COMPX^SM
Computational Modeling and Software Development

FIDASim-NT Neutral Transport

Description | Purpose | Algorithms | Results | Publications

Short Description

FIDASIM-X is an extension of FIDASIM that repurposes its Monte Carlo neutral transport engine [1,2] to produce an integrated whole-device kinetic neutral transport solver. The code accepts spatially local 3D-in-v plasma distribution functions, equilibrium fields, plasma profiles, neutral source specifications, and vacuum vessel geometry as inputs. It solves the neutral linear Boltzmann transport equation, and returns neutral density distributions together with self-consistent plasma source and sink operators suitable for coupling to kinetic transport solvers such as CQL3D. Within the CompX integrated modeling environment, this capability enables self-consistent simulations that combine RF wave propagation and absorption, neutral beam injection, kinetic plasma transport, and vessel-scale neutral gas transport, providing a unified treatment of plasma-neutral interactions in realistic magnetic confinement devices. The aim is to fully track the interacting plasma and neutral species distributions.

Date/Active Use

2025

Authors

Juan Caneses-Marin, with help from the FIDASIM group.

Language

F77/F90 + MPI +Python

Purpose/Function/Special Features

The purpose is for calculation of neutral species transport in 6D configuration space consistent with nonthermal electron and ion plasmas in tokamaks and open magnetic systems.

Basic Algorithms

Equilibrium geometry is specified by analytical formulas and by the eqdsk format files.

Coupled Diagnostics

Neutral distribution and the CQL3D suite of diagnostics are available.

Key Results

Please see Ref. [3], below, for first results from FIDASim-NT. Recent work is presented at https://github.com/D3DEnergetic/FIDASIM/tree/jfcm/mirror_equilib .

Selected Publications, and References

B. Geiger et al., “Progress in modelling fast-ion D-alpha spectra and neutral particle analyzer fluxes using FIDASIM,” Plasma Phys. Control. Fusion, vol. 62, no. 10, p. 105008, Aug. 2020, doi: 10.1088/1361-6587/aba8d7. <\a>
W. W. Heidbrink, D. Liu, Y. Luo, E. Ruskov, and B. Geiger, “A Code that Simulates Fast- Ion Dα and Neutral Particle Measurements,” Communications in Computational Physics, vol. 10, no. 3, pp. 716–741, Sep. 2011, doi: 10.4208/cicp.190810.080211a. <\a>
J. F. Caneses-Marin, R. W. Harvey, Y. V. Petrov, B. Biswas, and S. J. Frank, “Kinetic Modeling of Neutral Beam and Edge Neutrals in Plasma Confinement Devices Using FIDASIM and CQL3D-M,” presented at the 66th Annual Meeting of the APS Division of Plasma Physics, Los Angeles, California, 2025. Accessed: Jan. 31, 2026. [Online]. Available: https://archive.aps.org/dpp/2025/cp13/176/ <\a>