6
Theory of Operation
The function of an ion beam source is to produce ions and accelerate these ions to high velocities so
they are ejected downstream from the source. The ejected ions are directed to form a “beam” in
which the ions are mono-energetic with velocities on the order of km/s. An ion beam source
consists of four (4) key elements:
Discharge Chamber, Electron Source, Grids, and Neutralizer
Presented in Figure 2.1 is a schematic of an ion beam source. Basically, the source is operated by
introducing the source gas into the
discharge chamber
. An
electron source
is used to ionize the
gas and establish a plasma. Recall, a plasma is an electrically conductive gas where the density of
ions and electrons are approximately equal. Ions created in the
discharge chamber
are then
accelerated to high velocities with the source
grids
. A
neutralizer
is placed downstream from the
source where it emits electrons to balance the number of positive ions which leave the source.
Figure 2.1: Schematic of an ion beam source.
Chapter
2