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

allows for another design margin, which is set with respect to the so
called P20 power level. The P20 level corresponds to the “peak power of
the multicarrier waveform whose width at the single carrier multipaction
threshold is equal to the time taken for the electrons to cross the multipacting
region 20 times” [50]. This level is illustrated in Fig. 2.15.
Figure 2.15: An example where the in-phase peak power is above the single
carrier threshold, while the P20 level is more than 4 dB below the
same threshold. The peak voltage is 128.4 V, the single carrier
threshold is 91 V, and the P20 voltage is 57 V. Signal data: 12
carriers, equally spaced, fmin = 1.545 GHz, ∆f = 24 MHz and
each carrier amplitude is 10.7 V. Material properties: W1 =
23 eV and σse,max = 3.
In the case when a design is made with respect to the P20 level, the
design margins range from 4-6 dB depending on the type of testing. A
problem with the P20 level is that it is not a trivial problem to find the
peak power level for 20 electron gap crossings. This power level is usually
referred to as the worst case scenario, even though it may not always be
the worst case from a multipactor point of view. A number of different
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