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

to compensate for electron losses is not very good and thus the zones
will disappear for relatively small values of h/l. However, in the opposite
case for a material with a large SEY, like e.g. aluminium, multipactor
will be possible also for relatively thin irises.
4.3 Comparison with experiments
By comparing the current model with experimental data [61], good qualitative
agreement can be observed (see Fig. 4.5). As the h/l-ratio increases,
the threshold increases until, beyond a certain limit, no multipactor
is possible. Since only the electron losses due to the random drift
are accounted for, the model predicts the existence of a discharge beyond
the limit found in the experiments. Consequently, from an engineering
point of view, this is a conservative measure of the increased threshold
and thus it should be safe to apply it when designing multipactor free
microwave hardware.
Peak Voltage [V]
3500
3000
2500
2000
1500
Multipactor in iris
1000
Current model a)
Current model b)
Current model c)
Current model d)
Measur. −presentation
Measur. −proceedings
500
0 1 2 3 4
Height/Width [−]
5 6 7 8
Figure 4.5: The multipactor threshold as a function of h/l for different parameters
of the current model. For comparison, measurement
data from [51] is included. Parameters used in a): h = 1.2 mm,
f = 9.56 GHz, WT = 2 eV, W0 = 2 eV, W1 = 59.1 eV, and
σse,max = 2.22, (i.e. W1 = Wf2 and σse,max = αmax in table A-6
for silver in [50])). Modified parameters in: b) W0 = WT = 4 eV,
c) W1 = 40 eV, and d) W1 = 80 eV.
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