2-DIMENSIONAL FLUID SIMULATION OF EXPANDING PLASMA SHEATHS

The transient sheath expansion around square and cross-shaped targets is simulated numerically with a two-dimensional fluid model. The angul ar distribution of the ions impinging on the target surface and the no nuniformity of the incident ion dose are calculated. The incident ion dose peaks near, but not at, the convex corner and has a minimum at th e concave corner. The dip of the dose profile at the convex corner is shown to be caused by the product of a decreasing normal velocity prof ile and an increasing ion density profile along the target surface fro m the center to the corner. (C) 1995 American Institute of Physics.