Direct evidence of E × B flow changes at the onset of resonant magnetic perturbation-driven edge-localized mode crash suppression
Abstract
The bifurcation of perpendicular mode velocity near the pedestal top ([ image ]) at the onset of RMP-driven edge-localized mode (ELM)-crash suppression has been directly measured by using an electron cyclotron emission imaging diagnostic on KSTAR. The ELM crashes are suppressed along with a sudden reduction of [ image ], which synchronizes with the transition into and out of the ELM-crash suppression. The change of [ image ] flow appears mainly responsible for the change of [ image ], whose magnitude is the smallest near the normalized flux surface [ image ] during the ELM-crash suppression. The plasma response to the RMP field was most enhanced in the vicinity of [ image ] during the ELM-crash suppression and showed a hysteresis behavior with respect to resonant field strength. With these changes, a strong nonlinear coupling between turbulent eddies was observed in the ELM-crash suppression, which is an important feature of the ELM-crash suppression.
- Publication:
-
Nuclear Fusion
- Pub Date:
- June 2019
- DOI:
- 10.1088/1741-4326/ab167a
- Bibcode:
- 2019NucFu..59f6033L
- Keywords:
-
- RMP;
- ELM suppression;
- turbulence;
- KSTAR;
- ECEI