The electron cloud populated by a multipactor within two emissive parallel plates was modeled by two thin sheets of charge, and for the first time the equations of the particle motion for this two-sheet system were derived taking into account space charge effects. The electron population growth in multipacting process was then simulated with the code developed on the base of these equations. It was found that the mutual repulsion between the sheets, i.e., space charge effects, results in the increasing of charge in one of the sheets and the loss of charge in the other due to the different growth rates. This process eventually comes to the saturation of one sheet and the dissappearence of the other.

Multipactor breakdown is studied inside the capacitive iris of a rectangular waveguide with a skewed slot along its longitudinal cross section. Both the iris length and height are assumed to be small compared to the electromagnetic wavelength. Therefore, the quasi-static approximation is applied so as to describe the RF field distribution inside the iris gap, whereas a 2-D model is used to analyze the electron motion. The peculiarities of RF field structure are studied using the conformal mapping approach, which shows that the electric field lines can be approximated by circular arcs when the iris length is much larger than its height. The electron motion inside the iris gap is analyzed using different analytical approaches as well as numerical simulations. The simplest analytical consideration is based on the general theory of multipactor between curved surfaces. Within the more sophisticated model, the fringing field effect on electron motion inside the iris is calculated assuming circular structure of electric field lines. It is demonstrated within all approaches that the electron losses within the iris gap increase considerably with the skew angle, deviating from the rectangular iris shape. As a result, the multipactor becomes impossible at a relatively small value of this angle.

Secondary electron emission has an important role on the triggering of the multipactor effect; therefore, its study and characterization are essential in radio-frequency waveguide applications. In this paper, we propose a theoretical model, based on equivalent circuit models, to properly understand charging and discharging processes that occur in dielectric samples under electron irradiation for secondary electron emission characterization. Experimental results obtained for Pt, Si, GaS, and Teflon samples are presented to verify the accuracy of the proposed model. Good agreement between theory and experiments has been found.

An analytical study of the electron trajectories between two opposite electrodes having curved surfaces is undertaken for the case when the electron transit time exceeds the RF period. The analysis is based on a statistical approach, which makes it possible to calculate the width of an electron bunch after a number of electron transits taking into account the spread of electron emission velocity, and the spatial nonuniformity of the RF field using the concept of the ponderomotive force. The results are used to estimate the multipactor threshold in terms of a value of the secondary emission yield, which is necessary to balance electron losses. Based on the model, it is predicted that multipactor is impossible inside the realistic configuration of a helix antenna where four electrodes are placed on the same cylindrical surface.

This paper deals with the analysis of the Multipactor effect in RF components with ferrites performed through the preliminary measurements of ferrites secondary emission coefficient and the simulations of the effect of a continuous magnetic field on the electron bunch spread. The impact of this effect on the Multipactor threshold was quantified.

New generation telecommunications satellites are designed to cater for constantly increasing number of users, asking for higher and higher bit rates, in the same frequency multiplex. The combination of these two tendencies implies increasing power levels in the RF equipment downstream from the power amplifiers. In this situation, different types of discharge phenomena can occur inside the microwave devices. The consequences may be link budget degradation or even damage to the equipment. Two kinds of discharges can occur depending on the pressure range:

Simulations have been performed to determine the multipactor breakdown threshold in a microwave structure composed of two parallel cylinders, chosen to be an approximate model of an open helix microwave antenna system. The electromagnetic field between the cylinders is available in closed analytical form, and a Monte Carlo software has been developed to calculate the 2-D electron trajectories and to simulate the multipactor avalanche in this inhomogeneous electric field for different ratios of cylinder radius and distance of separation between the cylinders. The results are compared with those of a recently published analytical theory and show a qualitatively good agreement. In particular, it is confirmed that, for a given distance between cylinders, there exists a smallest cylinder radius below which no two-sided multipactor breakdown can occur. The basic physical explanation is a loss mechanism for secondary emitted electrons that is caused by the curvature of the cylinder surfaces together with the strong electric field at the surfaces. The results imply that the breakdown threshold in realistic open helix antennas is significantly higher than those predicted using extrapolations based on resonance theory and the classical two parallel plate model.

Multipactor breakdown is a serious risk in all types of high power microwave equipment working in low pressure or vacuum environments. This is especially pronounced in the case of RF devices intended for operation in space, due to the limited testing ability, the high costs involved, and the near impossibility of repairing a system in orbit. This motivates the need for theoretical predictions and good design guidelines. Most studies of the multipactor breakdown mechanism have considered relatively simple geometries, where the field is homogeneous, surfaces are flat, and the only way that electrons are lost is through absorption by the conductive walls. We investigate the basic mechanisms of the multipactor breakdown phenomena in a quadri-filar helix antenna (QFHA). The ECSS specifies the parallel plates model to be used for breakdown threshold estimates, but in contrast to the parallel plates, the helix system is characterized by an inhomogeneous field profile, curved surfaces, and an open geometry. Since the full system is too complicated to yield to theoretical analysis in the first instance, a simplified geometry in the form of two infinite parallel cylinders was chosen to represent the system. This choice can be justified due to the low pitch angle and long lengths (in terms of wavelength) of typical QFHA:s. We develop a model which takes into account the electron density dilution due to the curved surfaces, the random arrival phase of electrons, and the ponderomotive force, which tends to push electrons out of high field areas. The resulting lower breakdown voltage estimates show a strong dependence on cylinder radii, where double sided multipactor below certain radii becomes impossible. Monte Carlo simulations of the two wire system, taking into account the full electron dynamics, have been performed for different cylinder separations. The theoretical predictions and simulations show good agreement, and seem to provide a clear improvement compared to those corresponding to the parallel plates model.