Numerical Model for Extraction of Ions from Plasma

The ion-extraction process is investigated using the numerical model of a plasma ion source. The operating characteristics of the ion-optical system, such as the dependence of the plasma meniscus surface and the ion current on the extraction voltage, are found. In particular, it is shown that the ion current-extraction voltage characteristic is represented by the expression I = AU 3/4, which differs from the well-known Child-Langmuir formula. Some new characteristics of the ion-optical system—its dynamic perveance and effective emitting area—are introduced.