A wide range real-time synchronous demodulation system for the dispersion interferometer on HL-2M

Area of Science:

• Plasma Physics
• Fusion Energy
• Interferometry

Background:

• Tokamak devices require precise plasma diagnostics for operational control and research.
• Dispersion interferometry is a key technique for measuring plasma density.
• Real-time data acquisition and processing are crucial for dynamic plasma behavior.

Purpose of the Study:

• To develop and implement a real-time synchronous demodulation system for a dispersion interferometer on the HL-2M tokamak.
• To improve the accuracy and temporal resolution of plasma density measurements.
• To enable real-time plasma density feedback control.

Main Methods:

• Utilized a phase extraction method based on the ratio of modulation amplitudes.
• Implemented a real-time synchronous demodulation algorithm using a high-performance field-programmable gate array (FPGA) with pipeline processing.
• Applied a fringe jump correction algorithm to track rapid plasma density fluctuations.
• Employed the Peripheral Component Interconnect Express (PCIe) protocol for high-speed data transfer.

Main Results:

• Achieved a temporal resolution of 100 nanoseconds for real-time density feedback.
• Demonstrated a wide measurement range of up to 2.28 × 10^22 m^-2.
• Obtained high-precision plasma density measurements.
• Successfully followed fast plasma density changes.

Conclusions:

• The developed real-time synchronous demodulation system significantly advances plasma density measurement capabilities for tokamaks.
• The system's high temporal resolution and wide measurement range are critical for fusion energy research and control.
• The integration of FPGA and PCIe technologies enables efficient real-time data processing and feedback.