A newly developed integrated suite of codes coined as tokamak reactor integrated automated suite for simulation and computation (TRIASSIC) is reported. The suite comprises existing plasma simulation codes, including 1.5D/2D plasma transport solvers and neoclassical/anomalous transport, plasma heating/cooling, and cold neutral models. The components in TRIASSIC are fully modularized by adopting a generic data structure as its internal storage. Primary components such as the transport solver and the neutral beam or electron cyclotron wave actuator were verified to its standalone implementation. The interpretive and predictive simulations of 50 stationary plasma phases from 30 KSTAR discharges were conducted for validation, and a good agreement with experimental measurements on all simulation cases was found.

An optimum plasma pressure/current density profile and corresponding heating/current drive (H/CD) determination scheme is newly developed by integrating equilibrium, stability, confinement, and H/CD, self-consistently subject to maximize the fusion gain for Korean fusion demonstration reactor (K-DEMO) steady-state operation scenarios. The integrated plasma modeling package, FASTRAN/IPS, is adopted for the integrated numerical apparatus. The target pressure profile with a pedestal structure is investigated by varying its peaking, pedestal height and width as a first step. Formation of stable equilibria is evaluated by solving the Grad–Shafranov equation and checking linear MHD stability. For the case of potentially stable equilibrium, required external heating distribution is calculated by considering both power balance and external current drive alignment to reproduce the pressure profile of the stable equilibrium. Electron/ion temperature and poloidal flux evolutions are solved with the derived heating configuration to find a steady-state scenario and achieve self-consistent plasma profiles. A self-consistent target steady-state pressure and current profile parameters are proposed through designed systematic algorithm with fusion power PF  =  2070 MW, fusion gain Q  =  19.7, and normalized beta βN  =  2.8 at toroidal field BT  =  7.4 T and plasma current IP  =  15.5 MA. Feasibility of fusion power PF  =  3000 MW operation is also explored with enhanced density and temperature limit assumption.

A fast-ion Dα (FIDA) diagnostics system was installed for core and edge measurements on KSTAR. This system has two tangential FIDA arrays that cover both blue- and redshifted Dα lines (cold: 656.09 nm) in active views along the neutral beam 1 A centerline. The spectral band is 647–662.5 nm, and it covers the Doppler shift of the emission from the maximum energy of the neutral beam (100 keV). A curved filter strip with a motorized stage adequately prevents saturation of the electron multiplying charge-coupled device signal by the cold Dα line from the plasma edge. From comparisons of the measured spectra and FIDASIM modeling code, the FIDA spectra are well matched quantitatively. Moreover, the first measurements show that the FIDA radiance agrees with the neutron rate in the time trace during external heating and perturbation. In addition, responses are observed in the core FIDA radiance during the edge-localized mode cycle.

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Based on an approximate modeling of scrape-off-layer (SOL) dynamics and edge turbulence, it is shown that a new type of limit cycle oscillation (LCO) or one-step L–H transition can be triggered from the outer-well E  ×  B flow shear originating from the SOL region. From its close relevance to SOL properties, this model appears to provide a possible explanation of the L–H threshold power dependence on magnetic or divertor geometry.