Observation and analysis of halo current in EAST
摘要
Plasma in a typically elongated cross-section tokamak(for example, EAST) is inherently unstable against vertical displacement. When plasma loses the vertical position control, it moves downward or upward, leading to disruption, and a large halo current is generated helically in EAST typically in the scrape-off layer. When flowing into the vacuum vessel through in-vessel components, the halo current will give rise to a large J × B force acting on the vessel and the in-vessel components. In EAST VDE experiment, part of the eddy current is measured in halo sensors, due to the large loop voltage.Primary experimental data demonstrate that the halo current first lands on the outer plate and then flows clockwise, and the analysis of the information indicates that the maximum halo current estimated in EAST is about 0.4 times the plasma current and the maximum value of TPF × Ih/IP0is 0.65, furthermore Ih/Ip0and TPF × Ih/Ip0tend to increase with the increase of Ip0. The test of the strong gas injection system shows good success in increasing the radiated power, which may be effective in reducing the halo current.