The magnet system of Wendelstein 7-X stellarator in operation

• Published in: Fusion engineering and design Vol. 136; pp. 12 - 16
• Main Authors: Risse, Konrad, Rummel, Thomas, Bosch, Hans-Stephan, Bykov, Victor, Carls, André, Füllenbach, Frank, Mönnich, Thomas, Nagel, Michael, Schneider, Matthias
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.2018; Elsevier Science Ltd
• Subjects: Circuits; Coils; Experiments; Fusion; Magnetic field; Magnetic fields; Magnets; Plasma physics; Power supplies; Shielding; Stellarator; Superconducting magnets; Superconductivity; Superconducting magnets; Stellarator; Fusion; Magnetic field; Magnets
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2017.12.008

•The stellarator fusion experiment W7-X has a superconducting magnet system and two normally conducting copper coil systems.•The superconducting magnet system was commissioned in July 2017 and is now ready for the 2nd plasma operation period.•Experiences from the first operation phase and field configurations for the upcoming plasma operation period are described.•The paper reports more closely about the optimization of the discharge resistors and mechanical sensor data analysis. The Wendelstein 7-X stellarator (W7-X), one of the largest stellarator fusion experiments, will start the second plasma operation phase in August 2017 at the Max Planck Institute for Plasma Physics in Greifswald, Germany. The main objective of the experiment is to prove the reactor relevance of the stellarator design. Recently the inner wall shielding of the plasma vessel was completed in a 12 month break and a first, inertially cooled divertor has been installed. The coming plasma experiments can be executed with increased ECRH heating power up to 9 MW and a plasma pulse length up to 100 s limited by a total energy input of 80 MJ. The W7-X experiment has a superconducting magnet system with 50 non-planar and 20 planar coils grouped in five equal modules and electrically connected in seven circuits with 10 coils each. Seven power supplies provide individual coil currents in the seven circuits. Two normal conductive copper coil systems can be operated in parallel to the superconducting coils. The paper reports about the experiences with the superconducting magnet system during the first plasma operation phase, about the commissioning for the coming second phase and results from mechanical sensor evaluation.