Dynamics of scrape-off layer filaments in detached conditions

TL;DR

This study uses 3D fluid simulations to analyze filament dynamics in detached plasma conditions, revealing how detachment affects filament size, velocity, and the critical size, with neutral evolution having minimal impact.

Contribution

It provides new insights into filament behavior during plasma detachment, highlighting the impact on critical filament size and velocity trends in detached conditions.

Findings

Filament velocity generally decreases with increasing background density.

A temporary increase in radial velocity occurs at detachment onset.

Detached conditions increase the critical filament size, reversing attached condition trends.

Abstract

The here presented work studies the dynamics of filaments using 3D fluid simulations in the presence of detached background profiles. It was found that evolving the neutrals on the time-scale of the filament did not have a significant impact on the dynamics of the filament. In general a decreasing filament velocity with increasing plasma background density has been observed, with the exception of detachment onset, where a temporarily increase in radial velocity occurs. The decreasing trend with temporary increase was found for filaments around the critical size and larger, while smaller filaments where less affected by detachment. With detachment the critical filament size increased, as larger filaments were faster in detached conditions. This breaks the trend of attached conditions, where the critical size decreases with increasing density.