2D electron density profile evolution during detachment in Super-X divertor L-mode discharges on MAST-U

TL;DR

This study analyzes how 2D electron density profiles evolve during plasma detachment in MAST-U's Super-X divertor, revealing the impact of divertor geometry and power conditions on plasma behavior and comparing measurements with simulations.

Contribution

It provides detailed measurements of electron density evolution during detachment in the Super-X divertor and compares these with SOLPS simulations, highlighting the effects of divertor geometry.

Findings

Long-legged divertors reduce electron density and particle flux at the target.

Deeper detachment correlates with lower temperatures and increased neutral drag.

Simulation results generally agree with experimental density profiles.

Abstract

2D electron density profiles obtained from coherence imaging spectroscopy in different MAST-U divertor conditions are compared. The data includes variations of strike point position, core electron density, and heating power. The improved performance of the long-legged divertors results in a lower electron density and particle flux at the target compared to configurations with smaller strike point major radius, while also being characterized by lower temperatures and deeper detachment. Comparisons against SOLPS simulations generally show good agreement in profile shape along and across the separatrix. The peaking of the electron density downstream of the detachment front is associated with significant neutral drag acting on the plasma flow.