First JT-60SA TF coil completed and delivered

Colleagues at F4E, CEA, ENEA and JAEA celebrated the delivery of the first JT-60SA Toroidal Field (TF) coil from the General Electric (GE) (formerly Alstom) factory in Belfort, France, to the Cold Testing Facility at CEA Saclay. “This outstanding achievement is the result of an intense, fruitful and efficient international collaboration between all parties involved in the JT-60SA project under the Broader Approach Agreement between Europe and Japan”, said Pietro Barabaschi, Home Team Project Manager for Europe’s contribution to the Broader Approach (BA) project. “We are especially grateful for the voluntarily contributions by France and Italy in making the JT-60SA TF coils become reality and congratulate CEA, the designated French contributor, responsible for the completion and delivery of this first TF coil”. Indeed, together with his team, Patrick Decool, JT-60SA Toroidal Field Coil Project Leader at CEA Cadarache has worked tirelessly for several years with members of the team led by Marc Nusbaum and Gérard Billotte at Alstom/GE, the company responsible for manufacturing the TF coil.

The TF Coils are one of the key components for the scientific success of any tokamak. They are gigantic “D” shaped superconducting magnets whose main task will be to create a magnetic cage where the plasma will be confined – that is to say, to keep the hot plasma from touching the walls of the vessel of the JT-60SA machine. To appreciate the challenges that have been overcome thus far it is enough to know that these superconducting coils for JT-60SA are among the largest in the world. Together the 18 coils, each 7 metres high and 4.5 metres wide, will produce a magnetic field of 2.25T at the core of the plasma.

The design activities for the TF coils took place during 2007-2011 and were widely shared between European and Japan Institutions: JAEA, F4E, ENEA and CEA. The manufacturing and testing of the TF coils, defined as European contributions to JT-60SA in the framework of the Broader Approach Agreement, were split in several lots, each requiring a high level of skill and quality.

F4E procured the superconducting strands manufactured by the Furukawa Company in Japan (completed in May 2013) and their subsequent cabling and jacketing to produce Cable-In-Conduit conductor by the Italian consortium ICAS (completed in October 2015). ENEA procured the TF coil casings manufactured by the company Walter Tosto. Using these components, CEA and ENEA, who each have the duty to produce, with a high level of accuracy and reliability, nine coils plus one spare, have placed industrial contracts with renowned superconducting coil manufacturers: Alstom/GE for CEA and ASG for ENEA.

The manufacturing process includes several steps which necessitate an unprecedented high level of precision and state of the art manufacturing tools. At each step the manufacturer has to complete a dedicated testing and quality control program. The TF coils are in work at different manufacturing steps along the production line. They will all be delivered, at a regular rate, by mid-2017. Throughout the process F4E has managed the technical and organisational interfaces to ensure that all the coils and all their supporting structures fit together and work together – a task that has required extensive involvement in the detailed design and quality assurance implemented by the different contributors.

Following delivery at the Cold Test Facility at CEA Saclay, the first TF coil will now be tested at its nominal operating conditions (25.7kA, 4.5K) as well as being subject to a temperature-induced quench. Of course its thermal and hydraulic characteristics (the coil is cooled by a total flow of approximately 50 g/s helium) will also be confirmed. It will then will be assembled with its Outer Intercoil Structures, re-packed and transported to the JT-60SA site in Naka, Japan.