The ITER Organization has achieved a critical commissioning milestone by cooling the first of its 18 toroidal field (TF) magnets to its cryogenic operating temperature. The 330-ton niobium-tin (Nb3Sn) superconducting coil was brought down to 4.5 Kelvin (-269 °C) over approximately one month inside the site's Magnet Cold Test Facility. This procedure is a necessary precursor to the high-current tests that will validate the magnet's performance before its final installation into the tokamak pit. The successful cooldown demonstrates the functionality of the complex cryogenic systems designed to handle the massive thermal loads of the magnet array, a key step in the assembly of the world's largest tokamak. Source: ITER

Each TF coil stands 17 meters high and 9 meters wide, forming the primary magnetic cage for the fusion plasma. When energized, the complete set of 18 coils will generate a peak magnetic field of 13 Tesla on the plasma axis, essential for confining the 150-million-degree Celsius D-T fuel. The choice of Nb3Sn superconductor is critical for achieving such high field strengths, but it requires the extreme cold to eliminate electrical resistance. The successful operation of the test facility's helium cryoplant and associated thermal shielding is therefore as significant as the performance of the magnet itself, validating a core technology for the ITER program. Source: ITER

Each TF coil stands 17 meters high and 9 meters wide, forming the primary magnetic cage for the fusion plasma.

The cooling process involved a carefully controlled sequence using both gaseous and liquid helium. Engineers first circulated gaseous helium to gradually remove the vast amount of stored thermal energy from the 330-ton structure, a month-long process to avoid inducing damaging thermal stresses. Once the coil reached an intermediate cryogenic temperature, liquid helium was introduced to complete the cooldown to 4.5 K. This test serves as a full-scale dress rehearsal for the procedures that will be used for the remaining 17 TF coils, streamlining the assembly and commissioning phase of the main device. This milestone is a significant de-risking event for the project's complex magnet systems, which represent a substantial portion of the overall construction effort. Source: ITER

With the coil at its operational temperature, the next phase involves a series of high-current trials. Engineers will ramp up the electrical current in the superconductor to its nominal value of 68,000 amperes. These tests are designed to confirm the magnet's structural integrity under immense electromagnetic forces and to verify its superconducting performance, including its stability against quenches. Data from these trials will be used to qualify the manufacturing and assembly processes for all TF coils, which have been produced by consortia in Europe and Japan. The successful completion of these power tests will clear the component for installation, marking a tangible step forward in the machine's assembly and bringing the prospect of a burning plasma experiment closer to reality. Source: ITER