A dual-band adaptor for infrared imaging

Area of Science:

• Plasma Physics
• Infrared Imaging Technology
• Materials Science

Background:

• Accurate temperature measurement is critical for fusion energy research, particularly for components like divertors.
• Surface emissivity variations in liquid lithium divertors pose challenges for traditional single-band infrared thermography.
• The National Spherical Tokamak Experiment (NSTX) requires high-speed thermal imaging capabilities.

Purpose of the Study:

• To develop a novel imaging adapter for converting a single-band infrared camera into a dual-band system.
• To enable high-speed, emissivity-independent thermography for the NSTX.
• To assess the performance of dual-band infrared imaging in characterizing NSTX divertor conditions.

Main Methods:

• Modification of a commercial visible-range optical splitter for medium (4-6 μm) and long (7-10 μm) wavelength infrared operation.
• Integration of a dichroic beamsplitter with >95% efficiency for IR channel separation.
• Utilizing ZnSe optics and cutoff filters for broadband infrared imaging.
• Performing in-situ and ex-situ calibration and collecting preliminary data during NSTX plasma discharges.

Main Results:

• Successful development and implementation of a dual-band IR imaging adapter for NSTX.
• Demonstration of side-by-side projection of two IR channels onto a single camera detector.
• Acquisition of preliminary thermal data from the NSTX divertor during plasma operations.
• Presentation of contrasting results between dual-band and single-band infrared imaging.

Conclusions:

• The developed dual-band IR imaging adapter effectively extends a standard IR camera's capability for high-speed thermography.
• Dual-band infrared imaging offers significant advantages in temperature measurement accuracy by mitigating emissivity variations.
• This technology is well-suited for monitoring challenging environments like the liquid lithium divertor on NSTX.