Yet Another NeoClassical Code.

yancc solves the drift kinetic equation to compute neoclassical flows and transport fluxes in toroidal geometry (both tokamaks and stellarators).

Installation

yancc is a pure-Python package built on JAX and requires Python 3.10 or newer.

From PyPI:

pip install yancc

From source (for development):

git clone https://github.com/f0uriest/yancc.git
cd yancc
pip install -e ".[dev]"

JAX provides separate wheels for CPU and GPU backends; see the JAX install guide to pick the appropriate one for your hardware.

Example: Solving the Drift Kinetic Equation

A minimal end-to-end DKE solve for a single hydrogen species:

from yancc import (
    Field,
    Hydrogen,
    LocalMaxwellian,
    MaxwellSpeedGrid,
    UniformPitchAngleGrid,
    solve_dke,
)

# Field and grids.
rho = 0.5
nt, nz, na, nx = 15, 31, 61, 6
field = Field.from_vmec("wout_NCSX.nc", rho, nt, nz)
pitchgrid = UniformPitchAngleGrid(na)
speedgrid = MaxwellSpeedGrid(nx)

# Single hydrogen species. Density and temperature gradients are with
# respect to rho = sqrt(normalized toroidal flux), so multiply physical
# gradients by the minor radius.
species = [
    LocalMaxwellian(
        Hydrogen,
        temperature=0.8e3,                        # eV
        density=1.5e20,                           # 1/m^3
        dTdrho=-2.0e3 * field.a_minor,
        dndrho=-0.4e20 * field.a_minor,
    )
]

# Radial electric field, in Volts. Erho = -dPhi/drho.
Er_kV_per_m = 0.5
Erho = Er_kV_per_m * field.a_minor * 1000

sol, info = solve_dke(
    field,
    pitchgrid,
    speedgrid,
    species,
    Erho=Erho,
    verbose=2,
    rtol=1e-5,
)

print("<Gamma>  =", sol.get("<particle_flux>"))   # particles/(m^2 s)
print("<Q>      =", sol.get("<heat_flux>"))       # J/(m^2 s)
print("<V||B>   =", sol.get("<V||B>"))            # T*m/s
print("<J||B>   =", sol.get("<J||B>"))            # T*A/m^2

See the documentation for the monoenergetic solver, multi-species runs, the full list of output variables, and the API reference.