Nonambipolar Transport due to Electrons with 3D Resistive Response in the KSTAR Tokamak

Yang, SeongMoo; Park, J.-K.; Na, Yong-Su; Wang, Z. R.; Ko, W. H.; In, Y.; Lee, J. H.; Lee, K. D.; Kim, SangKyeun

doi:10.1103/physrevlett.123.095001

Cited by 15 publications

(8 citation statements)

References 36 publications

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“…At this high collisional Pfirsch-Schluter regime, the contribution of collisionless particles for non-ambipolar transport becomes small even considering more energetic particles with E ∼ 4T 0 as discussed in reference [42]. Furthermore, with sufficiently high T e /T i , electron NTV can dominate ion NTV and increase the error field threshold by accelerating plasma rotation [42]. The bigger standard deviation of the error field threshold above ne > 3 × 10 19 m −3 can be related to this complex NTV behavior.…”

Section: Non Monotonic Density Dependence Of N = 1 Error Field Thresholdmentioning

confidence: 90%

“…This can be the case with ne > 3 × 10 19 m −3 in KSTAR L-mode discharges, as indicated by figure 5 (b). At this high collisional Pfirsch-Schluter regime, the contribution of collisionless particles for non-ambipolar transport becomes small even considering more energetic particles with E ∼ 4T 0 as discussed in reference [42]. Furthermore, with sufficiently high T e /T i , electron NTV can dominate ion NTV and increase the error field threshold by accelerating plasma rotation [42].…”

Section: Non Monotonic Density Dependence Of N = 1 Error Field Thresholdmentioning

confidence: 96%

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Parametric dependencies of locked mode thresholds in KSTAR L-mode plasmas

Yang¹,

Park²,

Na³

et al. 2021

Nucl. Fusion

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Resonant error fields with toroidal harmonics n = 1 and n = 2 in otherwise axisymmetric tokamak plasmas can drive disruptive locked modes when their strength exceeds a threshold value. This paper presents the sensitivity of error field threshold in global parameters such as line-averaged density and toroidal magnetic field as well as toroidal harmonics dependence in KSTAR L-mode plasmas. The error field threshold for mode-locking increases along with density up to a roll-over density, which coincides well with the linear ohmic confinement (LOC) to saturated ohmic confinement (SOC) density for the studied KSTAR plasmas. This non-monotonic density correlation of the error field threshold in LOC–SOC can be explained by a modification of existing theoretical scaling in SOC, while plasma rotation can also play an important role in setting the resonant error field threshold.

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Section: Non Monotonic Density Dependence Of N = 1 Error Field Thresholdmentioning

confidence: 90%

Section: Non Monotonic Density Dependence Of N = 1 Error Field Thresholdmentioning

confidence: 96%

Parametric dependencies of locked mode thresholds in KSTAR L-mode plasmas

Yang¹,

Park²,

Na³

et al. 2021

Nucl. Fusion

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“…It has also become standard to use such coils to mitigate or suppress edge localized modes (ELMs) in many of the existing tokamaks [16][17][18][19]. Even when not resonant with any of the above phenomena, non-axisymmetric coils have been observed to induce a neoclassical toroidal viscosity (NTV) torque that can either brake or accelerate the plasma and that scales well in large reactor designs [20][21][22][23]. This torque can * Author to whom any correspondence should be addressed.…”

Section: Motivationmentioning

confidence: 99%

Physics basis for design of 3D coils in tokamaks

Logan¹,

Zhu²,

Park³

et al. 2021

Nucl. Fusion

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Recent progress in 3D tokamak modeling is now leveraged to create a conceptual design of new external 3D field coils for the DIII-D tokamak. In this work generalized perturbed equilibrium code is used to determine optimally efficient spectrum for driving total, core, and edge neoclassical toroidal viscosity torque. These fundamental modes of 3D control are shown to have consistent outboard structures across a wide variety of plasma scenarios and machines. Given these target spectra, the currents and 3D geometry of multiple coils can be optimized to increase efficient drive for the physics of interest without undesired secondary effects. Here, this nonlinear optimization is demonstrated using the flexible optimized coils using space-curves code. The optimized coils are individually distorted in space, creating toroidal ‘arrays’ containing a variety of shapes that often wrap around a significant poloidal extent of the machine. Importantly, efficient coupling can be maintained even when enforcing large distances between coils and the plasma during the geometric optimization of coil designs. The physics-driven optimization presented here thus provides a practical path to utilizing coils built on the exterior of the vacuum chamber in future reactors to obtain the powerful 3D field benefits demonstrated on current machines with close, internal coils.

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“…For instance, the resonant field amplification of plasma response, indicating the β limit of ideal kink instability, has been extensively investigated in various experiments [7][8][9][10]. Such responses are often modelled using linear MHD theory [11][12][13][14][15][16], since the magnitude of magnetic perturbation (δB) is often several orders smaller than the equilibrium magnetic field (B). Many previous works [17][18][19] assume one single dominant stable eigenmode in the plasma response.…”

Section: Introductionmentioning

confidence: 99%

Identification of multiple eigenmode growth rates towards real time detection in DIII-D and KSTAR tokamak plasmas

et al. 2021

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The successful application of three-dimensional (3D) magnetohydrodynamic (MHD) spectroscopy enables us to identify the multi-mode eigenvalues in DIII-D and KSTAR tokamak experiments with stable plasmas. The temporal evolution of the multi-modes’ stabilities have been detected. The new method is numerically efficient allowing the real time detection of MHD modes’ stabilities during the discharge. The method performs active detection of the plasma stability by utilizing the upper and lower rows of internal non-axisymmetric coils to apply a wide variety of 3D fields. Multi-mode eigenvalues are extracted using subspace system identification of the plasma response measured by 3D-field magnetic sensors distributed at different poloidal locations. The equivalence of this new method with the one introduced by Wang (2019 Nucl. Fusion 59 024001) has been numerically corroborated. The more robust and efficient calculation developed here will enable real time monitoring of the plasma stability based on the extracted eigenvalues of stable modes.

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Nonambipolar Transport due to Electrons with 3D Resistive Response in the KSTAR Tokamak

Cited by 15 publications

References 36 publications

Parametric dependencies of locked mode thresholds in KSTAR L-mode plasmas

Parametric dependencies of locked mode thresholds in KSTAR L-mode plasmas

Physics basis for design of 3D coils in tokamaks

Identification of multiple eigenmode growth rates towards real time detection in DIII-D and KSTAR tokamak plasmas

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