Soft x-ray tomography on the high field spherical tokamak ST40

Area of Science:

• Nuclear Fusion Energy
• Plasma Physics
• High-Field Spherical Tokamak Research

Background:

• Tokamak Energy Ltd. operates the ST40 high-field spherical tokamak as part of its commercial fusion plant development roadmap.
• Understanding plasma confinement and the fusion triple product is crucial for advancing fusion energy.
• Diagnosing energy loss mechanisms is essential for optimizing tokamak performance.

Purpose of the Study:

• To expand the physics basis of high-field spherical tokamaks by characterizing confinement and the fusion triple product.
• To investigate key plasma energy loss mechanisms using bolometers and sensitive diodes.
• To analyze core magnetohydrodynamic (MHD) activity, such as sawtooth crashes, impacting plasma confinement.

Main Methods:

• Deployment of a new 16-channel, midplane, tangential, Beryllium-filtered diode array.
• Resolution of magnetohydrodynamic instabilities up to 100 kHz.
• Tomographic inversion of radiation profiles, validated against other ST40 diagnostics.

Main Results:

• The new diode system successfully resolves MHD instabilities.
• Tomography provides radial emissivity measurements across various operating scenarios.
• The diagnostic system aids in inferring total radiated power losses and plasma composition.

Conclusions:

• The implemented diagnostic system enhances the characterization of plasma energy loss mechanisms in the ST40.
• Tomographic analysis of radiation profiles offers valuable insights into plasma behavior.
• Future implementation of soft X-ray cameras will further improve diagnostic capabilities for fusion research.