<i>H</i>mode of the W 7-AS stellarator

Abstract

In W 7-AS the H mode has been observed for the first time in a currentless stellarator plasma. H modes are achieved with 0.4 MW electron cyclotron resonance heating at 140 GHz at high density. The H phases display all characteristics known from tokamak H modes including edge localized modes (ELMs). The achievement of the H mode in a shear-free stellarator without toroidal current has consequences on H-mode transition and ELM theories.