PEP-39 Update from JET-ILW: Configuration effects on L-H power threshold and H-mode

Abstract

In JET-ILW Corner (CC) plasmas the L-H transition power threshold (PLH) is higher than in the Horizontal Target (HT) ones, indicating poorer L-mode confinement in Corner. The ne,min dependence on both plasma configuration and plasma current was shown. In D plasmas, typically ne,min(CC)~0.3 of the Greenwald density (nGW), while ne,min(HT)~0.4 nGW, for various Btor and Ip L-H transition datasets. A reduction in ne,min when Ip is lower was shown. Despite the fact that HT has lower PLH, for the same gas fuelling and input power, the H-mode in HT has poorer confinement than CC. In the CC time-window density is lower and temperatures higher, and steady large ELMs are observed. In the HT time window, pedestal density is higher and temperatures lower, a mixture of small and large ELMs is present. A higher ratio of heating power to PLH threshold does not correlate with good confinement or steady type I ELMy regime. Additional L-H transition experiments investigating the configuration effect and the relationship between Ip and ne,min (at fixed Btor) were requested, even if in Carbon devices.