Compact Plasma and Focused Ion Beams

130 Compact Plasma and Focused Ion Beams

A trigger signal, Trig, was used for pulse initiation and as a reference signal

for diagnostics. A personal computer (PC) was used for storing data. The cur-

rent decay proles and probe characteristics were measured by a Langmuir

probe P (plane, 5 mm

ϕ

) using a digital oscilloscope DSO with time averaging

(64 sots) and a Boxcar integrator BX. For measuring the decay proles of ion

(I

+

) and electron currents (I

e

), the probe was biased at −70 and 20 V, respectively.

For obtaining the probe characteristics using the Boxcar integrator, the

gate aperture was set at 0.1 μs and the decay to 30–50 μs, measured ...