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Central Solenoid

The US is responsible for 100% of the central solenoid (CS) magnet, including design, R&D, fabrication of 7 CS modules using supplied conductor (from Japan), associated structure, assembly tooling, bus extensions, and cooling connections.

The center solenoid is at the heart of the ITER tokamak.
The central solenoid is at the heart of the ITER tokamak. It both initiates plasma current and drives and shapes the plasma during operation. Image: US ITER

The central solenoid serves as the backbone of the ITER magnet system. The CS induces the majority of the magnetic flux change needed to initiate the plasma, generate the plasma current, and maintain this current during the burn time. The CS is made of six independent coil packs that use a niobium-tin (Nb3Sn) cable-in-conduit superconducting conductor, held together by a vertical pre-compression structure. The conductor will be produced in unit lengths up to 910 m. The US is responsible for the 6 modules of the CS, a spare module, and the structure that ties them together and links these modules to the rest of the magnet system.

How are we building one of the world's largest superconducting electromagnets for ITER? Watch Building the Heart of ITER.


For more information, contact Graham Rossano, US ITER Project Office Magnet Systems Team Leader (Acting), Oak Ridge National Laboratory, | 865-576-0104.

Fact Sheet

Turnover of module 1 of the central solenoid at General Atomics

Fabrication complete on 1st of 7 central solenoid modules

When ITER begins operations in 2025, its plasma will be initiated by the largest stacked pulsed superconducting magnet ever built—the ITER central solenoid. The US ITER magnets team, based at Oak Ridge National Laboratory, is overseeing the fabrication of the central solenoid modules, support structures, and assembly tooling. A major milestone was reached this spring when vendor General Atomics completed fabrication of the first of seven modules.

"General Atomics has done an outstanding job to reach the difficult and important milestone of completing module 1 fabrication," said Wayne Reiersen, US ITER Central Solenoid Magnets Team Leader. "This is the culmination of an eight-year effort involving concurrent engineering of the module design, the creation of a facility in which these powerful superconducting magnets could be built and tested, the qualification of the manufacturing processes, and the building of this first-of-a-kind module."

Source: ITER Newsline

A lower key block support with a technician at Petersen, Inc.

Delivery Begins of Lower Support Components for the “Heart of ITER”

Lower key blocks for the central solenoid are now being delivered to the ITER site

US ITER has started delivery of lower support structures for the central solenoid, the world’s largest electromagnet that will be at the center of the ITER fusion machine. The support structures provide a secure base and cage for the central solenoid in the face of thousands of tons of force. The first delivery, a lower key block weighing over 6 tons, was delivered in February to the ITER site in St. Paul-lez-Durance, France. Eight more lower key blocks are now being shipped. A total of 18 upper and lower key blocks will be delivered by the end of the year.

Module 1 of the central solenoid after vacuum pressure impregnation

Fabrication of Central Solenoid Module 1 Nears Completion

US ITER and contractor General Atomics recently achieved a major milestone in fabricating the ITER central solenoid, completing vacuum pressure impregnation (VPI) on the first production module. The VPI process is the penultimate step of fabrication that turns almost 6 km of carefully wound superconducting conductor into a structurally strong, electrically insulated electromagnet.

Source: ITER Newsline

Ground insulation was completed for the first central solenoid module.

Ground Insulation Completed on First Central Solenoid Module

Ground insulation ensures that each module is isolated from a potential fault of up to 30,000 volts from other systems and components in the ITER cryostat.


Central Solenoid and Assembly Platform drawing

A Symbolic First for the Central Solenoid

The central solenoid comprises six cylindrical modules plus structure subsets that will be assembled on site by the ITER Organization. Set to begin in 2019, delivery of all modules should be complete by 2021. The crate contains the main steel components of the central solenoid assembly platform—a thick steel structure that will be used throughout the assembly phase from early 2021 to mid-2023.


Central solenoid module in heat treatment

Central Solenoid Feels the Heat

The first of six independent magnets for ITER's central solenoid has successfully passed the heat treatment phase, which ultimately creates the solenoid's superconducting material. This milestone was reached in April at General Atomics (US), after the 110-tonne module spent just over ten days at 570 °C and another four at 650 °C.

Source: ITER Newsline