Abstract: A plasma gun is described which is capable of creating and directing a plasma towards a neutralizing plate. The plate is comprised of a material which is chemically inert, metallic, and whose atoms are substantially heavier than the atoms of the plasma gas. The plasma, upon impacting the neutralizing plate, picks up sufficient electrons to cause the ions to revert to their neutral state. The particles, upon hitting the neutralizing plate, are redirected towards a substrate whose surface is to be altered or eroded. A potential may be applied to the neutralizing plate to enable the energy of the reflected particles to be controlled. The neutral atoms, so redirected, provide a desired anisotropic erosion capability.