  In a new toroidal laboratory plasma device including a poloidal magnetic
field created by an internal circular conductor, the confinement efficiency of
the magnetized plasma and the turbulence level are studied in different
situations. The plasma density is greatly enhanced when a sufficient poloidal
magnetic field is established. Moreover, the instabilities and the turbulence
usually found in toroidal devices without shear of the magnetic field lines are
suppressed when the rotational transform is present. The measurement of the
plasma decay time allows to determine the confinement time of the particles
which is compared to the Bohm diffusion time and to the value predicted by
different diffusion models, especially the neoclassical diffusion.
