MHD-calibrated ELM model in simulations of ITER

Thawatchai Onjun (1) , Vassili Parail (2) , Glenn Bateman (3) , Arnold H. Kritz (3) , Gerrard Corrigan (2) , David Heading (2) , Johnny Lönnroth (4) , Howard R. Wilson (2) , Alex Dnestrovskij (5) , Guido T. A. Huysmans (6) , Alexei Pankin (7)

1 Sirindhorn International Institute of Technology
2 EURATOM/UKAEA Fusion Association
3 Lehigh University Physics Department
4 Association EURATOM-TEKES
5 NRC KI - National Research Center "Kurchatov Institute"
6 Service de réanimation médicale
7 SAIC

Self-consistent simulations of ITER have been carried out using the JETTO integrated modeling code in which theory motivated models are used for the H-mode pedestal and for the stability conditions that lead to the ELM crashes. Transport is described by combining the anomalous Mixed Bohm/gyro-Bohm model with the NCLASS neoclassical transport model. In the pedestal region, the anomalous transport is suppressed and the neoclassical transport dominates. The steep edge pressure gradient and large bootstrap current can lead to an MHD instability, which results in an ELM crash. In the simulations, an ELM crash can be triggered either by a pressure-driven ballooning mode or by a current-driven peeling mode. The equilibrium and MHD stability analyses codes, HELENA and MISHKA, are used to evaluate the edge stability of the plasma just prior to an ELM crash in order to calibrate and confirm the validity of the stability criteria used to trigger ELMs in the JETTO simulations. The MHD stability analyses include infinite-n ideal ballooning modes, finite-n ballooning modes, and low-n kink/peeling modes. At the reference design point (with 40 MW auxiliary heating), the ion temperature at the top of the pedestal before each ELM crash is determined to be approximately 4 keV, with 19 keV at the plasma center. The alpha heating power is approximately 130 MW, which results in a fusion Q of 15.5. It is observed in the simulations that if the auxiliary heating power is increased, the ion temperature at the top of the pedestal and the central ion temperature remain nearly unchanged. As a consequence, there is nearly the same alpha power production so that the fusion Q decreases with increasing auxiliary heating power. It is also found in these simulations that all of the ELM crashes are triggered by finite-n ballooning modes and that the pedestal shear and pressure gradient indicate access to second stability. Access to second stability allows high pressure gradients within the pedestal and, consequently, the high temperatures at the top of the pedestal that are needed to produce fusion Q values in ITER of 10 or greater.

Domaines: Physique des plasmas [physics.plasm-ph]

Thawatchai Onjun, Vassili Parail, Glenn Bateman, Arnold H. Kritz, Gerrard Corrigan, et al.. MHD-calibrated ELM model in simulations of ITER. 2004. ⟨hal-00002045v3⟩