JT-60SA
JT-60SA (Japan Torus-60 Super Advanced) is the world’s largest superconducting tokamak currently in operation. Located at the National Institutes for Quantum Science and Technology (QST) in Naka, Japan, it represents a joint project between Japan and the European Union under the Broader Approach Agreement.
From JT-60 to JT-60SA
Section titled “From JT-60 to JT-60SA”The Legacy of JT-60
Section titled “The Legacy of JT-60”JT-60, which operated from 1985 to 2008, achieved numerous world records:
- Highest fusion triple product for a tokamak
- Equivalent breakeven (Q = 1.25 with D-D extrapolated to D-T)
- Long-pulse operation over 28 seconds
- Advanced plasma modes with high bootstrap current fraction
JT-60SA builds on this legacy while introducing superconducting magnets for long-pulse operation.
Key Upgrades
Section titled “Key Upgrades”| Feature | JT-60 | JT-60SA |
|---|---|---|
| Magnet type | Copper (normal conducting) | Superconducting |
| Plasma current | 6 MA | 5.5 MA |
| Pulse length | 28 s (limited) | 100 s (target) |
| Plasma volume | 80 m3 | 133 m3 |
| Heating power | 40 MW | 41 MW |
Japan-EU Collaboration
Section titled “Japan-EU Collaboration”JT-60SA is a central project of the Broader Approach Agreement, signed in 2007 between Japan and Euratom. The agreement complements ITER by developing technologies that will accelerate fusion energy development.
Division of Contributions
Section titled “Division of Contributions”Japan (QST)
- Host facility and infrastructure
- Vacuum vessel
- Thermal shields
- Cryostat
- Cryogenic system
- Power supply system
European Union (Fusion for Energy)
- Superconducting magnets (TF and EF coils)
- Cryostat base
- Power supply components
- Diagnostics and heating systems
Role as ITER Satellite Tokamak
Section titled “Role as ITER Satellite Tokamak”JT-60SA serves critical functions in supporting ITER:
Plasma Scenario Development
Section titled “Plasma Scenario Development”- Developing and optimizing plasma scenarios before ITER operation
- Testing high-beta advanced plasma configurations
- Investigating disruption avoidance and mitigation techniques
Personnel Training
Section titled “Personnel Training”- Training scientists and engineers for ITER operation
- Providing hands-on experience with large superconducting tokamaks
- Building international collaboration culture
Risk Reduction
Section titled “Risk Reduction”- Identifying potential issues before ITER encounters them
- Testing components and systems in an integrated environment
- Developing operational procedures
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value |
|---|---|
| Plasma major radius | 2.96 m |
| Plasma minor radius | 1.18 m |
| Aspect ratio | 2.5 |
| Plasma current | 5.5 MA |
| Toroidal field (at R = 2.96 m) | 2.25 T |
| Plasma volume | 133 m3 |
| Pulse length | 100 s (typical), 300 s (reduced current) |
| Total weight | 2,800 tonnes |
Heating Systems
Section titled “Heating Systems”- Neutral Beam Injection: 34 MW (500 keV negative ion beams)
- Electron Cyclotron Heating: 7 MW
- Total heating power: 41 MW
First Plasma Achievement (October 2023)
Section titled “First Plasma Achievement (October 2023)”On October 23, 2023, JT-60SA achieved first plasma, marking a major milestone in fusion research. This success came after:
- Assembly completion in March 2020
- Comprehensive integrated commissioning tests
- Superconducting magnet cooling to 4.5 K
- Systematic vacuum vessel preparation
The first plasma represented the culmination of over a decade of construction and international collaboration.
Research Program
Section titled “Research Program”Phase 1: Initial Operation
Section titled “Phase 1: Initial Operation”- Commissioning of all systems
- Characterization of plasma behavior
- Exploration of operating space
Phase 2: Advanced Plasma Development
Section titled “Phase 2: Advanced Plasma Development”- High-beta steady-state plasmas
- Advanced divertor operation
- Testing of plasma control systems
Phase 3: ITER Support
Section titled “Phase 3: ITER Support”- Developing scenarios relevant to ITER
- Risk mitigation studies
- Preparing for D-T operation
Scientific Objectives
Section titled “Scientific Objectives”JT-60SA addresses several key research questions:
High-Beta Plasma Confinement
Section titled “High-Beta Plasma Confinement”Achieving normalized beta (betaN) above 4 to demonstrate advanced tokamak scenarios.
Steady-State Operation
Section titled “Steady-State Operation”Maintaining plasma for 100 seconds with dominant non-inductive current drive.
Divertor Performance
Section titled “Divertor Performance”Testing divertor configurations for heat flux handling relevant to ITER and DEMO.
Disruption Control
Section titled “Disruption Control”Developing techniques to predict, avoid, and mitigate disruptions.
Significance for Fusion Development
Section titled “Significance for Fusion Development”JT-60SA bridges the gap between current tokamak research and ITER/DEMO:
- Validates superconducting tokamak technology at scale
- Develops advanced plasma scenarios for future reactors
- Trains the next generation of fusion scientists
- Strengthens international collaboration framework
As the world’s largest operating superconducting tokamak, JT-60SA will provide invaluable data and experience for the fusion community for years to come.