As in other plasma devices with a curved magnetic field geometry, an asymmetric density profile is observed in the PLADEPUS, a toroidal plasma source, at the University of Sydney. In this letter, we demonstrate that the asymmetric density profile can be improved by means of a positive bias electric field at the edge of the plasma. With the bias field, the density profile becomes symmetric and broadened, and the plasma density is enhanced. ©1997 American Institute of Physics.