Reconstruction of soft x-ray emission in MAST Upgrade

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Magnetohydrodynamics

Background:

• Fast ion confinement is critical for fusion reactor operation, impacting plasma heating and current drive.
• Interactions between fast ions and magnetohydrodynamic (MHD) instabilities degrade fusion performance.
• Accurate spatial measurements of MHD instabilities are needed to constrain numerical models.

Purpose of the Study:

• To investigate the effectiveness of Soft X-ray (SXR) tomography for reconstructing MHD instabilities.
• To evaluate different tomographic reconstruction models using synthetic SXR emissions.
• To assess the impact of additional intersecting lines of sight on reconstruction accuracy.

Main Methods:

• Utilized synthetic SXR emissions generated from TRANSP/NUBEAM simulations on the Mega Ampere Spherical Tokamak Upgrade (MAST-U) device.
• Employed SXR tomography, a technique reconstructing 2D SXR emissivity profiles from line-integrated measurements.
• Compared various tomographic reconstruction models and analyzed the effect of adding intersecting SXR lines of sight.

Main Results:

• SXR tomography successfully reconstructed the 2D profile of SXR emissivity, revealing the spatial structure of instabilities.
• The addition of two extra fans of intersecting SXR lines of sight significantly enhanced the accuracy of the tomographic reconstructions.
• Different tomographic reconstruction models showed varying performance, highlighting the importance of model selection.

Conclusions:

• SXR tomography is a valuable tool for diagnosing MHD instabilities in fusion devices.
• Incorporating additional intersecting SXR lines of sight is crucial for improving diagnostic accuracy.
• The findings support the use of SXR tomography for validating fast ion interaction models in fusion research.