Rotational Resonance of Nonaxisymmetric Magnetic Braking in the KSTAR Tokamak

Park, J.-K.; Jeon, Y.M.; Ménard, J.; Ko, W. H.; Lee, S. G.; Bae, Y.S.; Joung, M.; You, K.-I.; Lee, K.-D.; Logan, N. C.; Kim, K.; Ko, Jinseok; Yoon, S.W.; Hahn, S.H.; Kim, Junghee; Kim, W. C.; Oh, Y.K.; Kwak, J.G.

doi:10.1103/physrevlett.111.095002

Cited by 41 publications

(28 citation statements)

References 30 publications

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“…With a high E × B, figure 3(c), both calculations show strong enhancement of NTV by bounce-harmonic resonances [21] and observed in experiments [27]. As discussed in references, the perpendicular motion by E × B precession can largely suppress radial particle drifts by phase-mixing, but the phasemixing can disappear in bounce-harmonic resonances as the E × B precession is large enough to resonate with the parallel motion [21].…”

Section: Collisionality Dependency Of Ntv With Finite E × Bsupporting

confidence: 51%

Calculation of neoclassical toroidal viscosity with a particle simulation in the tokamak magnetic braking experiments

et al. 2014

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Accurate calculation of perturbed distribution function δf and perturbed magnetic field δB is essential to achieve prediction of non-ambipolar transport and neoclassical toroidal viscosity (NTV) in perturbed tokamaks. This paper reports a study of the NTV with a δf particle code (POCA) and improved understanding of magnetic braking in tokamak experiments. POCA calculates the NTV by computing δf with guiding-center orbit motion and using δB from the ideal perturbed equilibrium code (IPEC). POCA simulations are compared with experimental estimations for NTV, which are measured from angular momentum balance (DIII-D) and toroidal rotational damping rate (NSTX). The calculation shows good agreement in total NTV torque for the DIII-D discharge, where an analytic neoclassical theory also gives a consistent result thanks to relatively large aspect-ratio and slow toroidal rotations. In NSTX discharges, where the aspect-ratio is small and the rotation is fast, the theory only gives a qualitative guide for predicting NTV. However, the POCA simulation largely improves the quantitative NTV prediction for NSTX. It is discussed that a selfconsistent calculation of δB using general perturbed equilibria is eventually necessary since a non-ideal plasma response can change the perturbed field and thereby the NTV torque.

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Section: Collisionality Dependency Of Ntv With Finite E × Bsupporting

confidence: 51%

Calculation of neoclassical toroidal viscosity with a particle simulation in the tokamak magnetic braking experiments

et al. 2014

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“…56) codes, which have been widely used and found to be in good agreement with experiment. [57][58][59][60][61] Although originally developed to couple externally applied 3D fields to the plasma, this suite of codes is used with an equivalent approach to MISK and PEST for this benchmark. The fluid dW is calculated using the marginally stable eigenfunction from DCON, which is used in IPEC to calculate the 3D perturbed equilibrium.…”

Section: Pentmentioning

confidence: 99%

Benchmarking kinetic calculations of resistive wall mode stability

et al. 2014

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Validating the calculations of kinetic resistive wall mode (RWM) stability is important for confidently predicting RWM stable operating regions in ITER and other high performance tokamaks for disruption avoidance. Benchmarking the calculations of the Magnetohydrodynamic Resistive Spectrum-Kinetic (MARS-K) [Y. Liu et al., Phys. Plasmas 15, 112503 (2008)], Modification to Ideal Stability by Kinetic effects (MISK) [B. Hu et al., Phys. Plasmas 12, 057301 (2005)], and Perturbed Equilibrium Nonambipolar Transport (PENT) [N. Logan et al., Phys.Plasmas 20, 122507 (2013)] codes for two Solov'ev analytical equilibria and a projected ITER equilibrium has demonstrated good agreement between the codes. The important particle frequencies, the frequency resonance energy integral in which they are used, the marginally stable eigenfunctions, perturbed Lagrangians, and fluid growth rates are all generally consistent between the codes. The most important kinetic effect at low rotation is the resonance between the mode rotation and the trapped thermal particle's precession drift, and MARS-K, MISK, and PENT show good agreement in this term. The different ways the rational surface contribution was treated historically in the codes is identified as a source of disagreement in the bounce and transit resonance terms at higher plasma rotation. Calculations from all of the codes support the present understanding that RWM stability can be increased by kinetic effects at low rotation through precession drift resonance and at high rotation by bounce and transit resonances, while intermediate rotation can remain susceptible to instability. The applicability of benchmarked kinetic stability calculations to experimental results is demonstrated by the prediction of MISK calculations of near marginal growth rates for experimental marginal stability points from the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)]. V C 2014 AIP Publishing LLC. [http://dx.

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“…In the present work ν = 10 kin m 2 s −1 is used, so a difference by a factor of two is within the uncertainty. Neglecting in the present modeling the bounce-harmonic resonance effects [24,36] might be a possible source for the discrepancy. Moreover, despite the radial displacement due to the stochasticity which is ≈5-10 times smaller than the banana orbit width, we cannot completely rule out the possibility that effects related to stochasticity may affect the modeled T NTV .…”

Section: Braking Due To Non-resonant Magnetic Perturbations and Compa...mentioning

confidence: 86%

“…In JET, good qualitative agreements have been obtained between T brak and T NTV , while the quantitative results depend on the plasma response [3,23]. In KSTAR, the bounce-harmonic resonance has been experimentally observed and modeled [24].…”

Section: Braking Due To Non-resonant Magnetic Perturbations and Compa...mentioning

confidence: 88%

Braking due to non-resonant magnetic perturbations and comparison with neoclassical toroidal viscosity torque in EXTRAP T2R

et al. 2015

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The non-resonant magnetic perturbation (MP) braking is studied in the EXTRAP T2R reversed-field pinch (RFP) and the experimental braking torque is compared with the torque expected by the neoclassical toroidal viscosity (NTV) theory. The EXTRAP T2R active coils can apply magnetic perturbations with a single harmonic, either resonant or non-resonant. The non-resonant MP produces velocity braking with an experimental torque that affects a large part of the core region. The experimental torque is clearly related to the plasma displacement, consistent with a quadratic dependence as expected by the NTV theory. The work show a good qualitative agreement between the experimental torque in a RFP machine and NTV torque concerning both the torque density radial profile and the dependence on the non-resonant MP harmonic.

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Rotational Resonance of Nonaxisymmetric Magnetic Braking in the KSTAR Tokamak

Cited by 41 publications

References 30 publications

Calculation of neoclassical toroidal viscosity with a particle simulation in the tokamak magnetic braking experiments

Calculation of neoclassical toroidal viscosity with a particle simulation in the tokamak magnetic braking experiments

Benchmarking kinetic calculations of resistive wall mode stability

Braking due to non-resonant magnetic perturbations and comparison with neoclassical toroidal viscosity torque in EXTRAP T2R

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