Compact Plasma and Focused Ion Beams

153Plasma Production in Pulsed-Mode Microwaves

Figure 9.12 shows the temporal variation of the space potential V

s

as deter-

mined by Equation 9.2 at some pressures measured at z = 2 cm. It is noted

that V

s

has a higher value during the initial stages and gradually decreases

with time. At lower pressures (e.g., 0.06 and 0.1 Torr), the slope dV

s

/dt is larger

and the plasma seems to reach the potential equilibrium more quickly.

The temporal variation of the electron temperature T

e

determined from the

probe characteristics shows a value of about 6–10 eV for at least a few tens

of microseconds after the end of the microwave pulse. At a time close to ...