Overview of the physics design of the EHL-2 spherical torus
Y. Liang, Huasheng Xie, Yuejiang Shi, Xiang Gu, xinchen Jiang, Lili Dong, Xueyun Wang, Danke Yang, Wenjun 文军 LIU 刘, Tiantian Sun, Yumin Wang, Z. Li, Jianqing Cai, Xianming Song, Muzhi Tan, Guang Yang, Hanyue Zhao, H. Ma, Yueng-Kay Martin 元凯 PENG 彭, Shaodong 绍栋 SONG 宋, Zhengyuan 正元 CHEN 陈, Yingying 颖颖 LI 李, Yingying Li, Di 迪 LUO 罗, Yuanming 圆明 YANG 杨, Minsheng 敏胜 LIU 刘, the EHL-2 Team
Abstract
Abstract ENN is planning the next generation experimental device EHL-2 with the goal to verify the thermal reaction rates of p- 11 B fusion, establish spherical torus/tokamak experimental scaling laws at 10’s keV ion temperature, and provide a design basis for subsequent experiments to test and realize the p- 11 B fusion burning plasma. Based on 0-dimensional (0-D) system design and 1.5-dimensional transport modelling analyses, the main target parameters of EHL-2 have been basically determined, including the plasma major radius, R 0 , of 1.05 m, the aspect ratio, A , of 1.85, the maximum central toroidal magnetic field strength, B 0 , of 3 T, and the plasma toroidal current, I p , of 3 MA. The main heating system will be the neutral beam injection at a total power of 17 MW. In addition, 6 MW of electron cyclotron resonance heating will serve as the main means of local current drive and MHD instabilities control. The physics design of EHL-2 is focused on addressing three main operating scenarios, i.e., (1) high ion temperature scenario, (2) high-performance steady-state scenario and (3) high triple product scenario. Each scenario will integrate solutions to different important issues, including equilibrium configuration, heating and current drive, confinement and transport, MHD instability, p- 11 B fusion reaction, plasma-wall interactions, etc. Beyond that, there are several unique and significant challenges to address, including establish a plasma with extremely high core ion temperature ( T i,0 > 30 keV), and ensure a large ion-to-electron temperature ratio ( T i,0 / T e,0 > 2), and a boron concentration of 10%‒15% at the plasma core; realize the start-up by non-inductive current drive and the rise of MA-level plasma toroidal current. This is because the volt-seconds that the central solenoid of the ST can provide are very limited; achieve divertor heat and particle fluxes control including complete detachment under high P / R (> 20 MW/m) at relatively low electron densities. This overview will introduce the advanced progress in the physics design of EHL-2.