Response of plasma rotation to resonant magnetic perturbations in J-TEXT tokamak

Abstract

The response of plasma toroidal rotation to the external resonant magnetic perturbations (RMP) has been investigated in Joint Texas Experimental Tokamak (J-TEXT) ohmic heating plasmas. For the J-TEXT’s plasmas without the application of RMP, the core toroidal rotation is in the counter-current direction while the edge rotation is near zero or slightly in the co-current direction. Both static RMP experiments and rotating RMP experiments have been applied to investigate the plasma toroidal rotation. The core toroidal rotation decreases to lower level with static RMP. At the same time, the edge rotation can spin to more than 20 km s−1 in co-current direction. On the other hand, the core plasma rotation can be slowed down or be accelerated with the rotating RMP. When the rotating RMP frequency is higher than mode frequency, the plasma rotation can be accelerated to the rotating RMP frequency. The plasma confinement is improved with high frequency rotating RMP. The plasma rotation is decelerated to the rotating RMP frequency when the rotating RMP frequency is lower than the mode frequency. The plasma confinement also degrades with low frequency rotating RMP.

Plasma flow evolution in response to resonant magnetic perturbation in a tokamak

“…Sec. IV and [22]). Recently, such a nonlinear or quasi-linear model for plasma response and flow evolution has been recently extended to allow the "free-slip" condition, where the island phase equation extending beyond the "no-slip" condition is naturally obtained along with the conventional Rutherford equation for island width growth [19].…”

Study of intrinsic rotation by the Gyrokinetic Electromagnetic Numerical Experiment code in the Joint Texas Experimental Tokamak

“…In this paper, the parameters of the experiment are: B T = 1.8 T, I p = 180 kA, n e = (2∼4) × 10 19 m −3 , the edge safety factor q a = 3.3. The tangential X-ray imaging crystal spectrometer, based on a Pilatus detector with a 500 Hz frame rate, has been upgraded to measure the rotation velocity of helium-like argon (Ar XVII) and electron/ion temperature in the core region in the J-TEXT tokamak (Yan et al 2014(Yan et al , 2018. The maximum temporal resolution is 2 ms and spatial resolution is approximately 1.8 cm in ρ = 0∼0.4 along the vertical direction.…”

Overview of the J-TEXT progress on RMP and disruption physics

“…Recent J-TEXT research has contributed to the understanding of the interaction between RMP and tearing mode instabilities. This part summarizes the main findings, including the locking [26][27][28][29][30][31][32][33][34], suppression [26][27][28][29], excitation [35] of the tearing mode and the corresponding thresholds of RMP.…”

“…The mode locking on J-TEXT has been described in several papers from both experimental and theoretical point of views [26][27][28][29][30][31][32][33][34]. We summarize the mode locking phenomenon by displaying two discharges with different phases of the applied RMPs, as shown in In addition, the application of a RMP field rotating at a few kilohertz could lead to the phase locking between rotating RMP and the TM [32].…”

“…We summarize the mode locking phenomenon by displaying two discharges with different phases of the applied RMPs, as shown in In addition, the application of a RMP field rotating at a few kilohertz could lead to the phase locking between rotating RMP and the TM [32]. The TM could either be accelerated [32] or decelerated [33], if the initial slip frequency s TM RMP -f f f  is negative or positive. Unlike the density decrease for TM locked to static RMP [31], the particle confinement could be improved [34] if TM were accelerated as shown in Figure 4.…”