Translation of Field-Reversed Configuration into a Confinement Region Filled with Neutral Gas

The effects of the background particles on the translation process have been investigated by NUCTE-III and the newly upgraded NUCTE-III/T devices. In NUCTE-III experiments, field-reversed configuration (FRC) plasmas are translated into weakly ionized plasma with translation velocity of 100km/s. The decay time of the particle inventory and the poloidal flux were prolonged in the experiments. The relative motion between translated FRC and background particles can be assumed to be equivalent to axially injected warm neutral beam. In this point of view, particle simulation under the experimental conditions has also been performed to investigate the effects of the injected particles. The equivalent beam injection with higher injection energy can supply not only the particle inventory but also the kinetic energy into the target FRC plasma. To clarify the second effects of the above, the experimental device has been upgraded. This realizes higher injection velocity up to 150km/s and controllable background gas density. The confinement properties with NUCTE-III/T experiments have been observed to be similar to the initial experiments on NUCTE-III.