Observation of modified divertor particle flux with coherent modes in KSTAR edge plasma

• Published in: Plasma physics and controlled fusion 2019-02, Vol.61 (2), p.25017
• Main Authors: Thatipamula, Shekar G, Kim, H S, Bak, J G, Hong, S H, Nam, Y U
• Format: Article
• Language: English
• Subjects: divertor particle flux; inter-ELM crash, edge coherent mode; poloidal elongation; toroidal rotation velocity
• ISSN: 0741-3335; 1361-6587
• DOI: 10.1088/1361-6587/aaf2a5

The coherent modes in the edge plasma density of KSTAR high confinement mode plasma are found to affect the particle flux incident on the divertor. These coherent modes are synonymous with inter-edge-localized filamentary modes. The coherent structures that typically fall inside the fast toroidal rotation zone or toroidal rotation shear zone, undergo distortion and elongation followed by either breakage or significant modulation in the scrape-off layer (SOL) transport, possibly leading to the observed coherent fluctuations on the divertor slightly further (outward) from the outer strike point. The distorted coherent structures appear as spatially large sized in the poloidal plane and exhibit long range correlation in the edge plasma, extending into the scrape-off layer in some cases. Further, the elongated structures possibly modify the particle flux at the plasma boundary after their onset, and lead to reduced particle flux close to the outer strike point. The coherent modes that occur with relatively smaller spatial size in the edge plasma density at the foot of the toroidal rotation zone do not show any noticeable modification in the particle flux on the divertor. The growth of coherent structures to a large spatial size and distortion is a possible consequence of the presence of strong toroidal flow or flow shear in the location of coherent modes and/or nonlinear evolution.