Measurement of peeling mode edge current profile dynamics

Area of Science:

• Plasma physics
• Fusion energy research
• Magnetohydrodynamics

Background:

• Edge localized modes (ELMs) are detrimental instabilities in fusion plasmas.
• Understanding peeling modes is crucial for controlling ELMs.
• Low aspect ratio tokamaks present unique plasma edge conditions.

Purpose of the Study:

• To investigate the occurrence and characteristics of peeling modes in limited plasmas.
• To correlate peeling mode activity with edge plasma parameters.
• To compare experimental observations with theoretical predictions.

Main Methods:

• Experiments conducted on a low aspect ratio tokamak.
• Measurements of edge current density (J(edge)) and magnetic field (B).
• Analysis of edge-localized electromagnetic activity and toroidal mode numbers (n).

Main Results:

• Peeling modes were observed at high J(edge) (~0.1 MA/m²) and low B (~0.1 T).
• Activity showed low toroidal mode numbers (n≤3) and scaled with J(edge)/B.
• Formation of field-aligned, current-carrying filaments from initial perturbations.

Conclusions:

• Experimental evidence supports the theoretical understanding of peeling modes.
• Peeling modes are an important instability mechanism for ELM activity.
• Further research can inform strategies for ELM mitigation in fusion devices.