Multipactor in rectangular waveguides

Abstract

Multipactor inside a rectangular waveguide is studied using both an analytical approach and numerical simulations. Particular attention is given to an analysis of the role of such effects as the velocity spread of secondary emitted electrons and the action of the rf magnetic field on the electron motion. Conventional resonance theory is shown to give correct predictions for the multipactor threshold in cases where the height of the waveguide is very small and first order resonance multipactor dominates. In cases of higher order resonances, an accurate prediction of the multipactor threshold requires that the spread of the normal component of the electron emission velocity is taken into account. Furthermore, the spread of the tangential component of the electron emission velocity and the action of the rf magnetic field are shown to be very important when the waveguide height exceeds a certain critical value, which depends on the waveguide width. A new theory is developed for predicting the multipactor threshold at higher order resonances and this theory is confirmed by numerical simulations.

Simulations of multipactor in circular waveguides

“…These results make it possible to conclude that in the case of linear polarization, the considered seed electrons cross the waveguide whereas in the case of circular polarization, the electrons return to the surface of emission. This electron behavior is caused by the repulsive action of the Miller force, 14,33 which is stronger in the case of circular polarization as is clear from the distribution of the microwave field intensity along the axis shown in Fig. 5.…”

“…This is due to two reasons: a single transit of an electron between the walls of the waveguide takes long time ͑about 50 microwave periods or even more͒ and the establishing of the electron avalanche requires many consecutive electron transits. Previously the same problem was met in simulations of the multipactor in rectangular waveguides 14 and microstrip lines. 17 As emphasized in these papers, Monte Carlo simulations of the long time evolution of the multipactor discharge must be very accurate and in order to suppress statistical fluctuations it is necessary to consider a very large number of electron trajectories.…”

“…This type of discharge is an undesirable phenomenon in many practical microwave applications and the intense study of this phenomenon during the last decades has mainly been stimulated by the necessity to be able to accurately predict the multipactor threshold in different microwave subsystems. [1][2][3][4][5] These studies have resulted in development of various numerical tools capable of simulating multipactor in different geometries including parallel plates, 6,7 coaxial cables, [8][9][10] dielectric windows, [11][12][13] rectangular and wedge-shaped waveguides, [14][15][16] microstrip lines, 17 waveguide irises, [18][19][20] and rf filters and transformers. [21][22][23] A notable exception is multipactor breakdown in circular waveguides, which has been given scant interest, in spite of its technical importance.…”

Multipactor Breakdown in Elliptical Waveguide Carrying Orthogonal Polarizations

“…Thus, a number of microwave structures have been studied during last years in the technical literature. In these studies, the effective electron method has been used to obtain the RF breakdown threshold for several components including rectangular waveguides [15], coaxial transmission lines [16,17], circular waveguides [18,19], microstrip lines [20], wedge-shaped rectangular guides [21,22], elliptical waveguides [23,24], and dielectric resonator waveguide filters [25]. The details of this technique have been extensively reported in [14] and [22], which basically includes the simultaneous tracking of the finite number of effective electrons trajectories.…”

Non-resonant multipactor—A statistical model

“…Only in a few cases [5][6][7][8][9][10][11][12][13][14] can the problem be treated analytically. This has motivated the wide use of numerical simulations, both particle-in-cell (PIC) and Monte Carlo, to calculate the breakdown thresholds and study the electron trajectories.…”