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
• Hall audio (opt-in): Synthesized machine sounds from the torus hall, driven by the live state: coil and converter hum at the site's mains frequency, flywheel generators sagging under load, beam-line noise, the cryoplant on superconducting machines, and the thud of a disruption. A separately labeled sonified D-alpha channel clicks once per ELM. Off by default; the plasma itself is silent
• Pulse sonification (opt-in): The pulse as sound, labeled as such: a converter whine whose pitch climbs with the current ramp and whose level follows the Ohmic drive power, a sub-100 Hz rumble from the power crossing the separatrix, a broadband roar that follows the divertor heat flux and surges when the divertor lights up at the L-H transition, and a neutron detector whose Poisson crackle gates the whole layer as the fusion power rises. A DD pulse ticks; a DT burn crackles
• 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

• Rust (stable toolchain)
• wasm-pack (cargo install wasm-pack)
• Node.js 18+ with npm

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.