Multipactor suppression in amplitude modulated radio frequency fields

An analytical and numerical investigation is made of the multipactor phenomenon in a simple one-dimensional metallic gap exposed to a homogeneous rf field consisting of two carrier waves with close but separated frequencies. It is shown that in contrast to the monochromatic case (i.e., single carrier operation), the time varying envelope resulting from the beating of the two carrier waves leads to a suppression of multipactor breakdown, if appropriate combinations of carrier amplitudes and frequency separation are chosen. Furthermore, this combination depends neither on gap width nor on frequency range. Based on these results it is possible to draw the tentative conclusion that the regime of multicarrier operation is very promising from the point of view of avoiding breakdown. This is particularly so in systems of complicated geometry where single carrier operation may lead to multipactor breakdown for any high level of rf power.