Versatile controllability of non-axisymmetric magnetic perturbations in KSTAR experiments

Han, Hyunsun; Jeon, Y.M.; Hahn, S.H.; Ahn, H.S.; Bak, J. G.; In, Y.; Kim, J.; Woo, M.H.; Kim, H.S.; Jin, Junyan; Park, B.H.; Yoon, S.W.

doi:10.1016/j.fusengdes.2016.05.003

Cited by 15 publications

(6 citation statements)

References 14 publications

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“…In this experiment (shot number 16822), a toroidal configuration with n = 1 was employed with a poloidal configuration for resonant magnetic perturbations. The resonant magnetic perturbations were achieved by introducing phase differences of Δφ TM = −95 • and Δφ MB = +85 • between the top-middle and middle-bottom rows [30,31].…”

Section: Methodsmentioning

confidence: 99%

Simulation study of fast ion losses associated with the rotating n = 1 resonant magnetic perturbations in KSTAR

Rhee¹,

Kim²,

Kim³

et al. 2022

Nucl. Fusion

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This paper describes a simulation framework for testing the fast ion loss mechanism associated with the experimentally observed beam ion losses when an externally applied toroidally rotating perturbed magnetic field is used to control edge localized modes in the KSTAR tokamak. The simulations reproduce the key qualitative features of neutral beam injection (NBI) ion detection by a fast ion loss detector. The NBI ion losses in the simulation mainly occur for passing particles due to orbit stochastization, which is caused by orbit resonance with the 3D field perturbations. The relative toroidal angle of NBI ion deposition to the orbit island determines the radial path of the particles between confinement or loss. The fast ion loss quantity depends on the toroidal angle rotation of the 3D field with respect to the beam deposition position. The averaged transport of toroidal canonical angular momentum reveals that linear and nonlinear resonance of the NBI ions within the 3D field are the main factors determining fast ion transport and loss.

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Section: Methodsmentioning

confidence: 99%

Simulation study of fast ion losses associated with the rotating n = 1 resonant magnetic perturbations in KSTAR

Rhee¹,

Kim²,

Kim³

et al. 2022

Nucl. Fusion

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“…Hence, any uncertainties involved in ITER in-vessel mid-RMP coils can be directly addressed in KSTAR. Incorporating broadband switching power amplifiers (SPA) capable of up to 5 kA/turn in DC to 1 kHz, various 3D configurations with n = 1 and/or n = 2 fields can be applied in conjunction with three dozens of assorted patch panels in KSTAR [22]. Besides, along with an upgraded magnetic diagnostic (i.e.…”

Section: Resources For Non-axisymmetric Field Study In Kstarmentioning

confidence: 99%

Enhanced understanding of non-axisymmetric intrinsic and controlled field impacts in tokamaks

Park

Jeon

et al. 2017

Nucl. Fusion

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An extensive study of intrinsic and controlled non-axisymmetric field (δB) impacts in KSTAR has enhanced the understanding about non-axisymmetric field physics and its implications, in particular, on resonant magnetic perturbation (RMP) physics and power threshold (Pth) for L–H transition. The n = 1 intrinsic non-axisymmetric field in KSTAR was measured to remain as low as δB/B0 ~ 4 × 10−5 even at high-beta plasmas (βN ~ 2), which corresponds to approximately 20% below the targeted ITER tolerance level. As for the RMP edge-localized-modes (ELM) control, robust n = 1 RMP ELM-crash-suppression has been not only sustained for more than ~90 τE, but also confirmed to be compatible with rotating RMP. An optimal window of radial position of lower X-point (i.e. Rx = m) proved to be quite critical to reach full n = 1 RMP-driven ELM-crash-suppression, while a constraint of the safety factor could be relaxed (q95 = 5 0.25). A more encouraging finding was that even when Rx cannot be positioned in the optimal window, another systematic scan in the vicinity of the previously optimal Rx allows for a new optimal window with relatively small variations of plasma parameters. Also, we have addressed the importance of optimal phasing (i.e. toroidal phase difference between adjacent rows) for n = 1 RMP-driven ELM control, consistent with an ideal plasma response modeling which could predict phasing-dependent ELM suppression windows. In support of ITER RMP study, intentionally misaligned RMPs have been found to be quite effective during ELM-mitigation stage in lowering the peaks of divertor heat flux, as well as in broadening the ‘wet’ areas. Besides, a systematic survey of Pth dependence on non-axisymmetric field has revealed the potential limit of the merit of low intrinsic non-axisymmetry. Considering that the ITER RMP coils are composed of 3-rows, just like in KSTAR, further 3D physics study in KSTAR is expected to help us minimize the uncertainties of the ITER RMP coils, as well as establish an optimal 3D configuration for ITER and future reactors.

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“…The KSTAR in-vessel control coil (IVCC) system for RMP consists of three rows of four window-pane-like coils in the toroidal direction, 3,17 of which geometrical configuration is similar to three rows of the ITER in-vessel RMP coils. 18 KSTAR has provided results to understand the physics and effects of RMP-driven ELM-crash suppression based on the high reproducibility of the suppression.…”

Section: Introductionmentioning

confidence: 99%

Pedestal electron collisionality and toroidal rotation during ELM-crash suppression phase under n = 1 RMP in KSTAR

Kim

Lee

et al. 2020

Physics of Plasmas

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Versatile controllability of non-axisymmetric magnetic perturbations in KSTAR experiments

Cited by 15 publications

References 14 publications

Simulation study of fast ion losses associated with the rotating n = 1 resonant magnetic perturbations in KSTAR

Simulation study of fast ion losses associated with the rotating n = 1 resonant magnetic perturbations in KSTAR

Enhanced understanding of non-axisymmetric intrinsic and controlled field impacts in tokamaks

Pedestal electron collisionality and toroidal rotation during ELM-crash suppression phase under n = 1 RMP in KSTAR

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