Four-dimensional conditional averaging tomography of rotating plasma ejection from cylindrical detached plasma

Area of Science:

• Plasma physics
• Fusion energy research
• Diagnostic techniques

Background:

• Detached plasma formation is crucial for mitigating heat loads in magnetic confinement fusion devices.
• Understanding the dynamics of plasma ejections is key to improving plasma-wall interaction control.

Purpose of the Study:

• To develop and apply a novel analysis technique for investigating the spatiotemporal behavior of rotating radial ejection events in detached plasma.
• To elucidate the role of these events in local heat load reduction on device walls.

Main Methods:

• Utilized conditional averaging, sliding window analysis, and tomography.
• Employed a high-speed camera and electrostatic probe on the linear plasma device NAGDIS-II.
• Reconstructed four-dimensional (4D) emission structures (time and 3D space).

Main Results:

• Clarified the 4D behavior of detached plasma emission structures.
• Identified a rotating distorted structure as a precursor to radial and axial transport.
• Demonstrated the contribution of these events to local heat load reduction.

Conclusions:

• The proposed analysis technique effectively reveals the complex dynamics of detached plasma.
• Rotating radial ejections play a significant role in managing heat flux in fusion devices.
• The method is broadly applicable to analyzing short-term rotating structures, particularly in linear plasma devices.