Symplectic Integration Methods for Particle Loss Estimation
SIMPLE traces guiding-centre orbits of energetic particles, by default 3.5 MeV fusion alphas, in three-dimensional magnetic fields and reports when and where they leave the plasma. It integrates in canonical coordinates with symplectic schemes and classifies orbits as regular or chaotic, which makes alpha-loss estimates cheap enough for stellarator optimisation loops.
- Field input: VMEC equilibria, Boozer chartmaps (GVEC, booz_xform), coil files, SPECTRE multi-volume equilibria.
- Physics options: collisions with a background plasma, fusion-weighted alpha births, STL wall intersection, orbit classification, full orbits.
- OpenMP over particles, an optional native CUDA backend, and the Python
package
pysimple.
With GNU Fortran, CMake ≥ 3.22, Ninja, NetCDF-C/Fortran and BLAS/LAPACK installed:
git clone https://github.com/itpplasma/SIMPLE.git && cd SIMPLE
make
mkdir -p run && cp examples/simple.in run/
curl -L -o run/wout.nc https://github.com/hiddenSymmetries/simsopt/raw/master/tests/test_files/wout_LandremanPaul2021_QA_reactorScale_lowres_reference.nc
(cd run && ../build/simple.x simple.in && tail -1 confined_fraction.dat)This traces 128 alphas for 10 ms in a public quasi-axisymmetric reactor
equilibrium. The quick start
explains the output; the installation guide
covers packages per platform, CMake options and pysimple.
Manual: https://itpplasma.github.io/SIMPLE/latest/. Contributing: CONTRIBUTING.md. Mirror with release tags: https://gitlab.eufus.psnc.pl/itpplasma/simple.
Cite the methods your study uses:
- Symplectic guiding-centre integration: Albert, Kasilov, Kernbichler, J. Comput. Phys. 403, 109065 (2020), doi:10.1016/j.jcp.2019.109065.
- Accelerated alpha-loss computation: Albert, Kasilov, Kernbichler, J. Plasma Phys. 86, 815860201 (2020), doi:10.1017/S0022377820000203.
- Orbit classification: Albert et al., J. Plasma Phys. 89, 955890301 (2023), doi:10.1017/S0022377823000351.
- Wall heat loads: Albert et al., Nucl. Mater. Energy 48, 102200 (2026), doi:10.1016/j.nme.2026.102200.
Full references: publications page and CITATION.cff.
MIT. The FIRM3D-compatible tracing path has separate provenance and license information.