Is a tool for creating axially symmetric CSG geometry. By revolving polygons around an axis, we get toroids -- a torus-like surface, which is a composite of conical, planar and cylindrical surfaces.
Below is an example of an ITER-like simplified model generated with PolygonTorus. This is a fully CSG model consiting of only 9 cells and 309 surfaces.
Currently it generates CSG geometry for openMC and MCNP. When generating MCNP geometry the tool can be used by itself, whereas when generating openMC geometry, openMC is used for the construction of surfaces and regions.
The tool is in its early stages:
- There are two separate modules for openMC and MCNP inputs.
- Code is not well documented.
- For MCNP: The tool generates only regions. The generation of cells is made easier with the
split_into_lines()function, but is still cumbersome.
For a theoretical explanation see polygontorus_presentation.pdf. For examples see examples folder.
Offset(): Because of its robust definition of geometry this tool can be used for arbitrarily thin layers. When generating thick layers inside the shells (negative offset), caution should be used since vertices may get deleted.
- Generation of a Polygon with many vertices in MCNP. This can result in a region definition that is too big for MCNP (MCNP 5.16 was tested).
- The
split_into_lines()function is buggy at times. - Supports only convex polygons. Region splitting should be implemented (also to ensure cell definitions are more simple - see 1st limitation).
- Performance assessment of polygon torus vs. toroidal surfaces
- Better MCNP workflow
Recently, the creation of an axially symmetric CSG geometry from a revolved polygon defined with vertices has been achieved by multiple parties, independently:
- OceanNuclear for bluemira
- openmc.model.Polygon. The openmc feature nicely handles non-convex polygons.
Basics of the PolygonTorus tool and how it was used to make the ITER Neutron Calibration Simplified Model (NCSM) is presented in:
- M. Fortuna, B. Coriton, A. Čufar, S. Di Sarra, G. Mariano and L. Snoj, A Simplified Monte Carlo Model of the ITER Tokamak for Neutron Calibration Calculations. Proceedings of the International Conference Nuclear Energy for New Europe, Portorož, Slovenia, September 7–10, 2026.
The geometry of the ITER Neutron Calibration Simplified Model (NCSM) which is available in the examples folder was made from publicly available data. The NCSM model was used in:
- G. Mariano et al. Calibration strategy and uncertainty analysis of the iter neutron activation system for deuterium–deuterium plasma operation. Nuclear Fusion, 66(8):086015, jul 2026.
- M. Fortuna et al. Nuclear Data Uncertainty Propagation to Neutron Diagnostics. 15th-ITER Neutronics meeting and Fusion Neutronics Workshop, April 9, 2024.
- Q. Potiron et al. Optimisation of ITER In-Vessel Neutron Calibration. 34-th Symposium on Fusion Technology, Aix-en-Provence, France, September 20-25, 2026.
- M. Fortuna et al. Estimation of Uncertainty in the Line-of-Sight of the ITER In-Port Radial Neutron Camera due to Fission Chamber Isotopic Composition. 34-th Symposium on Fusion Technology, Aix-en-Provence, France, September 20-25, 2026.