Influence of toroidal rotation from electron cyclotron resonance heating in KSTAR

Lee, S. G.

doi:10.1063/5.0009306

Cited by 8 publications

(4 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Based on this observation, one can infer that ECH changes the toroidal rotation of ohmic tokamak plasmas in the co-current direction. In fact, this phenomenon has been observed in many previous experiments [7,[39][40][41]. In the plateau regime, equation ( 4) can be rewritten as…”

Section: Resultssupporting

confidence: 62%

Toroidal rotation dynamics in KSTAR ohmic plasmas

Lee¹,

Seol²,

Lee³

2022

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

Toroidal rotation dynamics without any external torque sources in KSTAR Ohmic L-mode discharges is investigated. The KSTAR Ohmic plasmas mostly flow in the counter-current direction and the toroidal rotation velocity increases as the plasma density rises. The measured radial electric field in T-10 Ohmic plasmas is generally negative and its magnitude increases as the density rises [A. V. Melnikov et al., Nucl. Fusion 53, 093019 (2013)]. A theoretical picture is introduced in this study to explain how the radial electric field and the toroidal rotation change with the same tendency. The radial electric field can be built up to satisfy the ambipolarity condition and ultimately rotate the plasmas in the toroidal direction.

show abstract

Section: Resultssupporting

confidence: 62%

Toroidal rotation dynamics in KSTAR ohmic plasmas

Lee¹,

Seol²,

Lee³

2022

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, only one ECH source of ∼0.6 MW power is utilized since this power level is optimal for achieving robust ELM crash suppression, considering the ECH effect on the plasma rotation. The ECH injection can change the toroidal rotation profile [50,51]; in the co-I p NBI heated discharges of KSTAR, ECH reduces the co-I p plasma rotation [51]. When the ECH lowers the rotation below the threshold, the ECHinduced rotation drop terminates the suppression phase, as in the DIII-D experiments in which the NBI mix controls the torque affecting the plasma rotation [9].…”

Section: Experimental Conditions Favorable To β N > 24 Elm Crash Supp...mentioning

confidence: 99%

Integrated RMP-based ELM-crash-control process for plasma performance enhancement during ELM crash suppression in KSTAR

et al. 2023

View full text Add to dashboard Cite

The integrated resonant magnetic perturbation (RMP)-based ELM-crash-control process aims to enhance the plasma performance during the RMP-driven ELM crash suppression, where the RMP induces an unwanted confinement degradation. In this study, the normalized beta (βN) is introduced as a metric for plasma performance. The integrated process incorporates the latest achievements in the RMP technique to enhance βN efficiently. The integrated process triggers the n = 1 edge-localized RMP (ERMP) at the L-H transition timing using the real-time machine learning (ML) classifier. The pre-emptive RMP onset can reduce the required external heating power for achieving the same βN by over 10 % compared to the conventional RMP onset. During the RMP phase, the adaptive feedback RMP ELM controller, demonstrating its performance in previous experiments, plays a crucial role in maximizing βN during the suppression phase and sustaining the βN-enhanced suppression state by optimizing the RMP strength. The integrated process achieves βN up to ~2.65 during the suppression phase, which is ~10 % higher than the previous KSTAR record but ~6 % lower than the target of the K-DEMO first phase (βN = 2.8), and maintains the suppression phase above the lower limit of target βN (= 2.4) for ~4 s (~60 τE). In addition to βN enhancement, the integrated process demonstrates quicker restoration of the suppression phase and recovery of βN compared to the adaptive control with the n = 1 conventional RMP (CRMP). The post-analysis of the experiment shows the localized effect of the ERMP spectrum in radial and the close relationship between the evolution of βN and the electron temperature.

show abstract

“…EAST has similarly not found a limit with P ECH , and considering wave heating from lower hybrid and ion cyclotron heating, has accessed RMP-ELM suppression in fully wave-heated discharges [42]. Experiments at KSTAR are ongoing with findings still to be reported [100]. Considering the pedestal impact of P ECH , figure 5(b) shows a high proportion of the data exists at relatively high ion temperature (T i ) as compared to T e , again indicating a preponderance of data with strong ion heating and potentially also significant main ion fuel dilution.…”

Section: Limits To Electron Heatingmentioning

confidence: 97%

Plasma performance and operational space with an RMP-ELM suppressed edge

Paz-Soldan,

Gu,

Leuthold

et al. 2024

Nucl. Fusion

View full text Add to dashboard Cite

The operational space and global performance of plasmas with edge-localized modes (ELMs) suppressed by resonant magnetic perturbations (RMPs) are surveyed by comparing AUG, DIII-D, EAST, and KSTAR stationary operating points. RMP-ELM suppression is achieved over a range of plasma currents, toroidal fields, and RMP toroidal mode numbers. Consistent operational windows in edge safety factor are found across devices, while windows in plasma shaping parameters are distinct. Accessed pedestal parameters reveal a quantitatively similar pedestal-top density limit for RMP-ELM suppression in all devices of just over 3x10^{19} m^{-3}. This is surprising given the wide variance of many engineering parameters and edge collisionalities, and poses a challenge to extrapolation of the regime. Wide ranges in input power, confinement time, and stored energy are observed, with the achieved triple product found to scale like the product of current, field, and radius. Observed energy confinement scaling with engineering parameters for RMP-ELM suppressed plasmas are presented and compared with expectations from established H and L-mode scalings, including treatment of uncertainty analysis. Different scaling exponents for individual engineering parameters are found as compared to the established scalings. However, extrapolation to next-step tokamaks ITER and SPARC find overall consistency within uncertainties with the established scalings, finding no obvious performance penalty when extrapolating from the assembled multi-device RMP-ELM suppressed database. Overall this work identifies common physics for RMP-ELM suppression and highlights the need to pursue this no-ELM regime at higher magnetic field and different plasma physical size.

show abstract

Influence of toroidal rotation from electron cyclotron resonance heating in KSTAR

Cited by 8 publications

References 20 publications

Toroidal rotation dynamics in KSTAR ohmic plasmas

Toroidal rotation dynamics in KSTAR ohmic plasmas

Integrated RMP-based ELM-crash-control process for plasma performance enhancement during ELM crash suppression in KSTAR

Plasma performance and operational space with an RMP-ELM suppressed edge

Contact Info

Product

Resources

About