Simulation of edge-divertor plasma transport for high-performance operation in KSTAR

The edge-divertor plasma transport responding to type-I edge localized modes (ELMs) in a hybrid scenario and a conventional H-mode operation of the KSTAR (Korea Superconducting Tokamak Advanced Research) tokamak is simulated using a newly developed two-dimensional fluid code named 'EPST', which can be used in time-dependent analyses of the edge-private flux-scrape-off layer region. It is verified through a benchmark test with the B2.5 code for a double-null configuration of the KSTAR tokamak. In this simulation, the KSTAR operation modes are distinguished by their beta(N) values and the threshold pedestal heights for ELM triggering. Type-I ELMs are simulated under the ELM triggering condition by an ad hoc method of time-periodic changes in the transport coefficients in the near-separatrix region. As a result of numerical simulation, the overall distributions of plasma properties responding to the ELM bursts appear to be the same in the edge-divertor region regardless of their beta(N). However, the increased ballooning limit in the higher beta(N) case makes the ELM frequency become lower, while it makes the maximum heat flux on the divertor plate higher compared with the lower beta(N) case.