Time Evolution of the Magnetic Structure of a Field-Reversed Configuration in a Super-Alfvénic Translation Process

Abstract

The effects of the conducting wall on the FRC translation process have been investigated by using a confinement coil with a toroidal cut on the coil spool. Using the simple ring current model, the induced current on the conducting coil spool and chamber wall, and the separatrix shape, were estimated. A deceleration force produced by the induced currents equals to approximately 10% of the acceleration one generated by the gradient of the magnetic guide field. To investigate these effects experimentally, FRC translation was performed with a toroidal cut on the coil spool. In this case, typical translation velocity was increased from 100 to 150 km/s. However, a shift type (toroidal mode number n = 1) motion was triggered, likely by the asymmetry of the wall boundary.