Environmental Engineering Reference
In-Depth Information
Figure 3.1
Electron drift velocity in helium depending on the reduced electric field strength in
the regime of low electron number density according to experiments reported in [32].
Figure 3.2
Electron drift velocity in argon depending on the reduced electric field strength in the
regime of low electron number density according to experiments reported in [32].
where
is the energy of a test electron,
T
is the gas temperature, and
T
e
is the
electron temperature (or the effective electron temperature), which relates to the
particle distribution function for electrons. In particular, if we consider a gas of
helium ionized with
T
ε
7 and the electron energy
corresponds to the excitation threshold of the helium atom
D
400 K,
T
e
D
2eV,andln
Λ
D
ε
D
20 eV, for which
σ
ea
D
6Å
2
, we obtain the following criterion:
N
e
N
a
10
6
3
.
