Soft x-ray tomography for real-time applications: present status at Tore Supra and possible future developments

Area of Science:

• Plasma physics
• Fusion energy research
• Tomographic imaging

Background:

• The Tore Supra tokamak utilizes a soft x-ray (SXR) tomography system, DTOMOX, for plasma diagnostics.
• Accurate characterization of plasma features is crucial for understanding and controlling fusion processes.

Purpose of the Study:

• To present the DTOMOX system and its recent automated data analysis capabilities.
• To analyze plasma emissivity, magnetic axis positions, and impurity accumulation for improved fusion research.

Main Methods:

• Optimization of the tomographic inversion process for SXR data.
• Real-time characterization of plasma emissivity using shape factors.
• Off-line comparison of magnetic equilibrium solver data with reconstructed emissivity maxima.
• Analysis of specific plasma events like sawtooth crashes and lower hybrid current drive pulses.

Main Results:

• The optimized DTOMOX system enables automated and precise plasma feature extraction.
• A consistent 5 cm discrepancy between the magnetic axis and emissivity maximum was observed, increasing during sawtooth crashes.
• Radially localized tungsten accumulation with in-out asymmetry was detected during lower hybrid current drive operation.

Conclusions:

• The enhanced DTOMOX system offers significant improvements in real-time plasma diagnostics.
• The observed magnetic axis-emissivity discrepancy provides insights into plasma dynamics.
• DTOMOX demonstrates capability for precise localization of impurities, aiding in fusion reactor design and operation.