Optimization of poloidal field system and advanced divertor equilibrium configuration design of EHL-2 spherical torus
Year: 2026
Type: article
Abstract: The ENN He-Long 2 (EHL-2) project aims to achieve and validate the p– 11 B thermal fusion reaction by establishing a high-ion-temperature scenario plasma regime and developing the necessary physics and engineering foundation for next-generation spherical torus (ST). This study presents an improved equilibrium configuration and poloidal field (PF) system design for EHL-2, focusing on achieving stable X-point target (XPT) operation under stringent thermal and structural constraints. A self-consistent iterative framework integrating equilibrium, transport, and waveform design was developed to ensure physical feasibility and engineering robustness. To enhance XPT stability, the secondary X-point was repositioned out of the horizontal extent of central solenoid (CS) coil, and the divertor-coil cross-sectional areas were enlarged to mitigate excessive rise in temperature. The resulting PF system, comprising a CS coil and 12 PF coils, supports high-ion-temperature scenario. The equilibrium optimization, based on a high-ion-temperature scenario current profile, revealed strong bootstrap currents near the plasma edge that sustain high elongation and equilibrium stability. Validated waveforms were derived with Shape Editor, ensuring compliance with voltage-second balance, vertical stability, and thermal limits across all waveform phases. Furthermore, the feasibility of the fishtail divertor concept was explored through periodic modulation of selected PF coils, demonstrating its potential for dynamic strike-point sweeping and improved heat-load management. These results collectively provide a comprehensive design framework for achieving stable, high-performance operation in the EHL-2 ST, advancing the pathway toward compact, high-temperature fusion reactors.
Source: Plasma Science and Technology
Authors: Xiang 翔 GU 顾, Xianming 显明 SONG 宋, Wenjun LIU (刘文军), Jiankun HUA (华建坤), Xueyun WANG (王雪韵), Xiao SONG (宋啸), Yuejiang SHI (石跃江), Lili DONG (董力立), Yuanjing AN (安苑静), Shuo LIU (刘硕), Yu WANG (王宇), Hong ZANG (臧红), Xiaokun BO (薄晓坤), Yuanming YANG (杨圆明), Jiaqi 家齐 DONG 董, Yueng-Kay Martin 元凯 PENG 彭, Baoshan YUAN (袁保山), Yunfeng 云峰 LIANG 梁, the EHL-2 Team
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W7204034183