Multipactor in Low Pressure Gas and in ... - of Richard Udiljak

N e /N 0 [−]
3
2.5
2
1.5
1
Multipactor in iris
σ = 1.159
σ = 1.151
0.5
0 50 100
Number of collisions
150 200
Figure 4.3: The growth in electron number as a function of the number of
gap crossings for two different SEY-coefficients. Parameters used:
f = 1 GHz, N = 1, l = 2 mm, and WT = 2 eV.
or equivalently
σse > 1/γ0 > 1. (4.6)
This implies that the secondary electron yield must be greater than a
value that is larger than unity (1/γ0 > 1) to have growth of the number
of electrons. This modified breakdown criterion is the only difference
between the model considered here and the conventional resonance theory
of multipactor inside a plane-parallel gap (where σse > 1 is used
when determining the threshold). The condition for σse, Eq. (4.6), can
be converted into a range of impact energies,
W1 < Wmin < Wimpact < Wmax < W2, (4.7)
where the impact energies Wmin and Wmax are determined by σse =
1/γ0. Consequently, using Wmin and Wmax instead of W1 and W2, respectively,
in the parallel-plate model, multipactor regions that account
for the electron losses due random drift can be obtained.
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