Increased p- 11 B fusion reaction rate through fast-ion acceleration by ion cyclotron range of frequencies heating in LHD

Abstract Proton-boron-11 (p- 11 B) fusion is an attractive concept for advanced fusion energy because of its nearly aneutronic characteristics. However, efficient use of beam-injected fast ions may be limited by their slowing down through Coulomb collisions, which lead to lower fusion reactivity. In this study we investigate whether ion cyclotron range of frequencies (ICRFs) heating can ameliorate this effect by resonantly accelerating fast ions in the Large Helical Device of a stellarator. Using the tangential neutral beam (NB) injection to supply energetic protons at ∼160–170 keV, together with boron seeding, we conducted a series of experiments with superimposed hydrogen minority ICRF heating for beam proton acceleration. Three complementary experimental methods, ICRF power modulation, NB termination, and NB energy scan, consistently showed that ICRF waves accelerate beam ions and enhance the p- 11 B fusion yield. This led to measurable enhancements in the p- 11 B fusion alpha-particle yield, as observed with a dedicated fusion-product detector. These findings provide the first direct experimental evidence that ICRF heating can improve the efficiency of beam-driven p- 11 B fusion reactions.