Similar Modification of Intermittent Density Bursts by Electrode Biasing and Dynamic Ergodic Divertor in the TEXTOR Tokamak

TL;DR

This study compares how electrode biasing and dynamic ergodic divertor regimes similarly modify edge plasma density bursts in the TEXTOR tokamak, highlighting potential for contactless plasma control.

Contribution

It demonstrates that both electrode biasing and DED regimes similarly alter intermittent plasma density bursts, offering a new approach for external plasma turbulence control.

Findings

Burst rate increases with biasing and DED.

Burst duration decreases under both regimes.

Radial electric field modification affects turbulence dynamics.

Abstract

Intermittent positive bursts of plasma density detected by Langmuir probes at the edge of the TEXTOR tokamak are investigated. Burst statistical properties and temporal characteristics together with their radial dependence are studied in two different regimes - with electrode biasing and dynamic ergodic divertor (DED). Similar modification of intermittent burst characteristics are observed. Namely, the average burst rate increases and the average burst duration decreases compared to Ohmic conditions. Statistical properties are also modified in the same way in both regimes. The reason is that biasing and certain regimes of DED cause the modification of radial electric field which affects similarly the dynamics of coherent turbulent structures and plasma transport through ErxBt induced sheared poloidal rotation. Thus, after detailed investigations and refinement, certain regimes of DED can be used as "contactless biasing" for the external control of plasma turbulent transport in fusion devices.