Tearing mode velocity braking due to resonant magnetic perturbations

Frassinetti, L.; Menmuir, S.; Olofsson, Karl; Brunsell, Per R.; Drake, James R.

doi:10.1088/0029-5515/52/10/103014

Cited by 19 publications

(35 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Braking and locking of a tearing mode caused by an RMP has been studied both in tokamaks [13][14][15][22][23][24]27 and a) richard.fridstrom@ee.kth.se RFPs. 25,28 In EXTRAP T2R reversed-field pinch, TM dynamics 25 and velocity braking 29 due to a single-harmonic RMP were found to be in qualitative agreement with theory. 12,19 Furthermore, after TM wall-locking, hysteresis caused by reduction of viscous torque and increase in the tearing mode amplitude has been experimentally observed.…”

Section: Introductionsupporting

confidence: 59%

Tearing mode dynamics and locking in the presence of external magnetic perturbations

et al. 2016

Self Cite

View full text Add to dashboard Cite

In normal operation, Madison Symmetric Torus (MST) [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field pinch plasmas exhibit several rotating tearing modes (TMs). Application of a resonant magnetic perturbation (RMP) results in braking of mode rotation and, if the perturbation amplitude is sufficiently high, in a wall-locked state. The coils that produce the magnetic perturbation in MST give rise to RMPs with several toroidal harmonics. As a result, simultaneous deceleration of all modes is observed. The measured TM dynamics is shown to be in qualitative agreement with a magnetohydrodynamical model of the RMP interaction with the TM [R. Fitzpatrick, Nucl. Fusion 33, 1049 (1993)] adapted to MST. To correctly model the TM dynamics, the electromagnetic torque acting on several TMs is included. Quantitative agreement of the TM slowing-down time was obtained for a kinematic viscosity in the order of νkin≈10–20 m2/s. Analysis of discharges with different plasma densities shows an increase of the locking threshold with increasing density. Modeling results show good agreement with the experimental trend, assuming a density-independent kinematic viscosity. Comparison of the viscosity estimates in this paper to those made previously with other techniques in MST plasmas suggests the possibility that the RMP technique may allow for estimates of the viscosity over a broad range of plasmas in MST and other devices.

show abstract

Section: Introductionsupporting

confidence: 59%

Tearing mode dynamics and locking in the presence of external magnetic perturbations

et al. 2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…For the presented parameters, A = 0.955×10 7 Nm -2 , indicating F em ~ 2.5Nm -2 and F vs ~ 1.8Nm -2 at RS at the first beginning, the magnitude of which are in good agreement with the experimental estimation. 10 Numerical results shown in Figs. 5 to 8 indicate the applied RMP contributes a net stabilizing and braking effect to resistive TM, while it is still unable to identify what is the dominant stabilizing effect for the suppression of TM.…”

Section: Fig 7 Time Evolution Of (A) Normalized Island Width W/a (mentioning

confidence: 99%

“…3 Since the first RMPs experiment on PULSATOR, 4 many experiments related to RMPs have been carried out. 1,[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The RMPs related experiments covers a broad spectrum of physics issues including the effect of RMPs on tearing mode (TM) dynamics, 1, 4-10 error field, 11,12 particle transport, 13,14 and mitigation or suppression of edge localized modes (ELMs). [15][16][17][18] One of the results is that RMPs with moderate amplitude can suppress Mirnov oscillations effectively.…”

Section: Introductionmentioning

confidence: 99%

Understanding the effect of resonant magnetic perturbations on tearing mode dynamics

Ren

et al. 2013

Physics of Plasmas

View full text Add to dashboard Cite

Abstract. Numerical understandings of the effect of resonant magnetic perturbations (RMPs) on 2/1 tearing mode (TM) dynamics observed on J-TEXT tokamak (Hu Q. et al 2012 Nucl. Fusion 52 083011) are presented in this paper. The non-uniform mode rotation frequency, modulated by electromagnetic force (F em ) and viscous force (F vs ), results in the applied RMPs contributing both net stabilizing and braking effect on TM. Numerical evaluation based on analytical theory shows the applied RMP contributes a dominant stabilizing effect, which are responsible for the suppression of TM. The dynamics of the first discovered small locked island (SLI) are investigated. It is found that the island is locked at the stabilizing phase and the saturated island width is less than the linear layer width. The simulated Mirnov signal indicates the small locked island is likely to be the complete suppression case observed in experiments. Associated with the application of RMP, the shape of Mirnov signal deviates from sinusoidal before mode locking, which is explained by numerical modeling. The comparisons between the numerical and experimental results are in good agreement phenomenally.

show abstract

“…Complementing the biasing technique, we utilized braking with the RMP technique [29,47], in which an external m = 1 RMP produces an electromagnetic torque at each TM resonant surface [48]. Injected through a cut in MST's conducting shell, this torque acts to reduce the phase difference between the rotating TMs and the static RMP.…”

mentioning

confidence: 99%

Dependence of Perpendicular Viscosity on Magnetic Fluctuations in a Stochastic Topology

et al. 2018

Self Cite

View full text Add to dashboard Cite

In a magnetically confined plasma with a stochastic magnetic field, the dependence of the perpendicular viscosity on the magnetic fluctuation amplitude is measured for the first time. With a controlled, ∼ tenfold variation in the fluctuation amplitude, the viscosity increases ∼100-fold, exhibiting the same fluctuation-amplitude-squared dependence as the predicted rate of stochastic field line diffusion. The absolute value of the viscosity is well predicted by a model based on momentum transport in a stochastic field, the first in-depth test of this model.

show abstract

Tearing mode velocity braking due to resonant magnetic perturbations

Cited by 19 publications

References 49 publications

Tearing mode dynamics and locking in the presence of external magnetic perturbations

Tearing mode dynamics and locking in the presence of external magnetic perturbations

Understanding the effect of resonant magnetic perturbations on tearing mode dynamics

Dependence of Perpendicular Viscosity on Magnetic Fluctuations in a Stochastic Topology

Contact Info

Product

Resources

About