High DT Fusion Performance in ELM-Free H-Modes in JET

Associacao EURATOM/IST, Centro de Fusao Nuclear, 1096 Lisbon, CODEX, Portugal1. IntroductionDuring the MKII Divertor campaign the performance characteristics of the Hot-Ion ELM-freeH-mode regime in Deuterium plasmas have been comprehensively explored [1,2].Experiments were carried out up to a plasma current of 4.2 MA and a toroidal field of 3.8 T,with Neutral Beam (NB) heating alone and with NB plus Hydrogen minority Ion CyclotronResonance Heating (ICRH), up to a total input power of about 25 MW.The maximum fusion reactivity is obtained transiently; density and stored energy risecontinuously with time, until the terminating MHD event, which is either a large sawtooth, aGiant ELM or an external kink mode. The identification of the so-called Outer Mode as anideal external kink, driven by the edge current gradient, led to the development of a methodfor its mitigation or avoidance by decreasing the plasma current during the ELM-free phase.As a result the performance, robustness and reliability of the regime have been improved,extending the maximum DD neutron yield to 5.2×10