Development of a 3-D tomography technique for Large Helical Device bolometry using EMC3-EIRENE grids

Area of Science:

• Plasma physics
• Fusion energy research
• Diagnostic techniques

Background:

• Bolometry is crucial for measuring plasma radiation in fusion devices.
• Existing tomography techniques have limitations in resolution and coverage.
• Accurate plasma diagnostics are essential for understanding and controlling fusion reactions.

Purpose of the Study:

• To develop and validate a novel three-dimensional (3-D) tomography technique for the Large Helical Device (LHD) bolometry system.
• To improve the spatial resolution and accuracy of plasma radiation measurements.
• To compare the performance of a new 3-D smoothing method against conventional techniques.

Main Methods:

• Development of a 3-D tomography technique using EMC3-EIRENE mesh coordinates.
• Integration of resistive bolometers and infra-red imaging video bolometers (1088 channels total).
• Application of 3-D extended relative gradient smoothing and tetrahedralization for geometry matrix calculation.

Main Results:

• Achieved a high resolution of 59,400 voxels in the reconstructed solution.
• Obtained physically meaningful solutions with minimal negative power, validated by phantom emission and synthetic data.
• Demonstrated superior performance of 3-D extended relative gradient smoothing compared to conventional minimum Fisher regularization.

Conclusions:

• The developed 3-D tomography technique significantly enhances bolometric measurements in the LHD.
• The combination of multiple bolometer types and advanced 3-D smoothing provides more accurate and comprehensive plasma radiation data.
• This advancement contributes to better plasma diagnostics and control in fusion research.