Significant Reduction of Multipactor Effect in a Rectangular Waveguide with Periodically Grooved Metallic Surfaces
Angela Coves,Sarah Bonte , Aitor Morales, José J. Vague, Vicente Boria, Isabel Montero
SPACE MICROWAVE WEEK  (Noordwijk, Holanda. 08/05/2023)

Resumen:

One of the main goals of the current microwave space components' designers is that they can withstand the increasingly higher RF power requirements that must be considered at the output stages of transmitters. In this work, we propose a periodically grooved metallic surface profile that can significantly reduce the occurrence of multipactor effect in microwave components under vacuum conditions. The proposed technique has been applied to the top and bottom surfaces of a rectangular waveguide, and the multipactor power threshold with and without periodically grooved surfaces has been compared.

The reason why the resonant multipactor effect between the top and bottom grooved waveguide walls is reduced, differs from classical solutions based on the use of material coatings with low secondary emission yield. In the proposed rectangular waveguide with periodically grooved surfaces, the significant reduction of the multipactor effect achieved is caused by the reduction of the electric field level near the periodic grooves. Consequently, the electron staid time and the temporal dispersion of the secondary electron generation are increased. In this way, the generated secondary electrons are deviated from the resonant phase associated with the double-surface resonant multipactor effect.

The simulated 3-D electric field distribution inside the proposed waveguide with metallic grooved surfaces, where a triangular profile is used, has been calculated for different groove depths, thus demonstrating that the otherwise uniform E-field distribution of the TE₁₀ fundamental mode of the rectangular waveguide with smooth walls, is drastically modified near the top and bottom grooved waveguide walls. Indeed, the electric field can be significantly decreased near both walls in the space region next to the grooves by more than an order of magnitude compared to that in the central region of the waveguide.

Different profiles of 2-D periodic grooved surfaces may lead to the proposed reduction of the electric field level. However, the type of profile that can be effectively and precisely produced via mechanical manufacturing techniques is limited. Thus, we propose a periodical grooved surface along the direction of propagation with a triangular profile to be applied at the top and bottom walls of a rectangular waveguide.

Finally, in order to demonstrate the significant reduction in the expected multipactor effect, the power threshold in a rectangular waveguide with different depths of the grooved surfaces, as well as a benchmark prototype without the periodic grooves, has been calculated, showing a significant increase in terms of the power handling capability of the waveguide with the proposed technique. This approach can be applied to other more complex microwave devices.