Equilibria
The poloidal flux from G-EQDSK files or the Solov’ev solution: the field, rho = sqrt(psi_n), flux shells with their volumes and aspect ratios, the boundary and the first wall as simgeometry polygons.
freeofcharge
Neutral beams in tokamak plasmas - where the beam is ionised, how much shines through onto the wall, and where the fast ions heat and drive current. Fast enough to sit inside an optimisation of the injector.
What is included
Section titled “What is included”Beams
Markers of fast atoms aimed with tangential_injection: Gaussian width and divergence, a halo, energy components.
Deposition
Every marker a straight line attenuated with Suzuki’s stopping cross sections (as in ASCOT5): birth profiles, sampled fast-ion births with their pitch, shine-through and where it hits the wall.
Slowing down
Classical (Stix) slowing down on the birth surface: heating of electrons and ions, fast-ion density and pressure, and the beam-driven current with electron shielding.
CPU, GPU, MPI
Arrays on the cunumpy backend (NumPy or CuPy); with MPI every rank traces its own markers and the profiles are summed once.
xarray output
Profiles convert to xarray datasets with units, ready for plasma-plots.
Where it fits
Section titled “Where it fits”freeofcharge is the last stage of the max-models chain of a neutral-beam injector, from the ion source to the plasma:
- Ion source and extraction - picnic (particle-in-cell) and wellbalanced (global and fluid models).
- Neutralizer - plasmacoll, the collisions of the
beam with the gas; freeofcharge’s markers are plasmacoll
ParticleArrays. - The plasma - freeofcharge: deposition, shine-through, heating and current drive.
The model is deliberately fast: straight lines and local slowing down, without orbit width, prompt losses, charge-exchange losses of fast ions or 3D effects. That is what a design scan over beam energy, aiming and density needs. For orbits and losses, the fast-ion births (positions, velocities and weights) can be the starting points of an orbit-following code.
Start here
Section titled “Start here”InstallationInstall the package and its max-models dependencies.
QuickstartDeposit a beam, slow down its fast ions, read off the current.
TutorialsFrom the equilibrium to an injector design scan, each step checked.
Full examplesA 1 MeV beam in an ITER-sized plasma, with a density scan.
API referenceGenerated from the docstrings.