Achieving a long-lived high-beta plasma state by energetic beam injection

Developing a stable plasma state with high-beta (ratio of plasma to magnetic pressures) is of critical importance for an economic magnetic fusion reactor. At the forefront of this endeavour is the field-reversed configuration. Here we demonstrate the kinetic stabilizing effect of fast ions on a disruptive magneto-hydrodynamic instability, known as a tilt mode, which poses a central obstacle to further field-reversed configuration development, by energetic beam injection. This technique, combined with the synergistic effect of active plasma boundary control, enables a fully stable ultra-high-beta (approaching 100%) plasma with a long lifetime. A stable plasma state with a high ratio of plasma to magnetic pressures is likely to be a key requirement for any future magnetic fusion reactor. Here, the authors create such a plasma using a field reversed configuration and active plasma boundary control and demonstrate its stability.