Multipactor saturation in parallel-plate waveguides

Abstract

The saturation stage of a multipactor discharge is considered of interest, since it can guide towards a criterion to assess the multipactor onset. The electron cloud under multipactor regime within a parallel-plate waveguide is modeled by a thin continuous distribution of charge and the equations of motion are calculated taking into account the space charge effects. The saturation is identified by the interaction of the electron cloud with its image charge. The stability of the electron population growth is analyzed and two mechanisms of saturation to explain the steady-state multipactor for voltages near above the threshold onset are identified. The impact energy in the collision against the metal plates decreases during the electron population growth due to the attraction of the electron sheet on the image through the initial plate. When this growth remains stable till the impact energy reaches the first cross-over point, the electron surface density tends to a constant value. When the stability is broken before reaching the first cross-over point the surface charge density oscillates chaotically bounded within a certain range. In this case, an expression to calculate the maximum electron surface charge density is found whose predictions agree with the simulations when the voltage is not too high. V C 2012 American Institute of Physics.

Engineered surfaces to control secondary electron emission for multipactor suppression

“…The seed electron can originate from a variety of sources including field emission or photoelectric emission from a sidewall, electrons native to the space environment, or an electron cascade produced by a cosmic ray. 5,6 Fig. 1.…”

“…3 The primary scientific and engineering communities concerned with multipactor are those involved with vacuum electronic devices (VEDs), space-based systems, and particle accelerators. 5…”

Simple model of the rf noise generated by multipacting electrons

“…It should be noted that the solution of any specific problem depends on the entire rf circuit, which controls not only the radiation power of any given electric current but also governs the multipactor saturation stage. Actually, it is generally recognized that within the plane-parallel model, multipactor saturation is caused mainly by the space charge effect, which can change the electron motion considerably (for example a two-surface multipactor can be transformed into a single-surface multipactor [3][4][5][6][7]). However, in cases where the rf circuit contains one or more resonant cavities (which is a typical situation for any rf filter or transformer), multipactor saturation is caused mainly by impedance mismatch which results in a reduction of the rf voltage amplitude down to the multipactor threshold value [4,8].…”

“…where 1  k , and 1 J denotes the spectral amplitude of the first harmonic of the current, which is the same as that given in equation (7). In contrast to multipactor with a single electron sheet, when all possible electron sheets have the same number of electrons the effective electric current, J , contains only integer odd harmonics of the applied electric field (see Fig.…”

Simulation of Multipacting with Space Charge Effect

“…It is shown in [4,5,6,7] that the space charge effect plays a prominent part in the secondary electron resonance discharge, i.e. multipacting.…”