Effect of plasma inhomogeneity on grid performance

In broad-beam ion sources an inhomogeneous plasma distribution has a strong effect on the maximum extractable ion current, the broad-beam profile and the grid lifetime. Two methods for the determination of the plasma density profile at the sheath are described and tested with two ion sources of diff erent size and plasma excitation mode. It is demonstrated that the descript ion of the broad-beam profiles can be significantly improved by taking into account the plasma profile. (C) 2001 Elsevier Science B.V. All rights rese rved.