Over the last 36 hours, another vacuum vessel sector was inserted into the ITER tokamak assembly pit. Five of nine sectors—over half of the plasma chamber—are now in place. Great journeys are comprised of small steps. The transfer of sector module #4 into the ITER tokamak pit this week involved a meticulous lifting protocol that featured nine hours of pre-lift tests and verifications, 12 hours of transfer time to the pit, and another 15 hours of ultra-precise landing manoeuvres to ensure the component reached its final destination.“This lift was successful because of the excellent work being done at every step of the operation,” says Mathieu Demeyere, the principal construction manager who supervised the operation for ITER. “The level of preparation and the reactivity of the teams meant we could adapt to the different challenges that arose during the lift and complete another safe landing.”The pre-lift protocol was launched at 6:00 a.m. on Tuesday 26 May when metrology was confirmed and operators slowly increased the tension in the lines connecting the sector module to the overhead cranes. The next steps included a 90 mm test lift that allowed certain sensors to be removed. Then, the lashing securing the sector module in the sector sub-assembly tool was released and the module was given another test lift to 500 mm. Before the lift begins, metrology and the sector module's weight distribution are verified from a temporary command centre in the Assembly Hall. After a final metrology check confirmed there were no clashes, the module was extracted just before 3:00 p.m. on Tuesday and guided carefully to the tokamak pit and lowered by the overhead cranes. It arrived 500 mm above its final landing position at 3:00 a.m. on Wednesday 27 May. Then came the work of reconnecting sensors, installing lashing, and verifying again there were no clashes.The final hours were spent aligning the sector module with its gravity supports, bringing it into contact with the TIPI tables (for toroidal field coil in-pit installation tool), and tightening the bolts before its full weight was finally released from the overhead cranes shortly after 6:00 p.m. Before the weight of the sector module could be released from the overhead crane, it had to be perfectly aligned. Like its predecessors in the pit, sector module #4 landed ahead of the schedule foreseen in the ITER Baseline, as lessons learned continue to contribute to greater efficiency and time saved. With sector module #7, it took 7.4 months to complete the assembly of the module from the time the vacuum vessel sector arrived in tooling to the time it landed in the tokamak pit in April 2025. With sector module #4, this process was reduced to 5.5 months.“There is a learning curve effect that was expected but it is materializing more quickly than anticipated and we are seeing the results right now,” says Nicolas Sapet, the ITER project leader for sector module sub assembly. “The progress is thanks to the lessons learned from the experience acquired by the teams.”  With the fifth sector module in place, 200 degrees of the plasma chamber are now in position. This latest installation milestone brings the plasma chamber to more than half complete. Vacuum vessel sectors #4, #5, #6, #7 and #8 now stand aligned side by side in the tokamak pit. A sixth sector module is scheduled for installation this summer on the opposite side of the machine, and a seventh is expected before the end of the year.

Under clement skies and with millimetre precision, ITER assembly teams once again carried out a rare heavy-lifting operation outdoors, rotating a 400-tonne vacuum vessel sector using a temporary gantry crane. For the third time, the ITER machine assembly team has used an outdoor gantry crane to expose the underside of a recently delivered vacuum vessel sector.The challenge in 2025 was logistical as much as technical. With vacuum vessel assembly back underway, the Assembly Hall’s lifting and handling equipment was already fully committed to the transport, upending and positioning of sector modules under construction. Freeing up the equipment needed to rotate newly arrived sectors would have risked slowing assembly progress and reducing the schedule gains teams had built against the ITER Baseline.Instead, engineers devised an alternative solution: move the operation outdoors.Weather permitting, teams could temporarily install a gantry crane capable of lifting 400 tonnes and perform the rotation in open air. Twice in 2025, and again last week, this all-day operation was successfully carried out under the most stringent safety conditions.For the first two sectors, temporary lifting lugs had to be welded onto the components before rotation could begin. This time, however, the European Domestic Agency anticipated the operation and welded the lifting lugs onto vacuum vessel sector #3 before it left the factory. As a result, the sector could be rotated just six days after arriving on site.With the rotation complete, vacuum vessel sector #3 has now returned to a workshop on site for repair to its bevel joint surfaces before rejoining ITER’s advancing machine assembly campaign.See the 12-hour rotation operation sped up to a few seconds, below.

Operations have begun at the ITER magnet cold test facility, where selected superconducting magnets will be tested at their operating temperature of 4 K and up to full current before installation in the machine. The successful cooldown of the first magnet coil to 4 Kelvin (K), or minus 269 °C, was announced on Thursday. Members of the ITER Council Management Advisory Committee attending a May meeting on site joined the technical teams in the ITER control room for a small ceremony marking the achievement.The first magnet coil to undergo testing is 330-tonne ITER toroidal field coil #07 (TF07). Additional toroidal field coils from different manufacturers will follow, along with one ring-shaped poloidal field coil—ITER’s smallest, PF1.Although no external test can fully reproduce operating conditions inside the ITER machine, tests in the magnet cold test facility will provide essential information on magnet behaviour, cryogenic performance, electrical interfaces, instrumentation, and the critical joints that connect the layers of wound superconductor inside of the magnet coils, and strengthen ITER’s risk mitigation and readiness.Specific objectives include the validation of high-voltage ground insulation at different temperatures, the demonstration of critical quench* detection capabilities, and the verification of coil performance at nominal current (68 kA for the toroidal field coils and 48 kA for PF1). The campaign will also test instrumentation chains, control logic systems, and key magnet protection functions.  On Thursday 21 May, members of the ITER Council Management Advisory Committee visit the ITER control room and meet the team supervising the operation of the ITER magnet cold test facility. The ITER magnet cold testing program was launched in 2023 as part of ITER’s revised approach to assembly and commissioning. The facility, built in record time, is located in a building previously used by the European Domestic Agency to manufacture ITER’s four largest poloidal field coils, and it takes advantage of the building’s scale, lift equipment, and proximity to the cryoplant. â€œITER as a first-of-a-kind project requires ingenuity as well as discipline,” said ITER Director-General Pietro Barabaschi. “By repurposing existing infrastructure, using the capabilities of our cryoplant, and mobilizing a multidisciplinary team, we have created a practical way to reduce risk before integrated commissioning. This is important for ITER as well as an example of how ITER can support the wider fusion ecosystem by creating knowledge, infrastructure, and operational experience that others can use.”Following the testing of multiple ITER magnet coils, the magnet cold test facility will be made available to other fusion stakeholders as part of the ITER Organization’s knowledge-sharing and engagement initiatives with the private fusion sector. (See more about the Private Sector Fusion Engagement program here.)*Superconductivity can be maintained in the magnet coils as long as certain threshold conditions are respected (cryogenic temperatures, current density, magnetic field). Outside of these boundary conditions, a magnet will return to its normal resistive state and the high current will produce high heat and voltage. This transition from superconducting to resistive is referred to as a quench. See the press release issued on 21 May. Once the lid was placed over the cryostat, it took 12 days to reach the nominal magnet operating temperature of 4 K (-269 °C). Next, the first coil to be tested will be progressively energized up to full current (68 kA).

Robots, teamwork and creativity took centre stage at the Marie Mauron junior high school in Pertuis, France, on 21 May, as students gathered for the 15th edition of the ITER Robots competition. Organized by Agence Iter France in partnership with the Aix-Marseille education authorities, the ITER Organization and the French Alternative Energies and Atomic Energy Commission (CEA), ITER Robots is a robotics engineering competition for primary and secondary students in the south of France.This year’s edition brought together 315 students, in 25 teams from 19 schools. Over the course of the six months preceding the competition, participants had designed and built small-scale robots capable of simulating maintenance operations inside the ITER tokamak.Throughout the day, teams tackled a series of demanding robotics challenges that tested their technical expertise, ingenuity and collaborative skills, while also deepening their understanding of robotics, fusion energy, and the ITER project.Since its launch, the competition has steadily grown in popularity and is now regarded as a flagship educational event in the region.  315 students in 25 teams from 19 schools took part in the 15th edition of the ITER Robot contest. ITER engineer Jean-Pierre Martins, a jury member since the competition’s early years, highlighted the complexity of the challenges.“I have been a member of the jury for 15 years now. The contest is not an easy one—especially the activity that asks students’ robots to replicate ITER-like remote handling operations, transporting tokamak components from the reactor to the ITER Hot Cell Facility for repair or refurbishment,” he said. “This year, we did not award a prize in this category, but I do not see that as a failure. Things do not always go as planned, but every setback brings valuable experience and opportunities to grow.”Fabrice Raynal of Agence Iter France echoed this message of perseverance and collective achievement. Addressing the students, he praised their commitment and teamwork.“Through your work, your team spirit and your dedication, you have shown that together you are capable of taking on complex challenges, just like the engineers working at ITER,” he said.See the gallery below for some more impressions from the day.