Compact Plasma and Focused Ion Beams

278 Compact Plasma and Focused Ion Beams

start of the pulse, t = 0), depending upon the pressure, which is in conformity

to earlier experimental results with shorter-duration pulses.

From the electron plasma oscillations, as shown in the inset of Figure 17.2a,

an exponential decay factor

α

is obtained by considering the peak ampli-

tude of the waves. Figure 17.3 shows that

α

increases with pressure, indicat-

ing that electron–neutral collisions play an important role in damping these

waves. The growth rate

β

of the electron current after the end of the plasma

wave is estimated to be of the order of 10

5

s

−1

, as shown in Figure 17.3, and

increases ...