Improved design for Heliotron J soft X-ray diagnostic for tomographic reconstruction studies

Area of Science:

• Plasma physics
• Fusion energy research

Background:

• Accurate plasma boundary and mode structure identification is crucial for magnetohydrodynamics (MHD) equilibrium and stability studies.
• Imaging diagnostics, particularly soft X-ray (SX) tomography, offer direct measurement capabilities but face challenges due to limited angles and ill-posed inverse problems.
• Heliotron J (H-J), a medium-sized heliotron device, requires precise quantitative identification of plasma characteristics due to its unique magnetic geometry.

Purpose of the Study:

• To describe tomographic reconstruction of simulated SX measurements for the Heliotron J device.
• To evaluate the effectiveness of the current SX diagnostic design for H-J.
• To propose a new SX diagnostic design with enhanced capabilities for tomographic reconstructions.

Main Methods:

• Utilized simulated soft X-ray (SX) measurements from the Heliotron J (H-J) device.
• Employed the Phillip-Tikhonov regularization method to address the ill-posed inverse problem inherent in limited-angle tomography.
• Focused on quantitative identification of plasma boundary shape and mode structure.

Main Results:

• Demonstrated the feasibility of tomographic reconstruction for H-J's unique magnetic geometry using simulated SX data.
• Highlighted the dependence of reconstructed profiles on measurement quality and inversion algorithms.
• Identified areas for improvement in diagnostic design for more accurate reconstructions.

Conclusions:

• Tomographic reconstruction of SX data is vital for understanding H-J's plasma behavior.
• The Phillip-Tikhonov regularization effectively tackles the inversion challenges.
• A new SX diagnostic design is proposed to enhance reconstruction capabilities, particularly for high poloidal number perturbations.