[en] Two dimensional electrostatic particle simulation is implemented to study potential formation in the system including the magnetic filter and the plasma grid. In the case of uniform density and temperature profile, the plasma grid can not locally control the plasma potential. In the case of nonuniform profile in which the magnetic filter separates the plasma into high density and high temperature (source plasma) and low density and low temperature (diffused plasma) regions, plasma potential is high in the source plasma region and low in the diffused plasma region. It is possible that plasma potential in the diffused plasma is locally controlled by changing plasma grid potential. (author)