CEST and MEST: Tools for the simulation of radio frequency electric discharges in waveguides

Abstract

Esta es la versión de autor del artículo publicado en: This is an author produced version of a paper published in: AbstractIn this paper we present two software tools for the simulation of electron multiplication processes in radio frequency (RF) waveguides. The electric discharges are caused by the multiplication of a small initial number of electrons. These are accelerated by the RF field and produce new electrons either by collisions with the walls of the waveguide (ripping new electrons from them), or by ionization of the neutral atoms of a gas inside the device.MEST allows simulating the Multipactor effect, a discharge produced in vacuum and generated by the collision of the electrons with the walls. CEST simulates the discharge when in addition a neutral gas is present in the waveguide, at pressures lower than ground levels (often denominated Corona discharge). The main characteristic of both tools is that they implement individual-based, microscopic models, where every electron is individually represented and tracked. In the case of MEST, the simulation is discreteevent, as the trajectory of each electron can be computed analytically. In CEST we use a hybrid simulation approach. The trajectory of each electron is governed by the Langevin stochastic differential equations that take into account a deterministic RF electric force and the random interaction with the neutral atom background. In addition, wall and ionizing collisions are modelled as discrete events.The tools allow performing batches of simulations with different wall coating materials and gases, and have produced results in good agreement with experimental and theoretical data. The different output forms generated at run-time have proven to be very useful in order to analyse the different discharge processes. The tools are valuable for the selection of the most promising coating materials for the construction of the waveguide, as well as for the identification of safe operating parameters.

Influence of secondary emission yield on the saturation properties of multipactor discharges between two parallel metal plates

“…Accurate predictions of the conditions under which a multipactor discharge may occur are therefore a necessary stage in the design of microwave components. [3][4][5][6][7][8] For realistic device geometries, such predictions must be based on numerical simulations. Unfortunately, the secondary emission properties of the device walls are sensitive to contamination of the solid surface and even numerical simulations cannot guarantee multipactor free operation of a device.…”

Advanced Techniques for Multipactor Testing

“…Although there have been published multipactor analysis codes for specific geometries such as rectangular waveguide [60], circular waveguide [60], elliptical waveguide [61] or coaxial [60,52,38,39,62], commercial tools tend to be generic and to allow random geometries, multiple materials or different models for the secondary emission physics. From the signal excitation point of view, they may allow multicarrier or modulated signals and, in some cases, they also take into account the electron-to-electron interaction [63].…”