Influence of work function on the multipactor threshold

Abstract

The multipactor effect is characterized by a very fast growth of the electronic population in vacuum Radio-Frequency (RF) devices. As it limits the transmitted RF power and can severely damage RF systems, multipactor has been subject to an extensive research for the past decades. Simulation tools are relatively accurate for the simplest cases, but less reliable for advanced problems: presence of an external magnetic field, complex geometry, time or temperature-dependent materials properties, etc. A code simulating the multipactor within an infinite parallelplate waveguide with a dielectric coating on the bottom plate has been developed. The inclusion of a realistic energy distribution for the secondary electrons and a new emission model shows a strong dependence of the multipactor threshold on the metal work function and on the dielectric electric charge.

A numerical and theoretical study of the multipactor appearance in the presence of a DC parallel electric field

“…We inject these phases in Eq. (5a) to compute the TEEY of each collision and verify if (11) is fulfilled. If it is not, E 0 is incremented.…”

“…It is possible to simulate configurations involving dielectric materials and/or magnetic fields. 11,12 Ne seed electrons are injected in the waveguide during the three first signal periods. The simulation is carried on for up to 60 000 periods.…”

A three-dimensional Dionne model for multipactor simulations

“…Preliminary multipactor simulations have been made with the simulation code POTOMAC (Physical simulatiOn TOol for Multipactor in Advanced Configurations) [11][12][13] . POTOMAC is a PIC code that computes the evolution of the electron population in a domain with a given RF electric field.…”

“…All terms in the Dionne model have a physical meaning. Thus, it is for example possible to analytically reflect the influence thin coatings have on the SEEY and hence on the multipactor 12,35 . However, Dionne's model does not take into account for the incidence angle of the PE, unlike Vaughan.…”

POTOMAC: Towards a Realistic Secondary and Backscattered Emission Model for the Multipactor

“…All the constitutive terms of this model have a physical sense. It is for example possible to modify in order to take into account for the presence of thin layers on top of the materials [13], [14] or to consider the influence of dielectrics charge [15]. However, this model does not take into account the incidence angle of PE, which is mandatory to work with magnetic fields among others.…”