B. Chatthong1, W. Kanjanaput2, J. Promping3, R. Picha3 and T. Onjun2 1School of Manufacturing Systems and Mechanical Engineering, Sirindhorn International Institute of Technology, Thammasat University, Pathum Thani, Thailand 2School of Manufacturing Systems and Mechanical Engineering, Sirindhorn International Institute of Technology, Thammasat University, Pathum Thani, Thailand 3Thailand Institute of Nuclear Technology, Bangkok, Thailand

in Tokamaks W. Kanjanaput , T. Onjun, M. Ottaviani and X. Garbet 1 School of Manufacturing Systems and Mechanical Engineering, Sirindhorn International Institute of Technology, Thammasat University, Pathum Thani, 12120, Thailand 2 CEA, IRFM, 13108 Saint-Paul-Lez-Durance, France Introduction Magnetic reconnection is one of serious issues in magnetic confinement fusion research as it can disrupt a plasma and degrades fusion performance. The reconnection of magnetic field lines, a consequence of MHD instabilities, changes the topology of magnetic surfaces, via the formation of magnetic islands. Plasma particles and energy are quickly transported along these magnetic field lines thereby increasing the effective radial transport in the island region. Magnetic reconnection, however, can be beneficial. For example, it can be used to increase the plasma transport at the edge to reduce the ELMs amplitude during H-mode plasma. In this study, we focus on the interaction of coupled magnetic islands and their effect on the plasma profiles evolution. Model of NTMs transport in tokamak In this work, the ISLAND module [1, 2], which is used to predict the saturated width of magnetic island, is improved in terms of robustness, reliability, and accuracy. The size of a magnetic island during the initial stage increases exponentially until it reaches a second state that the growth rate is reduced due to nonlinear effects. The island size ultimately saturates to a finite width. The evolution of the magnetic island width is usually modelled by the Rutherford equation [3]

An investigation of fusion power and bootstrap current fraction of the European Power Plant Conceptual Study (PPCS) DEMO designs is carried out using BALDUR integrated predictive modelling code [1]. The PPCS summarizes the conceptual designs for commercial fusion power plants [2]. In this work, a combination of anomalous transport model (MMM95) and neoclassical transport model (NCLASS) is used to simulate core transport. The boundary condition of the plasma is set at the top of the pedestal, which is described by the pedestal model based on normalized pressure width model [3]. The simulations aim to study the performance of the five PPCS models, i.e. PPCS A, AB, B, C and D. It was found that as the NBI heating power is changed from 20–90 MW, the fusion power varies in the range of 5.1– 5.7 GW for models A and AB, 4.1–4.4 GW for model B, 0.8–1.4 GW for model C and 0.02– 0.4 GW for model D. The bootstrap current fractions from the simulations are 0.40-0.41 for models A and AB, 0.38-0.39 for model B, 0.39-0.43 for model C and 0.12-0.42 for model D. Model D yields the lowest performance and is found to be in L-mode when NBI heating is low enough. The optimum point for fusion power under these parameters will be discussed.

Introduction To obtain high fusion performance in tokamak reactors, high confinement mode (H-mode) plasma [1] is needed. The key success of H-mode is the formation of a transport barrier near the edge, often called a “pedestal” (see Figure 1). In this work, a sandpile model [1, 2] is used to study the plasma behaviours during the performance-mode operational regime. The pedestal is modeled based on the experimental observation that the strong gradient is formed during the transition from L-mode to H-mode. When the transport barrier appears, the temperature and density over the whole plasma increase, and, consequently, the energy confinement improves. The pellet injection which is one of refuelling techniques can be introduced to induce the formation of H-mode. Pellet size and velocity have significant impact on the H-mode formation, and they will be the focus of this study.