A large-scale database of two-dimensional UEDGE simulations has been developed to study detachment physics in KSTAR and to support surrogate models for control applications. Nearly 70 000 steady-state solutions were generated, systematically scanning upstream density, input power, plasma current, impurity fraction, and anomalous transport coefficients, with magnetic and electric drifts across the magnetic field included. The database identifies robust detachment indicators, with strike-point electron temperature at detachment onset consistently Te,target similar to 3-4 eV, largely insensitive to upstream conditions. Scaling relations reveal weaker impurity sensitivity than one-dimensional models and show that heat flux widths follow Eich's scaling only for uniform, low D and chi. Distinctive in-out divertor asymmetries are observed in KSTAR, differing qualitatively from DIII-D. Complementary time-dependent simulations quantify plasma response to gas puffing, with delays of 5-15 ms at the outer strike point and similar to 40 ms for the low-magnetic-field-side radiation front. These dynamics are well captured by first-order-plus-dead-time models and are consistent with experimentally observed detachment-control behavior in KSTAR (Gupta et al 2025 Plasma Phys. Control. Fusion (submitted)).

This study delves into the phenomena of fluctuation within the Scrape-Off Layer (SOL) of tokamak fusion reactors, with a specific focus on its impact on SOL width, particularly during grassy Edge Localized Modes (ELMs). Employing a comprehensive approach involving analysis and simulations, including BOUT++ and UEDGE simulations, we examine the role played by the fluctuation energy flux (Γε) and various control parameters in shaping the dynamics of fluctuation entrainment. Our findings shed light on the intricate process of transporting fluctuation energy from the pedestal to the SOL, a process influenced by critical factors such as fluctuation correlation length and SOL electric field shear. These insights yield valuable strategies for effectively managing SOL width and achieving plasma detachment, both of which are essential for optimizing fusion reactor performance and ensuring operational stability. Notably, the adoption of H-mode with small/grassy ELMs holds significant promise in addressing three pivotal challenges for future tokamak fusion reactors: minimizing the size of ELMs, expanding the SOL width, and aiding in the detachment of divertor plasma at lower plasma densities, all while avoiding back transitions to low confinement and disruptions.

Mitigation of large edge-localized modes (ELMs) has been achieved by actively reducing the pedestal density gradient with the EAST new right-angled lower divertor through changing the strike point position from the vertical target to the horizontal target. A series of dedicated experiments in the 2021–2024 EAST campaigns demonstrate that this ELM control solution is highly reproducible in a broad parameter space of edge safety factor q95 = 4.7–7.1, heating power Ptotal = 2.3–5 MW, and pedestal collisionality νe,ped* = 1–6, under both favorable and unfavorable magnetic configurations. Higher plasma density could facilitate the achievement of this ELM control solution. Statistical results indicate that the ELM mitigation effect can be observed at relatively larger Greenwald density fraction of fGW > 0.47. In addition, this ELM mitigation effect can be achieved with both lithium-coated and boronized metal walls. The pedestal density gradient is systematically lower in the horizontal target case than that of the vertical target case when the ELM mitigation effect can be observed. SOLPS-ITER simulation results indicate that the pedestal fueling from divertor recycling is significantly lower in the horizontal target case. This could contribute to the formation of a flattened pedestal density profile with small ELMs.

KSTAR has recently undergone an upgrade to use a new Tungsten divertor to run experiments in ITER-relevant scenarios. Even with a high melting point of Tungsten, it is important to control the heat flux impinging on tungsten divertor targets to minimize sputtering and contamination of the core plasma. Heat flux on the divertor is often controlled by increasing the detachment of Scrape-Off Layer plasma from the target plates. In this work, we have demonstrated successful detachment control experiments using two different methods. The first method uses attachment fraction as a control variable which is estimated using ion saturation current measurements from embedded Langmuir probes in the divertor. The second method uses a novel machine-learning-based surrogate model of 2D UEDGE simulation database, DivControlNN. We demonstrated running inference operation of DivControlNN in realtime to estimate heat flux at the divertor and use it to feedback impurity gas to control the detachment level. We present interesting insights from these experiments including a systematic approach to tuning controllers and discuss future improvements in the control infrastructure and control variables for future burning plasma experiments.

The inherent complexity of boundary plasma, characterized by multi-scale and multi-physics challenges, has historically restricted high-fidelity simulations to scientific research due to their intensive computational demands. Consequently, routine applications such as discharge control and scenario development have relied on faster but less accurate empirical methods. This work introduces DivControlNN, a novel machine-learning-based surrogate model designed to address these limitations by enabling quasi-real-time predictions (i.e., ∼0.2 ms) of boundary and divertor plasma behavior. Trained on over 70,000 2D UEDGE simulations from KSTAR tokamak equilibria, DivControlNN employs latent space mapping to efficiently represent complex divertor plasma states, achieving a computational speed-up of over 108 compared to traditional simulations while maintaining a relative error below 20% for key plasma property predictions. During the 2024 KSTAR experimental campaign, a prototype detachment control system powered by DivControlNN successfully demonstrated detachment control on its first attempt, even for a new tungsten divertor configuration and without any fine-tuning. These results highlight the transformative potential of DivControlNN in overcoming diagnostic challenges in future fusion reactors by providing fast, robust, and reliable predictions for advanced integrated control systems.

The low-edge rotation, intrinsically ELM-free, and improved confinement wide-pedestal quiescent H-mode (QH-mode), discovered in DIII-D tokamak, has pedestal widths exceeding the EPED-kinetic-ballooning mode (KBM) model scaling typically by at least 25%. Ion-scale ( k(y)rho(s) < 1) microturbulence and its role in setting the pedestal structure is investigated using the radially local delta f gyrokinetic code CGYRO. The electromagnetic trapped electron mode (TEM) is unstable at the pedestal top, while plasma beta ( beta(e) ) is similar to 60% below the KBM onset threshold and the electron temperature gradient mode is found to be unstable in the peak gradient region. Nonlinear simulation reveals that the ion-scale turbulence could produce electron energy flux consistent with the flux inferred from power balance at the pedestal top, with a reasonable variation of the local E x B shearing rate; and the local neoclassical transport from NEO is dominant over the simulated turbulent transport in the ion energy flux channel. The simulated ion-scale turbulence produces much lower electron energy flux than inferred from experiment in the pedestal peak gradient region. A correction to the EPED-KBM pedestal width scaling is obtained based on the two-dimensional scan of pedestal top plasma beta ( beta(e) ) and normalized electron density and temperature scale lengths, a/Ln(e), a/LTe using CGYRO linear simulations. Mode transitions among TEM, micro-tearing mode, ion-temperature gradient mode and KBM, are observed in the 2D scan at the pedestal top. A fixed normalized growth rate for these drift-type modes is taken to determine the pedestal width scaling, which shows good consistency with the QH experimental database on pedestal heights and widths. The onset of KBM instabilities and the local E x B shear suppression criterion set the lower and upper limit for the pedestal width of standard QH-mode, wide-pedestal QH-mode and type-I ELMy H mode. A potentially higher and wider pedestal is expected from the new scaling of pedestal width. This work presents an improved understanding of the ion-scale micro-turbulence of wide-pedestal QH-mode and sheds light on a promising scenario for future reactors, including ITER and beyond.

The international thermonuclear experimental reactor (ITER) is now considering to use tungsten as the material for plasma-facing components (PFCs) [1] and operate in the so-called high-confinement mode (H-mode) [2]. Heat pulse eruptions caused by the plasma instability named the edge localized mode (ELM) pose a critical threat to the PFCs, which can lead to severe material damage and generate metallic impurities that contaminate the core plasma, rendering stable H-mode operation difficult [3]. Therefore, ITER and future fusion reactors are desired to operate in a plasma regime without ELM but with good energy confinement, simultaneously coupled with the plasma detachment to relieve heat load on the material surface [4]. However, such an operational regime has not yet been demonstrated for long pulse without expense of energy confinement, and the mechanism for maintaining ELM suppression in a detached H-mode plasma remains unclear. Here, we report the first demonstration of the achievement of a long-pulse detached H-mode plasma regime without ELM but with energy confinement even better than the standard H-mode in a metal-wall environment, and elucidate, for the first time, the underlying physics. We find that a high-frequency turbulence is excited at the plasma edge that provides a radial transport channel, thus preventing ELM generation. Simulations suggest that in ITER the plasma edge will be more prone to turbulences, as turbulence suppression by the ExB flow shear is expected to be significantly weaker than that in present tokamaks [5]. These findings may lead to a promising operational scenario for future tokamak fusion reactors compatible with metal-wall conditions, which is essential for harvesting fusion energy.

Since the last IAEA-FEC in 2021, significant progress on the development of long pulse steady state scenario and its related key physics and technologies have been achieved, including the reproducible 403 s long-pulse steady-state H-mode plasma with pure radio frequency (RF) power heating. A thousand-second time scale (similar to 1056 s) fully non-inductive plasma with high injected energy up to 1.73 GJ has also been achieved. The EAST operational regime of high beta(P) has been significantly extended (H-98y2 > 1.3, beta(P) similar to 4.0, beta(N) similar to 2.4 and n(e)/n(GW) similar to 1.0) using RF and neutral beam injection (NBI). The full edge localized mode suppression using the n = 4 resonant magnetic perturbations has been achieved in ITER-like standard type-I ELMy H-mode plasmas with q(95) approximate to 3.1 on EAST, extrapolating favorably to the ITER baseline scenario. The sustained large ELM control and stable partial detachment have been achieved with Ne seeding. The underlying physics of plasma-beta effect for error field penetration, where toroidal effect dominates, is disclosed by comparing the results in cylindrical theory and MARS-Q simulation in EAST. Breakdown and plasma initiation at low toroidal electric fields (<0.3 V m(-1)) with EC pre-ionization is developed. A beneficial role on the lower hybrid wave injection to control the tungsten concentration in the NBI discharge is observed for the first time in EAST suggesting a potential way toward steady-state H-mode NBI operation.

The coupling of transport code SOLPS with the turbulence code BOUT++ was reported in Reference [D. R. Zhang et al., Phys. Plasmas 26, 012508 (2019)], while the grids of SOLPS and BOUT++ are not completely consistent with each other, especially in the divertor region. In the present work, a method of replacing the grids of BOUT++ with the grids of SOLPS is proposed to make the simulation region fully consistent with each other for the SOLPS/BOUT++ coupling. A SOLPS grid file is generated with an MHD equilibrium and used in BOUT++ code to simulate the profiles of plasma density, ion temperature, and electron temperature with the six-field two-fluid model. The profiles of the main plasma parameters simulated with the SOLPS grids are similar with the profiles simulated with the BOUT++ grids at the midplane, while the profiles are deformed compared with the profiles simulated with the BOUT++ grids at the outer divertor target because of the differences of the distributions of SOLPS grids and BOUT++ grids in the divertor region. The radial particle transport coefficient and heat transport coefficients are also calculated by using the BOUT++ code with the two grids, and the comparisons of the radial particle transport coefficient and heat transport coefficients simulated with the two grids at the midplane and outer divertor target plate are discussed.

Viable magnetic fusion devices necessitate combining good confinement with effective power flux handling. A major concern for ITER, and devices beyond, is the divertor heat load width, which sets peak boundary heat loads on the plasma-facing materials. Current estimates of the heat flux width are narrow for future reactors. Here, we demonstrate how pedestal turbulence can expand into, or entrain, the stable scrape-off-layer and so broaden the heat flux width beyond these neoclassical predictions. Employing combined theoretical, computational, and experimental approaches, we focus on quiescent high confinement discharges on the DIII-D tokamak, but the results are of broader significance. Our findings uncover common trends in the edge turbulence intensity flux, the pressure perturbation skewness, and the turbulence mixing length, which together determine the heat flux width. This research demonstrates the physics of scrape-off-layer broadening by turbulence and highlights the promise of a turbulent pedestal for successful core-edge integration in ITER and future fusion devices.

肺高压危象是肺动脉高压的严重并发症之一，救治难度大，死亡风险高。以基础疾病控制、右心衰竭综合管理、充分肺高压靶向药物治疗、体外生命支持等为基础的多学科团队协作是肺高压危象救治成功的重要保证，可显著降低患者死亡风险。该文报道多学科团队联合成功救治肺高压危象产妇1例，以期为肺高压危象患者的救治提供经验和参考。.

BOUT++ turbulence simulations were performed to investigate the impact of turbulence spreading on the edge localized mode (ELM) size and divertor heat flux width $({\lambda _q})$ broadening in small ELM regimes. This study is motivated by EAST experiments. BOUT++ linear simulations of a pedestal radial electric field (Er) scan show that the dominant toroidal number mode (n) shifts from high-n to low-n, with a narrow mode spectrum, and the maximum linear growth rate increases as the pedestal Er well deepens. The nonlinear simulations show that as the net E × B pedestal flow increases, the pressure fluctuation level and its inward penetration beyond the top of the pedestal both increase. This leads to a transition from small ELMs to large ELMs. Both inward and outward turbulence spreading are sensitive to the scrape-off-layer (SOL) plasma profiles. The inward turbulence spreading increases for the steep SOL profiles, leading to increasing pedestal energy loss in the small ELM regime. The SOL width $({\lambda _q})$ is significantly broadened progressing from the ELM-free to small ELM regime, due to the onset of strong radial turbulent transport. The extent of the SOL width $({\lambda _q})$ broadening depends strongly on outward turbulence spreading. The fluctuation energy intensity flux ${\varGamma _\varepsilon }$ at the separatrix can be enhanced by increasing either pedestal Er flow shear or local SOL pressure gradient. The ${\lambda _q}$ is broadened as the fluctuation energy intensity flux ${\varGamma _\varepsilon }$ at the last close flux surface (LCFS) increases. Local SOL E × B flow shear will restrain outward turbulence spreading and the associated heat flux width broadening. Operating in H-mode with small ELMs has the potential to solve two critical problems: reducing the ELM size and broadening the SOL width.

This study delves into Microtearing Modes (MTMs) in tokamak plasmas, employing advanced simulations within the BOUT++ framework. The research, centering on collisional MTMs influenced by the time-dependent thermal force, enhances our understanding of plasma dynamics. It achieves this through the simplification and linearization of control equations in detailed linear simulations. The study meticulously evaluates various conductivity models, including those proposed by Larakers, Drake, and Hassam, under diverse plasma conditions and collision regimes. A notable achievement of this research is the derivation of a unified dispersion relation that encompasses both MTM and Drift-Alfven Wave (DAW) instabilities. It interestingly reveals that DAW and MTM exhibit instability at different proximities to the rational surface. Specifically, MTMs become unstable near the rational surface but stabilize farther away, whereas the drift-Alfven instability manifests away from the rational surface. Further, the study re-derives MTM dispersion relations based on Ohm's law and the vorticity equation, providing a thorough analysis of electromagnetic and electrostatic interactions in tokamaks. Global simulations demonstrate an inverse correlation between MTM growth rates and collisionality, and a direct correlation with temperature gradients. The nonalignment of the rational surface with the peak of electron local diamagnetic frequency stabilizes the MTMs. Nonlinear simulations highlight electron temperature relaxation as the primary saturation mechanism for MTMs, with magnetic flutter identified as the dominant mode of electron thermal transport.

Triangularity is an important shaping parameter in tokamak plasmas that affects the edge plasma state. In this work, we utilize the BOUT++ code to study the effect of positive and negative triangularity on the peeling–ballooning modes with H-mode profiles. The model equilibria with a JET-like geometry are self-consistently generated by the CORSICA equilibrium code, with a fixed pressure profile when varying triangularity. The linear simulations reveal that increasing positive triangularity results in the increase in magnetic shear and decrease in radial electric field (Er) curvature, leading to the stabilization of the peeling–ballooning modes. On the contrary, the increase in negative triangularity results in a destabilizing effect due to the decrease in magnetic shear and increase in Er curvature. It is found that the modification of Er shear due to triangularity variation cannot impact edge stability significantly. The nonlinear simulations further demonstrate that more positive triangularity results in reduced nonlinear energy loss fraction or pedestal collapse, while more negative triangularity results in increased nonlinear energy loss fraction or pedestal collapse. These results provide qualitative insights into experimental observations of the high pedestal pressure profiles with positive triangularity configuration and restricted low pedestal pressure profiles with negative triangularity configuration.

We report a two-stage crash process in edge localized mode (ELM) driven by resistive drift-ballooning modes (RDBMs) numerically simulated in a full annular torus domain. In the early nonlinear phase, the first crash is triggered by linearly unstable RDBMs and m/n = 2/1 magnetic islands are nonlinearly excited via nonlinear couplings of RDBMs. Simultaneously, middle-n RDBM turbulence develops but is poloidally localized around X-points of the magnetic islands, leading to the small energy loss. Here m is the poloidal mode number, n is the toroidal mode number, the q = 2 rational surface exists at the pressure gradient peak, and q is the safety factor, respectively. The second crash occurs in the late nonlinear phase. Low-n magnetic islands are also excited around the q = 2 surface via nonlinear couplings among the middle-n turbulence. Since the turbulence develops from the X-points of higher harmonics of m/n = 2/1 magnetic islands, it expands out poloidally. The second crash is triggered when the turbulence covers the whole poloidal region. A scan of toroidal wedge number N, where full torus is divided into N segments in the toroidal direction, also reveals that the first crash process becomes more prominent with the higher toroidal wedge number where the RDBMs play a dominant role. These results indicate that nonlinear interactions of all channels in the full torus domain can significantly affect the trigger dynamics of ELMs driven by the RDBMs.

The edge plasma turbulence and transport dynamics, as well as the divertor power loads during the thermal quench phase of tokamak disruptions are numerically investigated with BOUT++'s flux-driven, six-field electromagnetic turbulence model. Here a transient yet intense particle and energy sources are applied at the pedestal top to mimic the plasma power drive at the edge induced by a core thermal collapse, which flattens core temperature profile. Interesting features such as surging of divertor heat load (up to 50 times), and broadening of heat flux width (up to 4 times) on the outer divertor target plate, are observed in the simulation, in qualitative agreement with experimental observations. The dramatic changes of divertor heat load and width are due to the enhanced plasma turbulence activities inside the separatrix. Two cross-field transport mechanisms, namely the $E\times B$ turbulent convection and the stochastic parallel advection/conduction, are identified to play important roles in this process. Firstly, elevated edge pressure gradient drives instabilities and subsequent turbulence in the entire pedestal region. The enhanced turbulence not only transports particles and energy radially across the separatrix via $E\times B$ convection which causes the initial divertor heat load burst, but also induces an amplified magnetic fluctuation $\tilde{B}$. Once the magnetic fluctuation is large enough to break the magnetic flux surface, magnetic flutter effect provides an additional radial transport channel. In the late stage of our simulation, $|\tilde{B}_r/B_0|$ reaches to $10^{-4}$ level that completely breaks magnetic flux surfaces such that stochastic field-lines are directly connecting pedestal top plasma to the divertor target plates or first wall, further contributing to the divertor heat flux width broadening.

Data-driven science and technology offer transformative tools and methods to science. This review article highlights the latest development and progress in the interdisciplinary field of data-driven plasma science (DDPS), i.e., plasma science whose progress is driven strongly by data and data analyses. Plasma is considered to be the most ubiquitous form of observable matter in the universe. Data associated with plasmas can, therefore, cover extremely large spatial and temporal scales, and often provide essential information for other scientific disciplines. Thanks to the latest technological developments, plasma experiments, observations, and computation now produce a large amount of data that can no longer be analyzed or interpreted manually. This trend now necessitates a highly sophisticated use of high-performance computers for data analyses, making artificial intelligence and machine learning vital components of DDPS. This article contains seven primary sections, in addition to the introduction and summary. Following an overview of fundamental data-driven science, five other sections cover widely studied topics of plasma science and technologies, i.e., basic plasma physics and laboratory experiments, magnetic confinement fusion, inertial confinement fusion and high-energy-density physics, space and astronomical plasmas, and plasma technologies for industrial and other applications. The final Section before the summary discusses plasma-related databases that could significantly contribute to DDPS. Each primary Section starts with a brief introduction to the topic, discusses the state-of-the-art developments in the use of data and/or data-scientific approaches, and presents the summary and outlook. Despite the recent impressive signs of progress, the DDPS is still in its infancy. This article attempts to offer a broad perspective on the development of this field and identify where further innovations are required.

The kinetic peeling-ballooning mode (KPBM) plays a crucial role in the edge turbulence and transport in a tokamak plasma. However, the impact of the bootstrap current on KPBM is still unclear. Simulations of KPBM using the BOUT++ 3 + 1 gyro-Landau-fluid code are presented in this study. To investigate the KPBM in a real tokamak equilibrium, the global equilibrium solver CORSICA was employed to generate a set of realistic equilibria of shifted circular geometry, including the Shafranov shift, elongation effects and bootstrap current. The linear instability property of the KPBM is observed in a wide range of pressure gradient and parallel current density in the pedestal region. Our results indicate that the bootstrap current has a stabilizing effect on the high-n KPBM over the entire pedestal region. Here, n is the toroidal mode number. In comparison with the ideal magnetohydrodynamic peeling-ballooning mode stability diagram, the unstable KPBM region shrinks and shifts to low β P G ( β P G = ( 2 μ 0 p P G ) / ( B 0 2 ) where p P G denotes the pressure at the peak pressure gradient position) with the increase of the bootstrap current. Moreover, we find that the low-n kink modes are driven unstable by the bootstrap current in the second stable region. With an additional external current drive on top of the bootstrap current, the low-n KPBMs can be stabilized when the total edge current is sufficiently large, although the low-n kink mode is still unstable in the β P G region with β P G > 0.45 % .

For tokamak edge plasma simulation, a plasma simulation framework BOUT++ employs a dual coordinate system to simulate moderate- n and high- n plasma instability with reasonable computational cost, where n is the toroidal mode number. This coordinate system however limits the computational domain to the toroidal wedge (full torus divided into N parts in the toroidal direction) for computational efficiency and the use of flute-ordering approximation in the field solver calculating the flow potential from the vorticity which may not be valid for low- n modes. Improving numerical treatment of low- n modes is however indispensable to address simulations of low- n current-driven edge localized mode (ELM), ELM control by resonant magnetic perturbations (RMPs), edge turbulence with RMPs and so on. In this work, BOUT++ is extended to simulate the interplay between n = 0 , low- n and high- n plasma components in a full annular tokamak edge domain through hybrid modeling of the flow potential and the vorticity. Low- n modes of flow potential are calculated in an orthogonal flux surface coordinate and high- n modes in the dual coordinate system separately in Fourier space. The proposed scheme can capture an interplay between n = 1 global modes and high- n turbulence during pedestal collapse in a full annular torus domain with a circular cross section.

Predictions of heat load widths λ q based on particle orbits alone are very pessimistic. This paper shows that pedestal peeling-ballooning (P-B) magnetohydrodynamic (MHD) turbulence broadens the stable scrape-off layer (SOL) by the transport, or spreading, of fluctuation energy from the pedestal. λ q is seen to increase with Γ ε , the fluctuation energy density flux. We elucidate the fundamental physics of the spreading process. Γ ε increases with pressure fluctuation correlation length. P-B turbulence is seen to be especially effective at spreading, on account of its large effective mixing length. Spreading is shown to be a multiscale process, which is enhanced by the synergy of large and small-scale modes. Pressure fluctuation skewness correlates well with the spreading flux–with the zero crossing of skewness and Γ ε spatially coincident–suggesting the role of coherent fluctuation structures and the presence of intermittency in λ q broadening. λ q ∼ B p − 1 scaling persists for the broadened SOL. We show that the spreading flux increases for increasing pedestal pressure gradient ∇ P 0 and for decreasing pedestal collisionality υ ped ∗ . This trend is due to the dominance of peeling modes for large ∇ P 0 and low υ ped ∗ . Ultimately, we see that a state of weak MHD turbulence, as for small ELMs, is very attractive for heat load management. Our findings have transformative implications for future fusion reactor designs and call for experimental investigations to validate the observed trends.