Study of H-mode pedestal predictive model on EAST tokamak

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The poloidal width of the filaments induced by the Type-I edge localized mode has power dependence in EAST. The poloidal widths of the filaments observed by the high-speed vacuum ultraviolet (VUV) imaging system are proportional to the heating power and the ELM size. To understand this power dependence, the BOUT++ nonlinear simulations have been performed with the reconstructed equilibriums from the experimental measurements in this paper. The synthetic filament structures from BOUT++ nonlinear simulation match the experimental observations by the VUV imaging system. The BOUT++ nonlinear simulations also reproduce the power dependence of the filament widths and the ELM size. The filament width and the ELM size are inversely proportional to the toroidal mode number. The low-n mode has a broader radial and poloidal structure, which causes the larger filament width and ELM size. In the high input power case, the mode spectrum shifts to low-n, a result of increasing peeling drive. Besides, we found the β_p in a higher input power case leads to a broader pedestal, expanding the radial mode structure of the Peeling-Ballooning mode.

Section: Parameter Of the Pedestalmentioning

confidence: 99%

Study on filament width of type-I ELM in EAST using VUV imaging system and simulation

Ming

Tang²,

Shi³

et al. 2022

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“…It is needed to perform the stability analysis by theoretical simulation studies before high plasma performance experiments are executed on HL-3. There are several codes that can predict the pedestal profiles: EPED [17], EUROPED [18], and REPED [19,20]. In this paper, we use EPED to perform a study on the prediction of super H-modes in HL-3.…”

Section: Operation Space Of Super H-modes In Hl-3mentioning

confidence: 99%

Nonlinear simulations of the peeling-ballooning instability of super H-modes in the HL-3 tokamak

Zhu,

Zhong,

Zou

et al. 2024

As the newly built tokamak in China, HL-3 is going to explore high performance operation scenario such as super H-mode. The energy confinement and core parameters in super H-mode can be much larger than that in normal H-mode. Based on the pedestal simulation code EPED, the operation space of super H-mode is obtained in HL-3. Magnetic shear decreases with increasing triangularity, and then the super H-mode can be achieved. The threshold of triangularity for accessing super H-mode in HL-3 is around 0.4. By using BOUT++, nonlinear simulation study of the pedestal instabilities in super H-mode equilibrium is executed for the first time. As expected, low n peeling mode which can cause much energy loss (17%) from the pedestal region is dominant in super H-mode. Such a big collapse at pedestal region will lead the transition of super H-mode to H-mode. It is crucial to expand the parameter space of the super H-mode or mitigate the ELM size for sustaining the super H-mode operation. E×B velocity shear is found to play an important role for controlling the ELMs in HL-3. On the one hand, small E×B velocity shear leads to large growth rate but small ELM size around peeling boundary. ELM size is closely related with both of growth rate of peeling-ballooning mode and duration time of linear phase. On the other hand, large E×B velocity shear can stabilize the instabilities near ballooning boundary, and then the parameter space of super H-mode will be enlarged.

“…It should be noted that TGYRO would only predict the profiles in the core region (ρ 0.8) instead of the pedestal. For the pedestal region, the EPED1 model was used in the predictive modeling for CFETR but it needs some calibration like that in reference [44] and some theoretical clarification before its application in the theory-based modeling for the high β p scenario on EAST. Therefore, we use the profiles fitted by experimental measurement for the pedestal and thus the present validation is limited to the core plasma.…”

Section: Integrated Modeling Workflow For Core Plasmamentioning

confidence: 99%

Validation of theory-based integrated modeling and new insights for a high-performance steady-state scenario with only RF heating on EAST

Zhai¹,

Chen²,

Xiang³

et al. 2022

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Theory-based integrated modeling is validated against high-performance steady-state core plasmas on EAST in high poloidal beta (β_p) regime with only RF heating. Reasonably good agreement between the modeling results and experimental measurements is obtained not only for the temperature profiles but also for the 11-chord line-integrated densities and Faraday angles for the first time. This validation effort demonstrates that the safety factor profiles can be non-reversed in high β_p experiments on EAST. The inaccessibility for LH waves observed in conventional ray-tracing simulations for some high β_p experiments is effectively mitigated by including the modeling of wave propagation in scrape-off layer. The observed confinement improvement with density increasing (Gong X, Garofalo A M, Huang J, et al. Nuclear Fusion 2019 59 086030) can be attributed to the reduction of turbulent transport by the collisional stabilization on trapped electron modes rather than by the Shafranov shift stabilization effect which was proposed to be the major cause of confinement enhancement in previous literatures. Based on the successful validation and newly gained physical insights, predictive modeling is performed for core plasma with the upgraded capacity of LH wave system in the upcoming few years and it is shown that the high-performance steady-state H-mode scenario on EAST can be extended to the regime with q95 to be ITER relevant.