Thermographic studies of outer target heat fluxes on KSTAR

Self Cite

Fully suppressing edge-localized modes (ELMs), e.g., with resonant magnetic perturbations (RMPs), is essential to reach and sustain high-performance steady-state H-mode plasmas because large ELMs can significantly reduce the lifetime of divertor components in future tokamak reactors. RMP-driven ELM suppression in KSTAR has been modeled by coupling the neoclassical transport code PENTRC to the nonlinear 3D MHD code JOREK. We have found that the radial transport from the combined effects of the kink-peeling, tearing response, and neoclassical toroidal viscosity (NTV) can explain the pedestal degradation observed in experiments. In addition, it has been found that the RMP response can increase the inter-ELM heat flux on the lower outer divertor by redistributing the heat transport between the divertor plates. In addition to the degraded pedestal, ELM suppression is also attributable to the RMP-induced mode interactions. While the linear stability of peeling-ballooning mode (PBMs) improves owing to the degraded pedestal, the PBM and RMP interaction increases the spectral transfer between edge harmonics, preventing catastrophic growth and the crash of unstable modes. Here, it turns out that the magnetic islands near the pedestal top can play a vital role in mediating the mode interactions.

Section: Divertor Heat Fluxsupporting

confidence: 84%

Nonlinear MHD modeling of n = 1 RMP-induced pedestal transport and mode coupling effects on ELM suppression in KSTAR

Kim¹,

Pamela²,

Logan³

et al. 2022

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“…The width of B2.5 meshes is 15 mm at the outer midplane, which is wide enough to cover the heat decay length 4-5 mm obtained from simulations. This decay length is comparable to the value typically measured in KSTAR experiments (references [32,33]). We used the same mesh width for SAS and the original open divertors.…”

Section: Settings Of Simulationssupporting

confidence: 85%

“…Generally volumetric loss processes which are important in reducing the heat flux to the target (i.e., via detachment), are directly affected by the divertor structure and wall materials as shown in the case of SAS in DIII-D. In this paper, through numerical simulations using the SOLPS-ITER package [27][28][29][30][31] (but without particle drifts), we examined SASlike divertors in the KSTAR tokamak geometry to identify the factors that dominate the volumetric heat loss near the target (see reference [32,33] for general characteristics of KSTAR). Due to the limited space around the divertor in KSTAR, the depth of the slot used in our study is much smaller than the original SAS in DIII-D (hence, named SAS-like).…”

Section: Introductionmentioning

confidence: 99%

Effects of a shallow SAS divertor on detachment in KSTAR

Kwon

Casali

et al. 2020

For long pulse operation of fusion reactors, it is important to reduce sputter-erosion and power loading of the divertor target by means of plasma detachment. It has been reported that the small-angle-slot (SAS) divertor employed by the DIII-D tokamak can initiate detachment at a relatively low upstream plasma density as it can effectively dissipate heat by concentrating neutrals near the target. Motivated by these findings in DIII-D, we investigated the effects of a SAS-like divertor in KSTAR using SOLPS-ITER simulations without drifts. One remarkable feature revealed by our simulation study is that even a very shallow SAS can lead to a considerably lower heat load on the divertor target than the original flat, open divertor of KSTAR. Deuterium neutrals are concentrated along the divertor separatrix line in the shallow SAS, while deuterium density in the open divertor peaks in the far-scrape-off layer. Furthermore it was found that the neutral density and temperature-drop induced by SAS are both fairly incentive to the depth of the slot. The highest heat dissipation was obtained for a SAS depth of 10.3 cm.

“…In KSTAR, 3-row and 4 column in-vessel control coils (IVCCs) are used to apply n = 1 or n = 2 magnetic perturbations with various toroidal phasing and different configurations. Recently improved degree of control of the RMPs coils made possible investigating the dynamics of the divertor heat flux with changing toroidal phase of the RMPs during a single plasma discharge while continuously maintaining the ELM suppression [10]. It was found that distribution of the divertor heat flux becomes three-dimensional with striation patterns closely resembling results of the field line tracing calculation, especially when including plasma response [11].…”

Section: Implications Of Applied 3d Fieldsmentioning

confidence: 99%

Summary of the 3rd IAEA technical meeting on divertor concepts

Barbarino

Leonard

Asakura³

et al. 2020

During the embargo period (the 12 month period from the publication of the Version of Record of this article), the Accepted Manuscript is fully protected by copyright and cannot be reused or reposted elsewhere. As the Version of Record of this article is going to be / has been published on a subscription basis, this Accepted Manuscript is available for reuse under a CC BY-NC-ND 3.0 licence after the 12 month embargo period.