Models for H-Mode Pedestal Temperature and Predictions for Future Tokamak Designs

Studies of type 1 ELMy H-mode pedestals are carried out using 0 D and 1.5 D approaches. In the 0 D study, predicted pedestal temperatures are compared with 533 data points. The pedestal temperature models, with pedestal width based on magnetic and flow shear stabilization and neutral penetration, yield an RMSE of 32% and 53.4%, respectively, when compared with data. In the 1.5 D studies, the pedestal models are used together with a core transport model in the integrated predictive transport code JETTO. In simulations of type 1 ELMy H-modes using the JETTO code, when a pedestal width model based on neutral penetration is used, the pedestal width and pressure are significantly under-predicted and the ELM frequency obtained is that expected for type 3 rather than type 1 H-mode plasmas. In contrast, the simulations using a pedestal width based on magnetic and flow shear stabilization yield better agreement for the pressure profiles and the ELM frequency is appropriate for type 1 ELMs. Consequently, the simulations indicate that magnetic and flow shear stabilization plays a more significant role in determining the width of type 1 ELMy H-mode pedestals than does neutral penetration. The pedestal temperature model, using a pedestal width based on magnetic and flow shear stabilization, together with the MMM95 core transport model, is used in the BALDUR code to predict the performance of ITER. At the ITER design point, the simulation yields a pedestal temperature of 2.74 keV and an alpha power of 89.3 MW, corresponding to fusion Q of 11.2