ENN's Roadmap for Proton-Boron Fusion Based on Spherical Torus

Energy iNNovation (ENN) Science and Technology Development Co. is committed to generating fusion energy in an environmentally friendly and cost-effective manner, which requires abundant aneutronic fuel. Proton-boron ( p-^11B or p-B) fusion is considered an ideal choice for this purpose. Recent studies have suggested that p-B fusion, although challenging, is feasible based on new cross-section data, provided that a hot ion mode and high wall reflection can be achieved to reduce electron radiation loss. The high beta and good confinement of the spherical torus (ST) make it an ideal candidate for p-B fusion. By utilizing the new spherical torus energy confinement scaling law, a reactor with a major radius R_0=4 m, central magnetic field B_0=6 T, central temperature T_i0=150 keV, plasma current I_p=30 MA, and hot ion mode T_i/T_e=4 can yield p-B fusion with Q>10. A roadmap for p-B fusion has been developed, with the next-generation device named EHL-2. EHL stands for ENN He-Long, which literally means "peaceful Chinese dragon". The main target parameters include R_0≃1.05 m, A≃1.85, B_0≃3 T, T_i0≃30 keV, I_p≃3 MA, and T_i/T_e≥2. The existing ST device EXL-50 was simultaneously upgraded to provide experimental support for the new roadmap, involving the installation and upgrading of the central solenoid, vacuum chamber, and magnetic systems. The construction of the upgraded ST fusion device, EXL-50U, was completed at the end of 2023, and it achieved its first plasma in January 2024. The construction of EHL-2 is estimated to be completed by 2026.