On the J-TEXT tokamak, the dynamics of edge magnetic topology during the opening of the edge magnetic islands induced by the external Resonant Magnetic Perturbation (RMP) are investigated. The edge island chain is pushed outward by increasing plasma toroidal current to intersect the poloidally and toroidally localized divertor plate, forming an open magnetic island in the Scrape-Off Layer (SOL). The location of the strike points on the divertor plate predicted by the HINT code is in agreement with the experimental observations. The influence of the magnetic topology on edge plasma profiles has also been investigated using Langmuir probes. The properties of edge , , and profiles are studied as function of three magnetic structures in -dependence experiments and two magnetic structures in RMP configuration-dependence experiments. Some common features are observed. Inside the edge closed and SOL remnant islands, flat but non-flat and profiles are detected. When transitioning from the edge closed island to the partially open island with remnant island, the local flat profile is shifted outward accompanied by a narrower flattened region. The steep slopes of , and are measured in the SOL regions characterized by a long connection length , and the longer , the steeper slopes. exhibits a negative well inside the remnant island with infinite and in the SOL regions where significantly exceeds than the electron mean free path , but develops a positive value in the SOL regions where is relatively short.
This paper investigates the dynamics of edge magnetic topology during the opening of edge magnetic islands on the J-TEXT tokamak. It shows how increasing plasma current pushes the edge island chain outward, intersecting the divertor plate and forming an open magnetic island in the Scrape-Off Layer (SOL). The study also examines the influence of magnetic topology on edge plasma profiles, observing flat density but non-flat temperature and potential profiles inside the edge closed and SOL remnant islands.