ITER Completes World's Most Powerful Fusion Magnet

After **15 years of unprecedented engineering challenges**, General Atomics has completed the world's most powerful pulsed magnet system for nuclear fusion. The **central solenoid** represents humanity's most ambitious attempt to cage plasma hotter than the sun's core, with magnetic forces powerful enough to levitate naval vessels. ## The ITER central solenoid generates **13 Tesla magnetic fields** from six modules weighing **1,000 tons combined**, making it the strongest fusion magnet ever built. Each module required **6 kilometers** of niobium-tin superconducting cable wound with millimeter precision over **two years** of fabrication. This achievement marks a critical milestone for the **$25 billion ITER project** in southern France, bringing the 35-nation collaboration closer to demonstrating [fusion as a viable clean energy source](/science/nuclear-fusion-breakthroughs-clean-energy-2025) for humanity's future. --- ## Engineering the Impossible: 15 Years of Innovation General Atomics' Magnet Technologies Center in Poway, California transformed from a conventional facility into a specialized manufacturing powerhouse capable of building components that push the boundaries of physics and materials science. The central solenoid project began in 2010 with a formidable challenge. No existing facility could manufacture magnets at this scale with the required precision. The team designed **novel tools** and **purpose-built equipment** specifically for this single application. Key manufacturing achievements include: - **6 individual modules**: Each weighing **270,000 pounds** and standing **14 feet wide** - **59-foot total height**: When stacked, taller than a five-story building - **6 kilometers of cable per module**: Niobium-tin superconductor jacketed in steel - **Millimeter-level precision**: Required across multi-ton components during assembly The final module completed fabrication in **April 2025**, with all six modules now ready for shipment to the ITER facility in Cadarache, France. Five modules have already arrived at the site, while the sixth is en route. > "GA is proud to be leading the way in developing technologies needed to make fusion power a reality." > > — **Dr. Wayne Solomon**, General Atomics --- ## Niobium-Tin: The Superconductor That Almost Broke Physics The central solenoid's extraordinary performance depends entirely on **niobium-tin** (Nb3Sn), a superconducting material as brittle as glass yet capable of conducting massive electrical currents without resistance at cryogenic temperatures. Manufacturing with niobium-tin presented challenges that nearly derailed the project. Unlike conventional **niobium-titanium** superconductors that can be wound and shaped after processing, niobium-tin becomes extremely fragile once formed. Engineers had to develop entirely new fabrication sequences. The innovative solution involves separating niobium and tin components inside the cable during winding, then forming the superconducting compound through **reactive diffusion** at extreme temperatures after the coil reaches its final shape. Manufacturing complexities include: - **Heat treatment duration**: **10.5 days at 570°C**, plus **4 days at 650°C** - **Total furnace time**: Nearly **5 weeks** per module for thermal processing - **Thermal cycle tolerance**: Must survive **60,000 cycles** without degradation - **Global supply scaling**: ITER required increasing worldwide niobium-tin production from **15 tons/year** to **100 tons/year** The cost and complexity meant prototyping wasn't feasible. Engineers had to achieve perfection on the first attempt with each module, with no room for error on components worth tens of millions of dollars. --- ## Magnetic Force That Could Lift Aircraft Carriers The completed central solenoid will generate magnetic fields **280,000 times stronger** than Earth's natural magnetic field. At its core, the **13 Tesla** peak field strength creates forces that defy everyday intuition. To put this power in perspective, the solenoid's magnetic force is theoretically strong enough to lift a **Nimitz-class aircraft carrier** approximately **6 feet** into the air. While this dramatic comparison illustrates the engineering achievement, the magnet's actual purpose is far more sophisticated. The central solenoid serves as the "beating heart" of ITER's tokamak reactor, performing critical functions: - **Plasma initiation**: Creates the initial magnetic field to ignite fusion reactions - **Plasma current drive**: Induces millions of amperes of current in the plasma - **Plasma shaping**: Provides precise control over the plasma's position and stability - **Pulsed operation**: Delivers rapid magnetic field changes to sustain fusion conditions The magnet must maintain these extreme fields while operating at **150 million degrees Celsius** in the surrounding plasma, temperatures ten times hotter than the sun's core. This thermal extreme occurs just meters away from the superconducting coils cooled to **-269°C** (4 Kelvin). Engineering this temperature differential represents one of fusion's greatest technical challenges, requiring advanced thermal shielding and vacuum insulation systems. --- ## Assembly Timeline and ITER Integration With manufacturing complete, the project enters its crucial assembly phase. The six central solenoid modules will be stacked vertically in the heart of ITER's tokamak, forming a unified magnetic system that coordinates with **18 toroidal field magnets** and **6 poloidal field coils**. ITER's revised assembly schedule includes: - **2025-2027**: Central solenoid module stacking and integration - **2027**: Vacuum vessel completion and hermetic sealing - **2034**: Full plasma current achievement - **2035**: First plasma operations with deuterium-deuterium fuel - **2039**: Deuterium-tritium fusion operations at full power The central solenoid's completion removes a critical uncertainty from this timeline. As the most technically complex magnetic component, its successful manufacture validates the entire magnet systems approach. The **6.4 gigajoules** of stored magnetic energy in the central solenoid must be precisely coordinated with the other magnet systems, requiring sophisticated control systems and fail-safe mechanisms. This energy storage capacity equals approximately **1.5 tons of TNT**, emphasizing the importance of safety systems. [Advanced materials breakthroughs](/science/room-temperature-superconductor-confirmed) continue enabling fusion progress, while [private fusion companies](/science/iter-2025-fusion-assembly-breakthrough-race) race toward earlier demonstration timelines. --- ## Global Supply Chain Coordination Building the central solenoid required unprecedented international cooperation across the superconductor supply chain. The project involved **eight U.S. suppliers** providing **9,000 individual parts**, each manufactured to tolerances measured in microns. Supply chain achievements include: - **Superconductor strand production**: Multiple manufacturers in the U.S., Europe, Russia, and China - **Steel jacket fabrication**: Specialized mills producing high-strength containment - **Insulation materials**: Advanced ceramics and polymers rated for extreme conditions - **Instrumentation sensors**: Thousands of temperature and strain gauges embedded in windings Coordinating this global effort while maintaining quality standards proved as challenging as the engineering itself. **COVID-19 pandemic disruptions** in 2020-2021 threatened critical delivery schedules, requiring adaptive manufacturing strategies and alternative sourcing. The successful navigation of these supply chain challenges demonstrates fusion's maturation from laboratory science to industrial-scale engineering. Future commercial fusion reactors will build on these established supply networks and manufacturing capabilities. --- ## What This Means for Fusion's Future The central solenoid's completion represents more than a single magnet system. It validates that private companies can successfully manufacture fusion components at the scale required for commercial power plants. General Atomics' achievement provides crucial confidence for the emerging private fusion industry. Companies like **Commonwealth Fusion Systems** and **TAE Technologies** are designing next-generation reactors that will require similar superconducting magnet technology. Key implications include: - **Manufacturing scalability**: Proven techniques can be adapted for commercial fusion plants - **Cost reduction pathway**: Serial production will decrease per-unit costs significantly - **Supply chain maturity**: Global niobium-tin production now supports multiple projects - **Risk reduction**: Successful completion lowers technical uncertainty for future projects The **$180 million Westinghouse contract** for ITER's vacuum vessel assembly, signed in June 2025, builds on this momentum. Major industrial contractors now view fusion as a viable business opportunity rather than speculative research. ITER's first plasma in **2035** will provide critical validation data for the entire fusion industry, testing the central solenoid under real fusion conditions and verifying performance models developed over decades of research. The transition from **50 megawatts of input power** to **500 megawatts of fusion output** represents the energy gain ratio (Q=10) that will prove fusion's commercial viability. The central solenoid makes this demonstration possible. ## Sources 1. [General Atomics Central Solenoid Completion](https://www.ga.com/ga-marks-completion-of-the-world-s-largest-and-most-powerful-pulsed-superconducting-magnet-for-fusion-energy) - Official announcement and technical specifications 2. [ITER Magnet System Details](https://www.iter.org/machine/magnets) - Central solenoid integration and magnetic field specifications 3. [Niobium-Tin Manufacturing Challenges](https://www.iter.org/newsline/-/1908) - Superconductor production scaling and material properties 4. [ITER Timeline Update](https://www.world-nuclear-news.org/articles/iter-s-proposed-new-timeline-initial-phase-of-oper) - Revised assembly schedule and first plasma projections 5. [Magnet Engineering Challenges](https://physicsworld.com/a/magnet-challenges-for-iter/) - Technical obstacles and solutions in superconducting magnet fabrication