Achievement of 1 MA discharges in hydrogen–boron plasmas in the EXL-50U
Yuejiang 跃江 SHI 石, Xianming 显明 SONG 宋, Dong Guo, Xinchen Jiang, Yong Liu, Xiang Gu, C.S. Liu, Jia Li, Shaodong Song, Yumin Wang, Songjian Li, Ran Tao, Kun Han, L. Y. Dong, Cong Zhang, Yujin LI, Tiantian Sun, Fan Gao, Yifei Zhao, Yupeng Zhang, Qi Wu, Yu Yan, Lei Li, Guang Yang, Xianli Huang, He Hongming, Dong Li, Huasheng Xie, Bing Liu, Han-yue Zhao, Enwu YANG, Yuanming Yang, Yu Wang, Lei Han, Bo Xing, Zhenxing Wang, Pan Zhou, Wei Luo, Chao Wu, Xin Zhao, Chen Bian, Wu Kun, Y. Liang, Jiaqi Dong, B.S. Yuan, Y-K Martin 元凯 PENG 彭, Minsheng Liu, the TCV Team
Abstract
Abstract One mega ampere (MA) plasma discharges were achieved in the EXL-50U spherical torus (ST) in hydrogen–boron (p–B) plasmas with toroidal fields of up to 1 T at major radii of up to 0.6 m. A key innovation in these experiments was the use of a boron-rich fueling strategy incorporating a high-concentration boron-containing gas mixture and real-time boron powder injection during the discharges. The boron content in the fuel reached 10%, representing the first publicly reported MA-class p–B plasma with such a high boron concentration. Noninductive plasma startup was achieved using electron cyclotron resonance heating (ECRH), and a rapid current ramp-up to 1 MA was realized through the synergistic use of ECRH and the central solenoid (CS). At 800 kW of ECRH power, core electron temperatures of up to 3 keV were attained. These results demonstrate the feasibility of producing high-performance p–B plasmas in a spherical torus configuration and offer important physics and engineering insights for future reactor-scale applications—particularly in the areas of current start-up at low loop voltage and real-time boronization techniques.