Therefore, any reliance you place on such information is strictly at your own risk. We make no representations or warranties of any kind, express or implied, about the completeness, accuracy, reliability, suitability or availability with respect to the website or the information, products, services, or related graphics on the website for any purpose. While we endeavour to keep the information provided up to date, and as accurately as possible, your use is entirely at your risk, for which shall not be liable whatsoever. These experiences are relevant to JT-60SA, ITER, and to the rest of the fusion community.Disclaimer All information and any services provided from, its subdomain or all other pages under this domain are on an "as-is" and "as-available" basis without warranties of any kind and are made available for your general information and use only. Repairing the device and designing contingency plans brought out the best in all of us and reminded us that what matters most is the value and importance of lessons learned. “There has been an incredible amount of collaboration through technical discussions a stronger involvement of F4E seconding staff to Japan, and the valuable contribution of IPP, CEA, KIT, Wendelstein 7X, QST. For Enrico Di Pietro, Head of F4E JT-60SA Unit, the technical setback was an opportunity to realign the work forces of the project and to bring out the best from all parties. This new system is currently under development as JT-60SA is planned to restart cool down operations and energisation in March 2023 aiming for first plasma later in the year. Technicians performing repairs inside the cryostat of JT-60SA, Naka, Japan, November 2022 © QST They opted for an early detection leak system in the cryostat to ensure that all energy contained in the magnets will be dumped before the pressure reaches dangerous levels for the device. To address this new challenge the team of experts started considering workarounds and changed strategy. Although this operation was successful in terms of logistics, it revealed low voltage holding in new parts of the machine. From August until September, they performed Paschen tests, which consist of energising all magnet circuits under controlled vacuum. For instance, some weaknesses were identified in the factory insulation of the equilibrium coils and the central solenoid, part of the magnets system that would confine the hot plasma, manage its shape and stability. In some cases, repairing this equipment was going to be difficult given the limited access in the device and the risk of a further delay for first plasma operations. Teams of engineers from Europe and Japan during meetings for the qualification of mock-ups for JT-60SA, Naka, Japan © F4E These efforts started in May 2021 and lasted roughly a year, counting on the involvement of F4E and other experts from Europe and Japan, in validating root causes and carrying out repairs. To the JT-60SA team, however, it was a period of reflection by joining forces to fix the device and deliver. To many this would have been a blow to their motivation. In total, 90 locations needed to be repaired and the machine sensors had to be rewired. Nevertheless, they did produce helium leakage and the machine was shut down.Īs a result of this incident, a thorough analysis was conducted, and the circuit was attributed to areas where electrical insulation was performed manually. Engineers took immediate action and concluded that damages were limited, since the incident happened at low current. But an unexpected turn of events in March changed all plans due to a short circuit at the terminals of one of the machine’s largest poloidal field coils measuring more than 12 m in diameter. The Toroidal Field coils, supplied by the EU, had successfully reached the maximum current of 25 700 ampere, and a first Electron Cyclotron Resonance Heating plasma had been produced. The first results were reassuring and in line with machine’s design. Towards the end of 2020 the team of engineers started testing its performance aiming for the big crescendo in the first quarter of 2021. In 2021, after almost 11 years from the production of its first pieces of equipment, the device was ready to be switched on. The sound project management and the absence of any political wrangling have shaped the ethos of this project. This scientific partnership has received praise for its smooth, dynamic, and efficient modus operandi. JT-60SA is the fruit of collaboration between Europe and Japan relying on the know-how of laboratories, and companies determined to test further the various technologies to harness fusion. In the chain of knowledge, it would provide answers and lessons that would feed into ITER-next in line to take the lead. When the scaffolding of JT-60SA was lifted, after assembly was completed, there was heightened anticipation in the fusion community that scientists would soon start to operate the most powerful fusion device to date.
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