In order to restore the plasma stability in the Heliotron C magnetic field, the Heliotron-P field, which has buried ring conductors inside the vacuum vessel and thus avoids the cusp losses, has been proposed. As a preliminary experiment on the plasma confinement in this field, the plasma behaviour in a mirror field having a current carrying ring conductor, which corresponds to the one section of the Heliotron-P field, is investigated. The plasma injected from a gun into this field rapidly fills up the region near the separatrix showing the existence of the magnetic well. The plasma ( Tₑ≃20 eV, Tₑ≤11 eV, n?10¹1) is stably confined in this field. The predominant loss is the mirror end loss, and the net radial loss time is inferred to be 1.4 msec. Drift instability is observed only in the region of the steep density gradient at the plasma periphery
