Observation of confined current ribbon in JET plasmas

TL;DR

This paper reports the discovery of a localized, co-rotating current ribbon inside JET plasmas, which influences plasma stability and delays edge localized modes, providing new insights into plasma behavior.

Contribution

It identifies a novel current structure in JET plasmas, revealing its characteristics, formation conditions, and impact on plasma stability, advancing understanding of plasma edge phenomena.

Findings

Identified a localized current ribbon in JET plasmas.

The structure is co-rotating and located at the pedestal top.

It delays the onset of the first ELM.

Abstract

we report the identification of a localised current structure inside the JET plasma. It is a field aligned closed helical ribbon, carrying current in the same direction as the background current profile (co-current), rotating toroidally with the ion velocity (co-rotating). It appears to be located at a flat spot in the plasma pressure profile, at the top of the pedestal. The structure appears spontaneously in low density, high rotation plasmas, and can last up to 1.4 s, a time comparable to a local resistive time. It considerably delays the appearance of the first ELM.