Design and implementation of a full profile sub-cm ruby laser based Thomson scattering system for MAST

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Diagnostic Systems

Background:

• The Mega-ampere spherical tokamak (MAST) utilizes two Thomson scattering (TS) systems for plasma diagnostics.
• Independent electron temperature and density profiles are crucial for tokamak operation and research.

Purpose of the Study:

• To detail the design and implementation of a major upgrade to the ruby TS system on MAST.
• To improve the spatial resolution, accuracy, and data acquisition capabilities of the ruby TS diagnostic.

Main Methods:

• The upgraded ruby TS system employs a high-energy pulsed laser and advanced collection optics.
• A new intensified CCD camera enables high-speed, dual-snapshot measurements.
• Automated system operation facilitates seamless integration with MAST discharges.

Main Results:

• The system achieves 512 measurement points across the major radius with 7 mm spatial resolution.
• Accurate measurements of electron temperature (T(e)) and density (n(e)) are obtained with low estimated errors (<4% T(e), <3% n(e)).
• The system can acquire two profiles with a minimum time separation of 230 μs, enabling dynamic plasma studies.

Conclusions:

• The upgraded ruby TS system significantly enhances diagnostic capabilities for MAST.
• Improved spatial and temporal resolution provides more detailed insights into fusion plasma behavior.
• The system's accuracy and automation contribute to more effective tokamak research.