Biomedical Engineering Reference
In-Depth Information
Fig. 3
Optimized plasma
chamber design with
reduced side gaps,
optimized electrode
surface ratio and without
bottom metallization
Fig. 4
Simulated electron trajectories between plasma and ionization chamber
The potential difference in this region and therewith the extension of the sheath for
not too different electrode areas can be approximated by [
15-
17
] :
4
⎛⎞
=
⎜⎟
⎝⎠
U
A
UA
1
2
.
2
1
The sheath potential is minimized, when the electrode area ratio equals 1. The
design of Fig.
3
fulfills this requirement. The lowest possible pressure, for which a
stable plasma can be established, is 30 Pa.
For this layout of the plasma chamber the trajectories of the electrons as well as the
ions in an applied electrical field were simulated with the SIMION 8.0 software [
18
] .
Figure
4
depicts the extraction of electrons out of the plasma chamber for a potential
difference of 100 V between the plasma and the ionization chamber [
19
] at vacuum
conditions, i.e., without electron-gas interaction. The corresponding electron energy
