Far-infrared tangential interferometer/polarimeter design and installation for NSTX-U

Area of Science:

• Fusion Energy Research
• Plasma Physics
• Optical Diagnostics

Background:

• The National Spherical Torus Experiment-Upgrade (NSTX-U) requires precise real-time plasma diagnostics for effective control.
• Previous diagnostic systems may have limitations in providing core electron density data for feedback control loops.

Purpose of the Study:

• To refurbish and reinstall the Far-infrared Tangential Interferometer/Polarimeter (FIReTIP) system on NSTX-U.
• To enable real-time line-integrated core electron density measurements for plasma control.
• To implement real-time vibration compensation and signal correction for enhanced diagnostic accuracy.

Main Methods:

• Refurbishment of the FIReTIP system.
• Integration of a visible light heterodyne interferometer for vibration compensation.
• Utilizing a National Instruments CompactRIO field-programmable gate array for real-time signal processing.

Main Results:

• The refurbished FIReTIP system is being reinstalled on NSTX-U.
• The system will supply real-time line-integrated core electron density measurements.
• Real-time vibration compensation and signal correction mechanisms are incorporated.

Conclusions:

• The enhanced FIReTIP system will provide crucial real-time data for the NSTX-U plasma control system (PCS).
• This facilitates real-time density feedback control, leading to improved plasma stability and performance.
• The integration of advanced optical and processing techniques ensures reliable diagnostic measurements.