fb504da0250>, bosch_hale_coefficients=BoschHaleCoefficients(name='D + T --> 4He + n', t_min=0.2, t_max=100.0, bg=34.3827, mrc2=1124656.0, c=array([ 1.17302e-09, 1.51361e-02, 7.51886e-02, 4.60643e-03,1.35000e-02, -1.06750e-04, 1.36600e-05])), ballabio_spectrum=BallabioEnergySpectrum(energy_0=14021.0, omega_0=177.259, energy_shift_coeffs=BallabioCoefficients(a1=5.30509, a2=0.0024736, a3=1.84, a4=1.3818), width_correction_coeffs=BallabioCoefficients(a1=0.00051068, a2=0.0076223, a3=1.78, a4=8.7691e-05)))> class-attribute

Neutronic reaction channels.

T_T = <Reactions.T_T: ReactionData(label='T + T → ⁴He + 2n', total_energy=1.8157845541890245e-12, num_neutrons=2, cross_section=<tokamak_neutron_source.reactivity_data.ReactionCrossSection object at 0x7fb504d603d0>, bosch_hale_coefficients=None, ballabio_spectrum=None)> class-attribute

Neutronic reaction channels.

get_neutron_energy_spectrum(reaction, temp_kev, method)

Get a native OpenMC neutron energy spectrum.

Parameters:

Name Type Description Default
reaction Reactions

The neutronic reaction for which to retrieve the neutron spectrum

 required
temp_kev float

The ion temperature of the reactants

 required
method EnergySpectrumMethod

Which method to use when calculating the energy spectrum

 required

Returns:

Type Description
Tabular | Discrete

OpenMC tabular neutron energy distribution for the given reaction.
Notes

Log-linear interpolation is used within OpenMC.

Source code in tokamak_neutron_source/openmc_interface.py 
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def get_neutron_energy_spectrum(
    reaction: Reactions, temp_kev: float, method: EnergySpectrumMethod
) -> Tabular | Discrete:
    """
    Get a native OpenMC neutron energy spectrum.

    Parameters
    ----------
    reaction:
        The neutronic reaction for which to retrieve the neutron spectrum
    temp_kev: float
        The ion temperature of the reactants
    method:
        Which method to use when calculating the energy spectrum

    Returns
    -------
    :
        OpenMC tabular neutron energy distribution for the given reaction.

    Notes
    -----
    Log-linear interpolation is used within OpenMC.
    """
    if (
        method is EnergySpectrumMethod.BALLABIO_GAUSSIAN
        and reaction.ballabio_spectrum is not None
    ):
        mean = reaction.ballabio_spectrum.mean_energy(temp_kev)
        std = reaction.ballabio_spectrum.std_deviation(temp_kev)
        return Normal(raw_uc(mean, "keV", "eV"), raw_uc(std, "keV", "eV"))
    energy, probability = energy_spectrum(temp_kev, reaction, method)
    energy_ev = raw_uc(energy, "keV", "eV")
    # Log-linear interpolation is not supported in OpenMC at present
    # see: https://github.com/openmc-dev/openmc/issues/2409
    return Tabular(energy_ev, probability, interpolation="linear-linear")

make_openmc_ring_source(r, z, half_cell_length, energy_distribution, strength)

Make a single OpenMC ring source with a square cross-section.

Parameters:

Name Type Description Default
r float

Radial position of the centroid of the 3-D ring [m]

 required
z float

Vertical position of the centroid of the 3-D ring [m]

 required
half_cell_length float

Half the square cell length [m]

 required
energy_distribution Univariate

Neutron energy distribution

 required
strength float

Strength of the source [number of neutrons]

 required

Returns:

Type Description
IndependentSource

An OpenMC IndependentSource object, or None if strength is zero.
Notes

The z values within the square cell are uniform, and the r values vary linearly with increasing radius.

Source code in tokamak_neutron_source/openmc_interface.py 
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def make_openmc_ring_source(
    r: float,
    z: float,
    half_cell_length: float,
    energy_distribution: Univariate,
    strength: float,
) -> IndependentSource:
    """
    Make a single OpenMC ring source with a square cross-section.

    Parameters
    ----------
    r:
        Radial position of the centroid of the  3-D ring [m]
    z:
        Vertical position of the centroid of the 3-D ring [m]
    half_cell_length:
        Half the square cell length [m]
    energy_distribution:
        Neutron energy distribution
    strength:
        Strength of the source [number of neutrons]

    Returns
    -------
    :
        An OpenMC IndependentSource object, or None if strength is zero.

    Notes
    -----
    The z values within the square cell are uniform, and the r values vary
    linearly with increasing radius.
    """
    if strength > 0:
        r_in, r_out = r - half_cell_length, r + half_cell_length
        z_down, z_up = z - half_cell_length, z + half_cell_length
        r_lim_cm = raw_uc([r_in, r_out], "m", "cm")
        z_lim_cm = raw_uc([z_down, z_up], "m", "cm")
        r_lim_prob = np.array(r_lim_cm) / sum(r_lim_cm)
        return IndependentSource(
            energy=energy_distribution,
            space=CylindricalIndependent(
                r=Tabular(r_lim_cm, r_lim_prob, interpolation="linear-linear"),
                phi=Uniform(0, 2 * np.pi),
                z=Uniform(*z_lim_cm),
                origin=(0.0, 0.0, 0.0),
            ),
            angle=Isotropic(),
            strength=strength,
        )
    return None

make_openmc_full_combined_source(r, z, cell_side_length, temperature, strength, source_rate, energy_spectrum_method=<EnergySpectrumMethod.AUTO: 4>)

Make an OpenMC source combining multiple reactions across the whole plasma.

Parameters:

Name Type Description Default
r ndarray[tuple[Any, ...], dtype[~_ScalarT]]

Radial positions of the rings [m]

 required
z ndarray[tuple[Any, ...], dtype[~_ScalarT]]

Vertical positions of the rings [m]

 required
cell_side_length float

Radial and vertical spacings of the rings [m]

 required
temperature ndarray[tuple[Any, ...], dtype[~_ScalarT]]

Ion temperatures at the rings [keV]

 required
strength dict[Reactions | AneutronicReactions, ndarray[tuple[Any, ...], dtype[~_ScalarT]]]

Dictionary of strengths for each reaction at the rings [neutrons]

 required
source_rate float

Total source rate [neutrons/s]

 required
energy_spectrum_method EnergySpectrumMethod

Which method to use when calculating neutron spectra

 <EnergySpectrumMethod.AUTO: 4>

Returns:

Type Description
IndependentSource

A list of OpenMC IndependentSource objects, one per ring.
Source code in tokamak_neutron_source/openmc_interface.py 
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def make_openmc_full_combined_source(  # noqa: PLR0913, PLR0917
    r: npt.NDArray,
    z: npt.NDArray,
    cell_side_length: float,
    temperature: npt.NDArray,
    strength: dict[AllReactions, npt.NDArray],
    source_rate: float,
    energy_spectrum_method: EnergySpectrumMethod = EnergySpectrumMethod.AUTO,
) -> IndependentSource:
    """
    Make an OpenMC source combining multiple reactions across the whole plasma.

    Parameters
    ----------
    r:
        Radial positions of the rings [m]
    z:
        Vertical positions of the rings [m]
    cell_side_length:
        Radial and vertical spacings of the rings [m]
    temperature:
        Ion temperatures at the rings [keV]
    strength:
        Dictionary of strengths for each reaction at the rings [neutrons]
    source_rate:
        Total source rate [neutrons/s]
    energy_spectrum_method:
        Which method to use when calculating neutron spectra

    Returns
    -------
    :
        A list of OpenMC IndependentSource objects, one per ring.
    """
    sources = []
    # Neutronic reaction channels only
    # We multiply the T-T channel by 2 because it is 2n
    n_strength = {
        reaction: rate * reaction.num_neutrons
        for reaction, rate in strength.items()
        if isinstance(reaction, Reactions)
    }

    l_2 = cell_side_length / 2
    with QuietTTSpectrumWarnings():
        for i, (ri, zi, ti) in enumerate(zip(r, z, temperature, strict=False)):
            distributions = []
            weights = []

            for reaction, s in n_strength.items():
                if s[i] > 0.0:
                    distributions.append(
                        get_neutron_energy_spectrum(reaction, ti, energy_spectrum_method)
                    )
                    weights.append(s[i])

            local_strength = sum(weights)

            distribution = Mixture(np.array(weights) / local_strength, distributions)

            source = make_openmc_ring_source(
                ri,
                zi,
                l_2,
                distribution,
                local_strength / source_rate,
            )
            if source is not None:
                sources.append(source)

    return sources

energy_spectrum(temp_kev, reaction, method=<EnergySpectrumMethod.BALLABIO_M_GAUSSIAN: 3>)

Calculate the tabulated energy spectrum of a reaction at a given ion temperature.

Parameters:

Name Type Description Default
temp_kev float

Ion temperature

 required
reaction Reactions

Neutronic fusion reaction

 required
method EnergySpectrumMethod

Method to use to calculate the energy spectrum

 <EnergySpectrumMethod.BALLABIO_M_GAUSSIAN: 3>

Returns:

Name Type Description
energies ndarray[tuple[Any, ...], dtype[~_ScalarT]]

The energy bins of the probability distribution function
pdf ndarray[tuple[Any, ...], dtype[~_ScalarT]]

The PDF values
Source code in tokamak_neutron_source/energy.py 
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def energy_spectrum(
    temp_kev: float,
    reaction: Reactions,
    method: EnergySpectrumMethod = EnergySpectrumMethod.BALLABIO_M_GAUSSIAN,
) -> tuple[npt.NDArray, npt.NDArray]:
    """
    Calculate the tabulated energy spectrum of a reaction at a given ion temperature.

    Parameters
    ----------
    temp_kev:
        Ion temperature
    reaction:
        Neutronic fusion reaction
    method:
        Method to use to calculate the energy spectrum

    Returns
    -------
    energies:
        The energy bins of the probability distribution function
    pdf:
        The PDF values
    """
    match method:
        case (
            EnergySpectrumMethod.BALLABIO_GAUSSIAN
            | EnergySpectrumMethod.BALLABIO_M_GAUSSIAN
        ):
            if reaction.ballabio_spectrum is not None:
                return _ballabio_spectrum(reaction.ballabio_spectrum, temp_kev, method)

            logger.warning(
                f"There is no Ballabio parameterisation for reaction {reaction.name}, "
                "returning energy spectrum calculated by data.",
                stacklevel=5,
            )
            return _data_spectrum(reaction, temp_kev)

        case EnergySpectrumMethod.DATA:
            return _data_spectrum(reaction, temp_kev)
        case EnergySpectrumMethod.AUTO:
            match reaction:
                case Reactions.D_D | Reactions.D_T:
                    return energy_spectrum(
                        temp_kev, reaction, EnergySpectrumMethod.BALLABIO_M_GAUSSIAN
                    )
                case Reactions.T_T:
                    return energy_spectrum(temp_kev, reaction, EnergySpectrumMethod.DATA)

raw_uc(value, unit_from, unit_to)

Raw unit converter Converts a value from one unit to another

Parameters:

Name Type Description Default
value ValueLikeT

value to convert

 required
unit_from str | Unit

unit to convert from

 required
unit_to str | Unit

unit to convert to

 required

Returns:

Type Description
ValueLikeT

converted value
Source code in tokamak_neutron_source/constants.py 
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def raw_uc(
    value: ValueLikeT,
    unit_from: str | ureg.Unit,
    unit_to: str | ureg.Unit,
) -> ValueLikeT:
    """
    Raw unit converter
    Converts a value from one unit to another

    Parameters
    ----------
    value:
        value to convert
    unit_from:
        unit to convert from
    unit_to:
        unit to convert to

    Returns
    -------
    :
        converted value
    """
    try:
        return (
            ureg.Quantity(value, ureg.Unit(unit_from)).to(ureg.Unit(unit_to)).magnitude
        )
    except ValueError:
        # Catch scales on units eg the ridculousness of this unit: 10^19/m^3
        unit_from_q = ureg.Quantity(unit_from)
        unit_to_q = ureg.Quantity(unit_to)
        return (
            ureg.Quantity(value * unit_from_q).to(unit_to_q.units).magnitude
            / unit_to_q.magnitude
        )