Measurement of the edge ion temperature in W7-X with island divertor by a retarding field analyzer probe. (17th September 2019)

• Record Type: Journal Article
• Authors: Li, Y.; Henkel, M.; Liang, Y.; Knieps, A.; Drews, P.; Killer, C.; Nicolai, D.; Cosfeld, J.; Geiger, J.; Feng, Y.; Effenberg, F.; Zhang, D.; Hacker, P.; Höschen, D.; Satheeswaran, G.; Liu, S.; Grulke, O.; Jakubowski, M.; Brezinsek, S.; Otte, M.; Neubauer, O.; Schweer, B.; Xu, G.S.; Cai, J.; Huang, Z.
• Other Names: collab.
• Is Part Of: Nuclear fusion. Volume 59:Number 12(2019:Dec.)
• Publication Date: 2019-09-17
• Subjects: ion temperature -- retarding field analyzer -- W7-X -- island configuration -- multi-purpose-manipulator; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/ab3a79
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: Knowledge of the edge ion temperature ( T i ) is important to understand the edge physics in fusion plasmas. The T i edge profile has been successfully measured at W7-X in an island divertor configuration using a retarding field analyzer probe on a reciprocating manipulator. The experimental observations show that in the standard configuration, an ion temperature shoulder at the plasma boundary has been observed near the location where a sudden change of the magnetic field connection length appears in the scrape-off layer (SOL) region. The value of the T i shoulder was observed to be dependent on the edge island structure modified by the control coils, SOL kinetic power, and electron density. A significant reduction and flattening in the edge ion temperature profile has been also observed during the nitrogen seeding from the upper horizontal divertor port. In addition, the edge ion-to-electron temperature ratio has been calculated, which gradually increases with the major radius and decreases with the normalized ion collisionality. An extended two-point model including upstream ion temperature is introduced to understand the experimental measurement.