Speaker
Description
See full abstract here
http://ocs.ciemat.es/EPS2019ABS/pdf/P4.1043.pdf
Single and compound helicity tearing mode (TM) responses to a rotating 3D resonant magnetic perturbation (RMP), in the presence of a static error field (EF), have been observed in the partially penetrated regime [1] of the TM unlocking bifurcation process [2] in DIII-D experiments. This regime has been proposed as a stable window over the 3D frequency dependence on simulations with the non-linear resistive reduced MHD code AEOLUS-IT [3,4]. The single helicity structure is formed when the external 3D field rotates with a frequency slightly higher than a critical value, avoiding full-penetration but reaching to a rational surface where the static EF has already formed a magnetic island. The unique standing wave response characteristic of this regime was observed experimentally in high beta, H-mode, DIII-D discharges when the magnitude of the EF was comparable to the rotating 3D field, in qualitative agreement with AEOLUS-IT simulations [1,4]. A similar structure was reported also in ohmic plasmas in J-TEXT [5]. The single helicity perturbation seems resilient to perturbations due to small ELMs.. When sufficiently perturbed, however, the response spreads over neighboring rational surfaces through the poloidal coupling inherent to shaped tokamak plasmas. This results in the formation of a compound (double) helicity state. This helicity deterioration will be compared with new simulations including double resonant surfaces at q=2 and 3.
This work was supported in part by the US Department of Energy under DE-AC02-09CH11466, DE-FC02-04ER54698, DE-AC0506OR23100 and DE-FG02-04ER54761. Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. [1] Okabayashi, M., et al., 2018 IAEA Fusion Energy Conf., EX/P6-25, [2] Fitzpatrick, R., Nucl. Fusion 33 1049 (1993), [3] Inoue, S., al., Plasma. Phy. Control. Fusion 60 025003 (2018), [4] Inoue,S., et all, 2018 IAEA Fusion Energy Conf. TH/P5-24, [5] Wang H, et al 2018 Nucl. Fusion in press
