Flan

Fully kinetic Monte Carlo to follow trace amount of impurities in a turbulent plasma.

Flan is named after my dog, Flannery. It does not stand for anything.

Typical usage is to track a trace amount of impurities in a turbulent background generated by Gkeyll. Flan follows impurities in a plasma in a fully kinetic, Monte Carlo sense and is built on first-principles.

• The particles are tracked according to Lorentz force using the energy conserving Boris time stepping algorithm: $$\vec{F}=m(\vec{E} + \vec{v} \times \vec{B})$$
• Particle ionization and recombination is tracked via coupling to ADAS
• The collision model is based on the publication: Nanbu, K. Theory of cumulative small-angle collisions in plasmas. Phys. Rev. E 55, 4642–4652 (1997). This is a fully general collision scheme for Monte Carlo applications valid in all plasma regimes (with the only approximation being the plasma is in thermal equlibrium when calculating the Coulomb logarithm, likely a relatively negligible effect).

A publication detailing Flan is anticipated in 2025.

Documentation

Link to the ReadTheDocs

Upcoming Changes

• Restructure impurity transport routines to use SoA for efficient GPU implementation (ongoing)
• Couple to CGYRO and/or SOLEDGE3X (starting late 2026)
• Incorporate MPI to spread computation across multiple nodes Merged to main 6/3/26
• Add time profiling Merged to main 7/31/25
• Upgrade to Nanbu collision model Merged to main 7/23/25
• Expand code to non-Cartesian geometries (e.g., tokamak coordinates) Merged to main 5/30/25

FLAN is dual-licensed under the GNU General Public License v3.0 (GPLv3) and a commercial license.

• The GPLv3 license applies to all open-source use.
• A commercial license is available for organizations that wish to use FLAN in proprietary software, avoid GPL obligations, or obtain commercial support.

For commercial licensing inquiries, please contact: zamperinis@fusion.gat.com.