研究目的
Quantification of the neutral recycling flux in fusion-related toroidal devices is an important issue for achieving a high-performance steady-state discharge, improving the energy confinement time by preventing edge plasma cooling, and assessing numerical simulation results to specify the designs of next-generation devices.
研究成果
The study demonstrated that the accuracy of measuring local atomic spectra using the Zeeman effect can be improved by adopting an emission line at a longer wavelength. The method proved effective for evaluating the local recycling flux and has potential applications in measuring toroidal and poloidal distributions of the recycling flux with multiple viewing chords.
研究不足
The approximation that atomic emission is radially localized may not fully account for the actual extended emission, leading to apparent broadening of the separated spectra. The study also notes that adopting a spectrometer with better wavelength resolution could further reduce uncertainty in the fitting results.
1：Experimental Design and Method Selection:
The study employed a passive spectroscopic method utilizing the Zeeman effect to measure spatially resolved emission spectra from a single diagnostic port without assuming plasma symmetry. The method was applied to a near-infrared helium emission line (He I 1s2s 3S?1s2p 3P, 1083 nm) in the stellarator-heliotron device Heliotron J.
2：Sample Selection and Data Sources:
Deuterium plasma was produced using electron cyclotron heating and neutral beam injection heating, with helium gas introduced for the measurement.
3：List of Experimental Equipment and Materials:
The setup included an objective lens, optical fiber patch chord, and a custom-made interference spectrometer with a tunable Fabry?Perot etalon optimized at 1083 nm.
4：Experimental Procedures and Operational Workflow:
The plasma emission was observed through a fused quartz window, collected using an objective lens, transmitted by an optical fiber, and analyzed using the spectrometer. Spectra were averaged over seven identical discharges to improve the signal-to-noise ratio.
5：Data Analysis Methods:
The superposed spectra were separated using a fitting procedure that considered local intensity, magnetic field strength, atomic velocity, and temperature, with the instrumental function convoluted to the calculated spectrum.
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