Abstract: In the C-2 field reversed configuration (FRC) experiment, tangential neutral beam injection coupled with electrically-biased plasma guns, magnetic end plugs, and advanced surface conditioning led to dramatic reductions in turbulence driven losses and greatly improved plasma stability. Under such conditions, highly reproducible, macroscopically stable FRCs with a significant fast ion population and total plasma temperature of 1keV were achieved. In order to sustain the FRC, the C-2 device was recently upgraded with a new neutral beam injection (NBI) system, which increased the injected neutral power from 4 MW to 10+ MW, by far the largest ever used in a compact toroidal plasma experiment. The upgraded neutral beams produce a fast ion population that has a dramatic beneficial impact and allows the configuration to persist for time significantly longer (5+ ms) than all characteristic plasma decay times. The presentation with provide an overview of the C-2U device and recent experimental results, with a focus on the diagnosis of the fast ion population
and observations of benign fast ion driven collective effects.