Dynamic property of spontaneous toroidal field in field-reversed configuration plasmas

The toroidal field in the translated field-reversed configuration (FRC) plasma has been measured, although the FRC plasma has sometimes been described as having only the poloidal field. Measurements of the toroidal field distribution during the plasma translation clarify the location where the toroidal field originates. The experimental results show that the flux of poloidal and toroidal components decays monotonically in time after the beginning of the translation. This indicates that the toroidal field occurs just after the FRC formation without further production during the translation.