Onion-peeling inversion of stellarator images

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Astrophysical Diagnostics

Background:

• Stellarator devices are crucial for magnetic confinement fusion research.
• Accurate measurement of plasma emissivity profiles is essential for understanding and controlling stellarator performance.
• Traditional methods for inferring emissivity can be complex and computationally intensive.

Purpose of the Study:

• To develop and validate a novel, computationally efficient technique for determining the emissivity profile of stellarator plasmas.
• To enable the reconstruction of 3D emissivity distributions from 2D imaging data.
• To provide a practical tool for analyzing plasma behavior in devices like the Columbia Neutral Torus (CNT).

Main Methods:

• An 'onion-peeling' algorithm is employed, treating each camera pixel as an integral of emission along a line-of-sight.
• Plasma flux surfaces are discretized into layers of uniform emissivity.
• A system of linear equations is formulated and solved, leveraging known flux surface topology, to determine layer emissivities.

Main Results:

• The onion-peeling technique successfully reconstructs emissivity profiles from 2D visible images.
• Initial application to the Columbia Neutral Torus (CNT) demonstrates the method's feasibility.
• The technique provides layer-by-layer emissivity values, offering detailed spatial information.

Conclusions:

• The developed onion-peeling technique offers a robust and accessible method for inferring stellarator plasma emissivity.
• This approach simplifies the analysis of 2D imaging data for plasma diagnostics.
• The method holds promise for advancing the understanding and optimization of stellarator confinement.