Abstract
In order to study the distribution and evolution of the transient heat flux on HL-2A during edge-localized-mode (ELM) bursts, the BOUT++ electromagnetic six-field two-fluid model is used to simulate the pedestal collapse under the lower single-null divertor geometry. The equilibrium profiles of HL-2A ELMy H-mode discharge No. 24 953 are adopted as the initial condition in the original case. In this case, linear analysis shows that the resistive ballooning mode (RBM) and drift-Alfven wave are unstable to this equilibrium, and RBM is the dominant instability. The evolutions of the radial heat fluxes at the outer mid-plane and heat fluxes to the inner and outer targets during the ELM event are presented. Six more equilibria are constructed based on the original case to find out the influence of the pedestal profiles on the peak electron heat flux. The results indicate that the heat flux increases with temperature and/or density, and the theoretical analysis and simulation results consistently show that the heat flux q∥e is proportional to ne0,SEPTe0,SEP32.
Highlights
H-mode, first discovered on the ASDEX tokamak in Germany in 1982,1 is the most promising mode for achieving selfsustaining magnetic confinement fusion at present.2,3 Owing to the large amount of free plasma energy in the edge, edge-localizedmodes (ELMs) are usually excited in an H-mode plasma
When considering the Spitzer resistivity, the linear growth rate represented by red circle curve becomes larger than zero, which means that the equilibrium has the resistivity ballooning mode (RBM), and it is commonly found in the simulations on EAST,25 DIIID,31 and C-Mod
The blue star curve stands for the linear growth rate with the full six-field non-ideal physical effects, and the magenta triangle curve stands for the growth rate based on the full six-field model without the drift Alfven wave (DAW) effects
Summary
H-mode, first discovered on the ASDEX tokamak in Germany in 1982,1 is the most promising mode for achieving selfsustaining magnetic confinement fusion at present. Owing to the large amount of free plasma energy in the edge, edge-localizedmodes (ELMs) are usually excited in an H-mode plasma. ELM events have positive effects on the control of impurity density, their rapidly explosive transport of the particle and heat fluxes will erode the divertor and dramatically affect the operation of tokamaks. Scitation.org/journal/adv other hand, the six-field two-fluid turbulence code mainly focuses on fast turbulence dynamics and is specially developed to simulate the nonlinear crash of ELMs, self-consistent turbulence, and transport between ELMs. Under the turbulence module, simulations have obtained encouraging results on edge plasmas for multiple current tokamaks such as EAST, C-Mod, HL-2A,30 and DIII-D31,32 and future tokamaks such as CFETR20,33 and ITER.. ELMs are usually observed in HL-2A H-mode discharges, and the strong heat flux on the divertor induced by ELMs is a serious concern for the operation. We choose a six-field two-fluid model in BOUT++ to study the heat fluxes during the ELM crash event in HL-2A H-mode discharge.
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