Dynamics between the fishbone instability and nonlocal transient transport in HL-2A NBI plasmas
Abstract
Understanding of nonlocal electron heat transport is of key importance for current magnetic confinement fusion research. Global nonlocal response presents a fundamental challenge to the standard anomalous transport model based on local microinstabilities and turbulence. Here, we present for the first time a new nonlocal phenomenon triggered by the fishbone instability in HL-2A neutral beam injection plasmas. Rapid core heating leads to a simultaneous decrease in temperature at the plasma edge. The effect reveals fast anomalous transport of core heat pulses to the plasma edge, not compatible with diffusive time scales. More importantly, Δ {{T}\text{e}}/< {{T}\text{e}}> variations at different locations are restricted by the intensity of magnetic fluctuations. The Δ {{T}\text{e}}/< {{T}\text{e}}> and {{≤ft(δ {{B}θ}\right)}\text{rms}} form two types of hysteresis loops at two sides of the inversion radius. The ECEIs show that the 2D mode structure of the fishbone is intensive shearing/spiraling during the nonlocal transport. Experimental results suggest that magnetic perturbation, long-range correlation, mesoscale structure and E× B flow play crucial roles in the nonlocal response. The Hurst exponent and auto-correlation coefficient indicate that the nonlocal transport is potentially linked to the self-organized critical (SOC) dynamics. This work will be beneficial for understanding of the plasma dynamics in future fusion reactors.
- Publication:
-
Nuclear Fusion
- Pub Date:
- April 2016
- DOI:
- 10.1088/0029-5515/56/4/044001
- Bibcode:
- 2016NucFu..56d4001C