fusionsimulator.io
A real-time tokamak plasma simulator that runs entirely in your browser.
fusionsimulator.io combines a Rust physics engine (compiled to WebAssembly) with a
React/TypeScript frontend to provide an interactive control room experience
for exploring tokamak plasma behavior.
Features
- Four tokamak devices: DIII-D, JET, ITER, and CENTAUR (conceptual
negative-triangularity) with device-specific geometry, heating systems,
and engineering limits
- Three pulse presets per device: H-mode, L-mode, and Density Limit
scenarios with realistic waveform programming
- Real-time physics: 0D power balance transport, analytic Grad-Shafranov
equilibrium, tanh-pedestal profiles, ELM dynamics, and disruption modeling
- Interactive control room: 2D equilibrium cross-section, 19-channel time
trace viewer, plasma parameter dashboard, and 3D tokamak port view
- Pulse Planner: Edit pulse parameters (Ip, heating power, density,
shaping) and run custom scenarios
- Fusion diagnostics: Computed fusion power/Q, neutron rate, divertor heat
flux with surface temperature modeling
- Post-pulse analysis: Time scrubbing, radial profile viewer with
synthetic Thomson scattering
- Impurity seeding: Nitrogen, neon and argon gas lines per machine, with
ADAS cooling curves for core radiation, Z_eff and dilution, a
Goldston-Reinke-Schwartz detachment threshold, and a radiating divertor
front tinted by the seeded species
- Pulse record: Persistent pulse numbers, an append-only event log with
alarm severities, a named cause and operator action for every disruption,
an achieved-versus-programmed report, and the previous pulse as a reference
trace
Physics Models
The simulator implements peer-reviewed physics models from the fusion literature:
| Model | Reference |
|---|
| MHD equilibrium | Cerfon-Freidberg analytic Grad-Shafranov (PoP 2010) |
| Energy confinement | IPB98(y,2) scaling (ITER Physics Basis, NF 1999) |
| L-H transition | Martin power threshold scaling (JPCS 2008) |
| Beta limit | Troyon normalized beta limit (PPCF 1984) |
| Density limit | Greenwald limit (PPCF 2002) |
| Fusion reactivity | Bosch-Hale parameterization (NF 1992) |
| Divertor heat flux | Eich SOL width scaling (NF 2013) |
| Radial profiles | OMFIT tanh-pedestal parameterization |
For complete citations and equations, see the in-app Bibliography page.
Disclaimer: fusionsimulator.io uses 0D scaling laws and analytic approximations.
It is an educational and visualization tool, not a predictive transport code.
Getting Started
Prerequisites
Quick Start
# Clone the repository
git clone <repo-url>
cd fusion-sim
# Full build (WASM engine + frontend)
./build.sh
# Serve the built app
cd web && npx vite preview
Development
# Build WASM module
wasm-pack build crates/tok-sym-core \
--target web \
--out-dir ../../web/src/wasm \
--no-default-features \
--features wasm
# Start frontend dev server (with hot reload)
cd web
npm install
npm run dev
The dev server runs at http://localhost:5173 by default.
Running Tests
# Rust physics engine tests (full-pulse tests are slow in debug; use --release)
cargo test --release -p tok-sym-core
# Envelope sweep: every planner control at five levels on every device and
# preset, run through the engine and checked for plausibility (~5 min on 6
# cores). Regenerate the program matrix whenever a preset, a slider range or
# the program builder changes; the matrix check fails when it is stale.
cargo test --release -p tok-sym-core --test envelope -- --nocapture
cd web && npm run matrix:emit && npm run matrix:check
# TypeScript type checking
cd web && npx tsc -b
# Lint
cd web && npm run lint
Generating Rust API Docs
cargo doc -p tok-sym-core --no-deps --open
This opens the auto-generated API documentation for the physics engine in
your browser. All public types and functions are documented with rustdoc
comments.
Project Structure
fusion-sim/
├── crates/tok-sym-core/ Rust physics engine (~5,500 lines)
│ └── src/
│ ├── equilibrium.rs Cerfon-Freidberg Grad-Shafranov solver
│ ├── transport.rs 0D power balance (IPB98, L-H, ELMs)
│ ├── profiles.rs Tanh-pedestal radial profiles
│ ├── devices.rs DIII-D, JET, ITER, CENTAUR definitions
│ ├── disruption.rs Disruption risk & dynamics
│ ├── diagnostics.rs Synthetic diagnostic signals
│ ├── contour.rs Marching squares contour extraction
│ ├── simulation.rs Top-level orchestrator
│ └── wasm_api.rs WASM-bindgen API surface
│
├── web/ React frontend (~11,600 lines)
│ └── src/
│ ├── lib/ Shared libraries (WASM init, hooks, physics)
│ ├── components/ UI components (canvas, panels, 3D view)
│ ├── pages/ Route pages (DeviceSelect, ControlRoom, etc.)
│ └── wasm/ Generated WASM output
│
├── build.sh Full build script
└── ARCHITECTURE.md Comprehensive architecture guide
For detailed documentation of every module, function, and component, see
ARCHITECTURE.md.
Tech Stack
- Physics engine: Rust, compiled to WebAssembly via wasm-pack
- Frontend: React 19, TypeScript 5.9, Vite 7.3
- Styling: Tailwind CSS 4.2
- 3D rendering: Three.js with custom GLSL shaders
- 2D rendering: HTML Canvas API
- Routing: React Router v7
Architecture Overview
┌─────────────────────────────────────────────────┐
│ Browser │
│ │
│ ┌──────────────┐ ┌────────────────────────┐ │
│ │ Rust/WASM │───▶│ React/TypeScript │ │
│ │ Physics │JSON│ │ │
│ │ Engine │◀───│ useSimulation hook │ │
│ │ │ │ │ │ │
│ │ • Equilibrium│ │ ├─ EquilibriumCanvas │ │
│ │ • Transport │ │ ├─ StatusPanel │ │
│ │ • Profiles │ │ ├─ UnifiedTracePanel │ │
│ │ • Disruption │ │ ├─ PortView (3D) │ │
│ │ • Contours │ │ └─ PulsePlanner │ │
│ └──────────────┘ └────────────────────────┘ │
└─────────────────────────────────────────────────┘
All physics runs in the WASM module. The TypeScript layer handles rendering,
user interaction, and some display-only derived computations (fusion Q,
divertor heat flux via Bosch-Hale and Eich scaling).
License
GNU General Public License v3.0 (GPL-3.0-only). See LICENSE for details.
Attribution
Developed by Daniel Burgess and the Columbia Fusion Research Center.
Copyright 2026 Daniel Burgess. Released under the GPL-3.0 license.
