Experimental study on edge energetic electrons in EXL-50 spherical torus
Abstract
A significant number of confined energetic electrons have been observed outside the Last Closed Flux Surface (LCFS) of the solenoid-free, ECRH sustained plasmas in the EXL-50 spherical torus. Several diagnostics have been applied, for the first time, to investigate the key characters of energetic electrons. Experiments reveal the existence of high-temperature low density electrons, which can carry relatively a large amount of the stored energy. The boundary between the thermal plasma and the energetic electron fluid appears to be clearly separated and the distance between the two boundaries can reach tens of centimeters (around the size of the minor radius of the thermal plasma). This implies that the Grad-Shafranov equilibrium is not suitable to describe the equilibrium of the EXL-50 plasma and a multi-fluid model is required. Particle dynamics simulations of full orbits show that energetic electrons can be well confined outside the LCFS. This is consistent with the experimental observations.
Cite
@article{arxiv.2112.10315,
title = {Experimental study on edge energetic electrons in EXL-50 spherical torus},
author = {Dong Guo and Yuejiang Shi and Wenjun Liu and Yunyang Song and Tiantian Sun and Bing Liu and Yingying Li and Xiaorang Tian and Guosong Zhang and Huasheng Xie and Y. K. Martin Peng and Minsheng Liu},
journal= {arXiv preprint arXiv:2112.10315},
year = {2025}
}