Specialized Fusion Software

Our team combines experienced plasma scientists with professional software developers and machine learning engineers — building production-grade tools we use ourselves every day.

NSFsim Simulator

Our team actively develops NSFsim, an IMAS-compatible, advanced Grad–Shafranov 1.5D axisymmetric (2D solver with a 1D kinetic component), time-dependent, transport-modeling, free-boundary in external magnetic field tokamak plasma simulation code.

To take into account the details and provide reliable, self-consistent modeling, the tokamak digital replica is built from the geometrical and electrical characteristics of the magnetic system and passive conducting structures.

NSFsim has an unmatched set of capabilities that allow us to perform direct, inverse, and plasma-free calculations; develop discharge scenarios; simulate major disruptions and VDEs; perform equilibrium reconstruction; and much more.

Specialized Fusion Software

Simulation Software

For our work in tokamak simulation and design, plasma control, and diagnostics, we carefully select, license, and integrate the best available fusion codes. When something is missing or not good enough, we develop it ourselves — backed by our in-house physics team and collaborators from leading scientific organizations worldwide.

Online simulation platform

NSFsim simulations of DIII-D, ISTTOK, NSF NTT, SMART, and other tokamaks are available to the fusion community on the Fusion Twin Platform — a web service for running tokamak simulations and managing fusion data in the cloud.
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Public web API

The Fusion Twin Platform provides a public web API for running NSFsim simulations, developing and testing controllers, building automated pipelines, and more. Examples in Python and MATLAB are available on GitHub.
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Fusion data viewer

A free and open-source web application for exploring and visualizing fusion data stored in HDF5 files — with tree filtering, dataset inspection, and customizable dashboards for data analysis.
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Other codes coupling

TRAVIS (ECRH and ECCD ray-tracing), ASCOT5 (NBI and fast-particles), TGLF (turbulent transport), MISHKA (NN surrogate model for pedestal region), and other codes for consistent, end-to-end physics calculations.
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Open Source

We believe open tools strengthen the fusion community. Below are our publicly available repositories — free to use, fork, and contribute to.

Fusion Data Viewer

A backendless progressive web application for exploring and visualizing fusion data stored in HDF5 files—with tree filtering, dataset inspection, and customizable dashboards.
GitHub repository

Tokamak Replica Builder

A visual editor for drawing and configuring poloidal cross-sections of tokamak replicas for simulation. Available as a standalone web app and on FusionTwin.io.
GitHub repository

SOL Box Model

Reduced-physics 0D model of the tokamak Scrape-Off Layer (SOL). Given core power and particle fluxes plus magnetic geometry, it returns upstream (outer midplane, OMP) and divertor target plasma conditions.
GitHub repository

More coming soon

Follow us on GitHub for updates and new open source releases from the Next Step Fusion team. If you have any questions, we are always happy to discuss!
GitHub repository

Relevant Reading

We apply NSFsim and the framework around it to a wide range of problems — from code verification and experimental validation to machine learning for plasma control and scenario development.

Blog

Model Verification Using NSFsim: Plasma-free (Vacuum) Calculations

Collaboration with the CREATE team (University of Naples Federico II) on verifying NSFsim against their validated digital replica of the EAST tokamak using plasma-free vacuum shots.

Blog

NSFSim Perspective on Disruptions in Tokamaks — Part I: Physics Basis

Collaboration with the DTT project (led by ENEA) on disruption analysis, using NSFsim to simulate Major Disruption (MD) and Vertical Displacement Events (VDE) for mechanical load assessment.

Blog

6 Ways to Manage Your Fusion Data with Fusion Twin Platform

A practical guide to the data management capabilities of the Fusion Twin Platform — from running simulations and storing results to integrating experimental data and sharing workflows with your team.

Paper

Validation of NSFsim as a Grad-Shafranov equilibrium solver at DIII-D

Collaboration with the DIII-D National Fusion Facility — validating NSFsim as a Grad-Shafranov equilibrium solver, published in Fusion Engineering and Design.

Blog

Welcome the Fusion Twin Platform

Introducing the Fusion Twin Platform — a free web-based tool giving researchers, educators, and engineers access to pre-built digital tokamak replicas, powered by NSFsim and designed for simulation, ML exploration, and collaborative fusion research.

Blog

NSFsim: Validation and verification of synthetic magnetic diagnostics

Collaboration with the DIII-D National Fusion Facility — validating NSFsim's synthetic magnetic diagnostics against experimental data and GSevolve simulations across five plasma configurations.

See the publications page to learn more about our research and work.

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