Development of a soft x-ray (SXR) array diagnostic system on versatile experiment spherical torus (VEST)

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Diagnostic Systems

Background:

• Understanding plasma behavior is crucial for fusion energy.
• Magnetohydrodynamics (MHD) modes are key plasma instabilities.
• Accurate measurement of plasma properties is essential for control.

Purpose of the Study:

• Develop and validate a new soft x-ray (SXR) array diagnostic system.
• Measure 2D SXR emissivity profiles.
• Identify poloidal mode structures in plasma.

Main Methods:

• Utilized tomographic inversion techniques on line-integrated SXR data.
• Employed two 20-channel SXR detector arrays (absolute extreme ultraviolet photodiode arrays).
• Implemented a filter wheel system for energy-dependent measurements and high-speed data acquisition (up to 125 MHz).

Main Results:

• Successfully acquired 2D SXR emissivity profiles.
• Enabled visualization of plasma instability structures, including MHD modes.
• Demonstrated the system's capability with initial measurements from Ohmic plasma in VEST.

Conclusions:

• The new SXR diagnostic system effectively measures 2D emissivity profiles and identifies poloidal mode structures.
• This advancement provides valuable insights into plasma instabilities.
• The system is a promising tool for fusion research on the VEST device.