H mode of the W 7-AS stellarator.

Abstract

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