ITER Organization Successfully Completes Half-Current Test of Toroidal Field Magnet

Recently, the magnet cold test facility of the ITER Organization successfully completed the cryogenic cold test of the second Toroidal Field (TF) coil. The heavy superconducting coil, numbered 17, was cooled to an extreme environment of 4K (minus 269 degrees Celsius) and then successfully energized to 34 kiloamperes (kA), reaching half of its 68kA rated operating current. The coil was then officially removed from the test bench and transferred to the assembly process of the main tokamak device.

As a standard unit of the ITER toroidal field magnet system, a single D-shaped TF coil is approximately 17 meters tall, about 9 meters wide, and weighs 330 tonnes, with windings made of advanced niobium-tin superconducting conductor and a design peak magnetic field of up to 11.8 tesla. Prior to this test, the engineering team had investigated and repaired a localized high-resistance defect at the feeder joint of the coil caused by oxidation of the contact surface, fully demonstrating the critical gatekeeping value of the cold test facility in intercepting interface-level defects and preventing “faulty integration” within the device.

This 34kA test focused on examining the actual deformation of the coil under stronger electromagnetic loads and precisely comparing it with the structural model. ITER Lead Mechanical Engineer Adrien Deydier noted that reaching this current threshold and confirming that the coil's operating behavior is highly consistent with model predictions is an important step in overall project advancement and has accumulated valuable experience for subsequent integrated commissioning. The earlier 10kA baseline functional test of Coil 7 conducted in May 2026 had already verified the joint resistance and quench detection system, while this half-current test represents a qualitative leap in the scale of verification.

With the successful delivery of Coil 17, the test facility has fully shifted to preparations for testing the spare Coil 19. According to the established engineering plan, Coil 19 will begin cooling in April 2027 and, after completing the 34kA stage, will be fitted with reinforcement structures to formally launch the assault on the 68kA full-current limit test. Subsequently, connection components identical to those inside the tokamak will be introduced and high voltage will be applied under sealed conditions, comprehensively verifying the magnet protection margin by simulating real disturbances, thereby building a solid technical defense line for the overall engineering acceptance of the world's largest fusion device.