Healing of the edge magnetic island in the island divertor configuration on J-TEXT

TL;DR

This study demonstrates that high-power electron cyclotron resonance heating (ECRH) can significantly reduce edge magnetic islands in the J-TEXT tokamak, enabling transition from island divertor to limiter configuration, with implications for stable tokamak operation.

Contribution

It introduces a model explaining how ECRH influences the scrape-off layer to heal magnetic islands, advancing understanding of magnetic topology control in tokamaks.

Findings

ECRH reduces the size of edge magnetic islands.

Transition from island divertor to limiter configuration observed.

ECRH power and deposition location are critical for island healing.

Abstract

The phenomena of island healing and configuration transition induced by high-power electron cyclotron resonance heating (ECRH) have been investigated in the island divertor configuration on the J-TEXT tokamak. Experimental results reveal that the size of the edge open magnetic island with mode number m/n = 3/1 decreases substantially under specific ECRH conditions. This process, referred to as island healing, occurs when ECRH with a power of 500~600 kW is deposited in the plasma core or when 250 kW of ECRH is deposited at r = 0.5 a, where a is the minor radius. The reduction of the island width makes the island divertor ineffective and transition into the limiter configuration. A model incorporating the influence of ECRH on the scrape-off layer (SOL) thermoelectric current is proposed to explain the observed changes in the edge magnetic topology of the island divertor configuration. These findings suggest that ECRH should be deposited at the plasma core with carefully controlled power to ensure the stable and compatible operation of ECRH and the island divertor configuration in tokamaks. The results can provide insights into achieving robust operation of an island divertor in tokamaks.