Speaker
Description
The density limit is a mysterious barrier to magnetic confinement nuclear fusion, hitherto, and is still an unresolved issue. In this report, we will present the recent experimental results of the density limit and core-localized kinetic MHD instabilities on HL-2A. Firstly, the high density discharges with $ne/ne_G>1$ has been achieved by the conventional gas-puff fuelling method in Ohmically heated plasmas, and the corresponding duration time is close to $t\sim500$ $ms$ $\sim$ $30\tau_E$, where $\tau_E$ is the global energy confinement time. Secondly, it is found for the first time that there are multiple MHD instabilities in the core plasmas while $ne/ne_G\sim1$. The analysis suggests that the core localized MHD activities belong to Alfv{\'e}nic ion temperature gradient (AITG) modes or kinetic ballooning modes (KBMs), and firstly it is found on experiment that they trigger the minor or major disruption of bulk plasmas while the density is peaked. These new findings are of great importance to figure out and understand the origin of the density limit.
