Integrated pedestal and core modeling of Joint European Torus (JET) triangularity scan discharges

Abstract

Simulations of four Joint European Torus (JET) [Rebut et al., Nucl. Fusion 25, 1011 (1985)] type I ELMy high confinement mode discharges in a triangularity scan are carried out using the JETTO integrated modeling code [Erba et al., Plasma Phys. Contolled Fusion 39, 261 (1997)] with a predictive core transport model and a pedestal model that includes the effects of edge localized modes (ELMs). The pedestal pressure gradient is limited by the magnetohydrodynamic (MHD) ballooning mode instability, which triggers ELM crashes in these simulations. The validation of the pressure gradient limit used in the simulations is confirmed by a stability analysis carried out using the HELENA and MISHKA codes [Mikhailovskii et al., Plasma Phys. Rep 23, 713 (1997)]. The MHD stability analysis includes infinite-n ideal ballooning, finite-n ballooning, and low-n kink/peeling modes. It is shown that higher triangularity plasmas have easier access to the second stability region, which allows the edge pressure gradients in the higher triangularity discharges to increase to higher levels.

ELM triggering conditions for the integrated modeling of H-mode plasmas

“…4a and b). This observation is consistent with other MHD stability analysis [32] and the conclusion that higher triangularity discharges can more easily access the second ballooning stability limit region of parameter space [3]. As result, ELMs in lower triangularity discharges are much more frequent than ELMs in higher triangularity discharges (as shown in Fig.…”

“…The high triangularity discharge has a larger stable region than the low triangularity discharge, which is consistent with experimental results and other MHD stability analysis [32]. In particular, the higher triangularity discharges have a larger second stability region, which is also consistent with the conclusion that higher triangularity discharges can more easily access the second ballooning stability region of parameter space [3]. The peeling-ballooning threshold shown in Fig.…”

“…One of the effective ways to test ideas for physics models is to combine them within an integrative modeling code and compare the simulation results with the experiments. Integrated modeling studies that self-consistently take into account the effects of the plasma edge have been developing during the last decade [1][2][3][4][5]. Some of these simulations are rather comprehensive and take into account MHD equilibrium, turbulent anomalous radial transport, neutral gas transport, atomic and molecular physics, and plasma-wall interactions.…”

Effect of isotope mass on simulations of the high-mode pedestal and edge localized modes

“…This transport barrier results in a pedestal, which is a narrow region with steep gradients in the plasma temperature, density, and pressure profiles near the edge of the plasma. [5][6][7][8][9] H-modes are usually accompanied by ELMs, which involve periodic losses of plasma that occur on a short time scale ͑on the order of or less than a millisecond͒ near the boundary of the plasma. Each ELM crash results in an avalanche-like burst of particles and energy at the edge of the plasma, along with a brief deterioration of plasma confinement.…”

Integrated ELM Modelling

“…In some work, the ad hoc approach described above has been extended to include a stability criterion for peeling modes as well [26][27][28]. In these studies, the MHD stability codes HELENA [12] and MISHKA-1 have been used to calibrate the stability limits and the model has then been used in triangularity, power and isotope scans for JET and in modelling of ITER.…”