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Active optical boundary recognition with boron powder injection in a magnetic confinement device
Dong Guo1,2, Yuejiang Shi3, Qifeng Xie2
1International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics, State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China.
Scientific Reports
|January 27, 2026
Summary
A new method uses boron powder injection to precisely identify the plasma boundary (Last Closed Flux Surface) in fusion devices. This technique offers real-time, accurate LCFS detection, improving plasma control for future fusion energy systems.
Area of Science:
- Plasma Physics
- Fusion Energy Research
- Diagnostic Techniques
Background:
- Accurate determination of the plasma boundary, specifically the Last Closed Flux Surface (LCFS), is essential for magnetic confinement fusion devices.
- Conventional methods like magnetic reconstructions and passive optical diagnostics face limitations during transient or low-emission plasma conditions.
- Effective plasma control, equilibrium understanding, and confinement optimization rely heavily on precise LCFS identification.
Purpose of the Study:
- To introduce and validate an innovative plasma boundary identification technique using boron powder injection.
- To demonstrate the capability of this method for real-time LCFS detection in spherical torus devices.
- To assess the potential of active boron injection for advanced plasma control in future fusion reactors.
Main Methods:
- Utilizing boron powder injection into the EXL-50U spherical torus device.
- Leveraging the strong, localized visible line radiation emitted by ablated boron particles at the plasma boundary.
- Employing precise camera calibration and boron-filter-based contrast enhancement for accurate boundary visualization.
- Comparing the performance of the boron injection technique against established boundary detection methods.
Main Results:
- Boron ablation provides a clear, real-time marker for LCFS detection.
- The technique achieves high spatial accuracy and fast response.
- Minimal hardware complexity compared to conventional methods.
- Successful demonstration in the EXL-50U spherical torus.
Conclusions:
- Active boron powder injection presents a robust and effective solution for real-time plasma boundary determination.
- This method overcomes limitations of conventional diagnostics, particularly in challenging plasma conditions.
- The technique holds significant promise for enhancing plasma control strategies in future long-pulse, high-performance fusion devices.
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