A potential optical approach for diagnosis of the local magnetic field near the surface of the first wall/divertor tiles by Zeeman effect using polarization-resolved laser-induced breakdown spectroscopy

Huace Wu, Ding Wu, Cong Li, Zhenhua Hu, Fang Ding, Ran Hai, Hongbin Ding, the EAST Team2024年8月Nuclear FusionIF 3 出版社

Magnetic field measurement is the basic diagnosis to obtain the physical engineering parameters of magnetic confinement fusion device and the macro information of plasma discharge. The real-time diagnosis of magnetic field distribution near the plasma-facing components (PFCs) surface provides the important information on the migration and transport model of key elements. In this work, a remote, in-situ approach for the magnetic field measurement near the surface of PFCs by the polarization-resolved laser-induced breakdown spectroscopy (LIBS) based on Zeeman effect is proposed and implemented. The Zeeman characteristics of the emission spectra of laser-induced W, Mo and C plasmas were verified in the laboratory by using different magnetic field configurations. According to the polarization characteristics of the Zeeman sublines of the LIBS spectrum, the intensity and direction of the external local magnetic field were successively identified by using a linear polarizer. Subsequently, a linear array fiber was utilized to determine the polarity of the external magnetic field. And finally, the magnetic field intensity near the lower edge surface of the tungsten baffle of the Experimental Advanced Superconducting Tokamak (EAST) upper divertor was measured when the field coils were demagnetized. This method can supplement the experimental data near the PFCs for the magnetic field configuration of the magnetic confinement fusion device and provide a reference for the wall element analysis model diagnosed by LIBS.

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ENThis paper should be read by fusion researchers, plasma physicists, and engineers working on diagnostic systems for magnetic confinement fusion devices. The technique described can be valuable for improving the understanding of plasma-wall interactions and developing more accurate models for the behavior of fusion reactors.#FusionDiagnostics #PlasmaSpectroscopy #MagneticFieldMeasurement #ZeemanEffect #LaserInducedBreakdownSpectroscopy

This paper presents a novel technique to measure the local magnetic field near the surface of plasma-facing components in fusion devices using polarization-resolved laser-induced breakdown spectroscopy. By analyzing the Zeeman effect on the emission spectra of laser-induced plasmas, the intensity and direction of the magnetic field can be determined. This method can provide important data for understanding the migration and transport of elements on the first wall and divertor tiles, which is crucial for fusion reactor operation and maintenance.