
56 Compact Plasma and Focused Ion Beams
The electrons gain energy from the waves until the energy growth starts
to saturate, as it crosses the elastic limit and inelastic collisions start to domi-
nate. During the course of its motion, the electron satises any one of the loss
criterion described below. The electrons may gain energy and
a. Escape from the volume purely by elastic collisions.
b. They may undergo inelastic collisions after traveling a certain dis-
tance, in the volume determined by r <
Λ
.
In case (a), the electrons escape from the volume purely by elastic colli-
sions, and the variation of N with
Λ
/
λ
is readily obtained. In case ...