Characteristics of global energy confinement in KSTAR L- and H-mode plasmas

Kim, H.-S.; Jeon, Y.M.; Na, Y.-S.; Ghim, Young-chul; Ahn, J.-W.; Yoon, S.W.; Bak, J. G.; Bae, Y.S.; Kim, J.S.; Joung, M.; Jeong, J.H.; Hong, Suk–Ho; Kim, K.M.; Suzuki, Takahiro; Kim, W.C.; Kwak, J.G.

doi:10.1088/0029-5515/54/8/083012

Cited by 10 publications

(10 citation statements)

References 19 publications

(24 reference statements)

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“…Since H 89 is based on the database from various devices, we also checked if these discharges show higher confinement over conventional H-mode discharges in the KSTAR database itself. Figure 3(c) shows that they are located in the higher confinement region in terms of the scaling of the KSTAR H-mode discharges [24]. Note that this scaling was obtained using the KSTAR H-mode database including high beta discharges in contrast to τ E,89 , where very few high beta discharges were included in the database while deriving the scaling law [25].…”

Section: Target Operation Window and Definition Of Hybrid Scenario In...mentioning

confidence: 99%

“…(b) H 89 versus internal inductance (l i ). (c) Energy confinement time from the experiment and the KSTAR H-mode scaling law [24]. Data points correspond to the black circles in figure 2.…”

Section: Early Heating Approachmentioning

confidence: 99%

“…Here, the effective charge, Z eff = 2.0 is assumed [38]. Corresponding confinement enhancement factors, H 89 , H 98 and H KSTAR are presented in figure 10(b) where H KSTAR is the global energy confinement enhancement factor based on the KSTAR H-mode database, τ E /τ KSTAR,H−mode [24]. The ad hoc diffusion coefficient of fast ions, D fast determined to fit W fast in NUBEAM is also plotted in figure 10(b).…”

Section: Performance Analysismentioning

confidence: 99%

See 2 more Smart Citations

On hybrid scenarios in KSTAR

Na¹,

Lee²,

Byun³

et al. 2020

Nucl. Fusion

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We report the status of hybrid scenario experiments in Korea Superconducting Tokamak Advanced Research (KSTAR). The hybrid scenario is defined as stationary discharges with β N ⩾ 2.4 and H 89 ⩾ 2.0 at q 95 < 6.5 without or with very mild sawtooth activities in KSTAR. It is being developed towards reactor-relevant conditions. High performance of β N ≲ 3.0, H 89 ≲ 2.4 and G-factor (≡ β N H 89 /q 2 95 ) ≲ 0.46 has been achieved and sustained for ≳ 40τ E at n e /n GW ~0.7 with heating power of ≲5 MW. Some KSTAR hybrid discharges exhibit a unique feature of a slow transition from conventional H-mode to hybrid mode after the third neutral beam injection. The reason for the confinement enhancement is extensively studied in this transition period of a representative discharge exhibiting a common feature of KSTAR hybrid scenarios. 0D performance analysis with magnetohydrodynamic activities, 1D kinetic profile dynamics, power balance analysis, linear gyro-kinetic analysis and edge pedestal stability analysis were conducted. The enhancement is thought to be from both the core and the pedestal. The improvement in the core region of the ion energy channel is observed from the linear gyro-kinetic analysis considering the electromagnetic, the fast ion, the Shafranov shift, ω E×B , and the magnetic shear effect. The electromagnetic finite β stabilisation plays a role in the inner core region at ρ tor ∼ 0.35 together with the fast ion effect. The alpha stabilisation effect is also found at ρ tor ∼ 0.5. ω E×B , which could reduce the linear growth of the ion temperature gradient mode in the outer core region at ρ tor ∼ 0.5 − 0.7 with the highest contribution from the toroidal rotation. Regarding the improvement in the pedestal, Shafranov shift broadens the stability boundary of the pedestal in support of the diamagnetic effect. The pedestal height and width could be reproduced by the EPED model, while a realistic current profile is used to calculate the internal inductance for Shafranov shift. Based on these findings, a comprehensive confinement enhancement mechanism has been proposed by considering the core-edge interplay.

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Section: Target Operation Window and Definition Of Hybrid Scenario In...mentioning

confidence: 99%

“…(b) H 89 versus internal inductance (l i ). (c) Energy confinement time from the experiment and the KSTAR H-mode scaling law [24]. Data points correspond to the black circles in figure 2.…”

Section: Early Heating Approachmentioning

confidence: 99%

Section: Performance Analysismentioning

confidence: 99%

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On hybrid scenarios in KSTAR

Na¹,

Lee²,

Byun³

et al. 2020

Nucl. Fusion

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show abstract

“…As for the heat transport models, the GLF23 model [30,31] and the Weiland model [32] are tested for the anomalous contribution of the heat transport. Between them, the Weiland model, which reproduces the global experimental trend in ASDEX Upgrade [33] and KSTAR [34], is employed in this work. The Angioni-Sauter model [35] and the Galeev-Sagdeev model [36] are employed for the neoclassical contribution of the ion and the electron heat transport, respectively.…”

Section: Integrated Numerical Modelling Of Ntmmentioning

confidence: 99%

Numerical study on neoclassical tearing mode stabilization via minimum seeking method for the island width growth rate

Kim

Yoo

et al. 2015

Nucl. Fusion

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We report that the control of the ‘island width growth rate’, which is defined as dW/dt, is more efficient than that of the ‘island width’ for neoclassical tearing mode stabilization using the minimum seeking method. A concept of the minimum island width growth rate seeking method is newly proposed for the real-time feedback control of the neoclassical tearing mode by using electron cyclotron current drive. To evaluate the performance of the proposed concept, predictive feedback control simulations with an integrated numerical system are performed based on two types of minimum seeking controllers; the first is a finite difference method based controller and the second is a sinusoidal perturbation based controller. The results are compared with the minimum ‘island width’ seeking method. It is revealed that the proposed control concept is less limited in minimum seeking, and more robust and efficient in reducing the misalignment in shorter time scales.

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“…Their performance is very similar in the high heating phase of 5 to 8 s, as represented by β N < 2.6 and H 89 < 2.3. Note that conventional H-modes typically exhibit β N < 2.0 and H 89 ~ 2.0 in KSTAR 43 . Despite their similar performance, the evolutions of the plasma density are very different.…”

Section: Introductionmentioning

confidence: 99%

A sustained high-temperature fusion plasma regime facilitated by fast ions

Han

Park

Sung

et al. 2022

Nature

Self Cite

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We report a discovery of a fusion plasma regime suitable for commercial fusion reactor where the ion temperature was sustained above 100 million degree about 20 s for the rst time. Nuclear fusion as a promising technology for replacing carbon-dependent energy sources has currently many issues to be resolved to enable its large-scale use as a sustainable energy source. State-of-the-art fusion reactors cannot yet achieve the high levels of fusion performance, high temperature, and absence of instabilities required for steady-state operation for a long period of time on the order of hundreds of seconds. This is a pressing challenge within the eld, as the development of methods that would enable such capabilities is essential for the successful construction of commercial fusion reactor. Here, a new plasma con nement regime called fast ion roled enhancement (FIRE) mode is presented. This mode is realized at Korea Superconducting Tokamak Advanced Research (KSTAR) and subsequently characterized to show that it meets most of the requirements for fusion reactor commercialization. Through a comparison to other well-known plasma con nement regimes, the favourable properties of FIRE mode are further elucidated and concluded that the novelty lies in the high fraction of fast ions, which acts to stabilize turbulence and achieve steady-state operation for up to 20 s by self-organization. We propose this mode as a promising path towards commercial fusion reactors.

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Characteristics of global energy confinement in KSTAR L- and H-mode plasmas

Cited by 10 publications

References 19 publications

On hybrid scenarios in KSTAR

On hybrid scenarios in KSTAR

Numerical study on neoclassical tearing mode stabilization via minimum seeking method for the island width growth rate

A sustained high-temperature fusion plasma regime facilitated by fast ions

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