Synchronization of Thomson scattering measurements on MAST using an FPGA based "Smart" trigger unit

Area of Science:

• Plasma Physics
• Fusion Energy Research

Background:

• The Mega Ampere Spherical Tokamak (MAST) requires precise plasma diagnostics for operational control and research.
• Previous Thomson scattering systems had limitations in spatial and temporal resolution for studying fast plasma phenomena.

Purpose of the Study:

• To upgrade the MAST Thomson scattering diagnostic for enhanced electron density and temperature measurements.
• To achieve high spatial resolution across the plasma diameter and high temporal resolution for fast events.

Main Methods:

• Implementation of a new Thomson scattering system with 130 measurement points.
• Utilized eight Nd:YAG lasers operating at 30 Hz, capable of 240 measurements per second.
• Developed a field programmable gate array (FPGA) based trigger unit for 100 ns precision laser firing and external event synchronization.

Main Results:

• The upgraded system provides electron density and temperature measurements at 130 points across the 1.5 m plasma diameter.
• Achieved high temporal resolution, with lasers capable of firing in bursts down to the microsecond level.
• Demonstrated accurate and reproducible measurements of fast plasma phenomena through precise trigger synchronization.

Conclusions:

• The upgraded MAST Thomson scattering diagnostic significantly improves the capability for detailed plasma characterization.
• The system's high spatial and temporal resolution is crucial for understanding and controlling fusion plasmas.
• Enables precise investigation of transient plasma events, contributing to advancements in fusion energy research.