Tomographic analysis of tangential viewing cameras (invited)

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Diagnostic Techniques

Background:

• Tokamak devices utilize visible light cameras for observing plasma behavior and emissions.
• Coherence imaging spectroscopy (CIS) on DIII-D captures interferograms encoding line-integrated velocity.

Purpose of the Study:

• To develop tomographic methods for determining local plasma emissivity and parallel velocity from tangential camera views.
• To address the inverse problem of reconstructing 3D plasma properties from 2D diagnostic data.

Main Methods:

• Modeling 2D camera images as line-of-sight integrals through a discrete axisymmetric grid.
• Calculating a sparse response matrix to represent image formation as a matrix-vector multiplication.
• Developing techniques for precise camera geometry determination and handling spatially varying physical quantities.
• Implementing distributed computing across a heterogeneous cluster for large-scale matrix calculations.
• Utilizing iterative techniques to solve the resulting sparse linear system.

Main Results:

• A robust method for tomographic inversion of coherence imaging spectroscopy data was established.
• The developed methods allow for the reconstruction of local plasma emissivity and parallel velocity.
• The computational approach is scalable and can be distributed across high-performance computing resources.

Conclusions:

• The presented tomographic analysis provides a powerful tool for understanding plasma dynamics in tokamaks.
• This technique enhances the diagnostic capabilities for fusion energy research by enabling detailed 3D plasma reconstruction.
• The computational framework is adaptable for various diagnostic setups and plasma conditions.