Performance and data analysis aspects of the new DIII-D monostatic profile reflectometer system

Area of Science:

• Plasma physics
• Fusion energy research
• Microwave diagnostics

Background:

• Profile reflectometry is crucial for understanding plasma behavior in fusion devices.
• Traditional reflectometer systems often require complex antenna configurations.
• The DIII-D tokamak provides a platform for testing advanced plasma diagnostic techniques.

Purpose of the Study:

• To introduce and experimentally validate a new frequency-modulated profile reflectometer system with a monostatic antenna.
• To assess the system's capability in measuring electron density (ne) profiles under various plasma conditions, including vertical offsets.
• To demonstrate the system's performance in terms of accuracy, temporal, and spatial resolution.

Main Methods:

• Installation of a novel monostatic reflectometer system on the DIII-D tokamak.
• Utilizing overmoded, broadband transmission waveguide and dual-polarization techniques.
• Employing the GENRAY raytracing code to determine probe beam trajectories for profile reconstruction.
• Testing the system with L-mode plasmas exhibiting vertical shifts.

Main Results:

• Successful reconstruction of electron density (ne) profiles with L-mode plasmas vertically shifted by over 10 cm.
• Demonstrated capability to measure ne profiles with plasma vertical offsets up to ±17 cm.
• Obtained accurate, high time and spatial resolution density profile measurements across diverse DIII-D operational conditions, including L-H transitions.

Conclusions:

• The new monostatic profile reflectometer system is a viable and effective diagnostic for measuring electron density profiles in tokamaks.
• The system demonstrates robust performance, accurately capturing density profiles even with significant plasma vertical displacements.
• This advancement offers improved capabilities for fusion plasma research and diagnostics.