Effects of ripple-induced ion thermal transport on H-mode plasma performance

Lnnroth, J.-S.*; Parail, V.*; Hynnen, V.*; Johnson, T.*; Kiviniemi, T.*; Oyama, Naoyuki; Beurskens, M.*; Howell, D.*; Saibene, G.*; de Vries, P.*; Hatae, Takaki; Kamada, Yutaka; Konovalov, S.*; Loarte, A.*; Shinohara, Koji; Tobita, Kenji; Urano, Hajime; JET-EFDA Contributors*

It is investigated whether differences in the MHD stability of the pedestal, including effects of plasma rotation and aspect ratio, can explain the results of JET/JT-60U similarity experiments. As a result, these mechanisms fail to explain the experimental observations. Therefore, the effects of ripple losses on H-mode performance were investigated. The analysis shows that ripple losses of thermal ions can affect H-mode plasma performance very sensitively. Orbit-following simulations indicate that losses due to diffusive transport give rise to a wide radial distribution of enhanced ion thermal transport, whereas non-diffusive losses have a very edge-localized distribution. In predictive transport simulations with an energy sink term in the continuity equation for the ion pressure representing non-diffusive losses, reduced performance as well as an increase in the ELM frequency are demonstrated.