White Paper: Aerospace
Taming Electron Avalanches: Multipaction-Resistant Cable Design For High-Power Signals In Space
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Understanding and mitigating multipaction is critical for ensuring reliability and performance in high-power RF and microwave systems. In this white paper, we explore the physics behind multipaction, its impact on coaxial cable assemblies, and the key design strategies, advanced materials, and simulation tools used to prevent failure in demanding aerospace, defense, satellite, and deep-space communication applications.
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Overview
This document, titled "Taming Electron Avalanches: Multipaction-Resistant Cable Design for High-Power Signals in Space" by Maddiel Gonzalez, MegaPhase VP & CTO, addresses the critical challenge of multipaction in space-based high-power RF and microwave communication systems. Multipaction is a resonant electron discharge phenomenon that occurs in the high-vacuum environment of space, where free electrons, accelerated by high-frequency RF electric fields, induce secondary electron emissions. This leads to self-sustaining electron avalanches that can severely degrade signal transmission, cause signal loss, distortion, increased noise, and potentially damage hardware through thermal runaway and arcing.
The paper explains that multipaction arises only when three conditions coincide: (1) Mean Free Path (MFP) dominance, where electrons can travel long distances unimpeded due to the vacuum, (2) RF electric field resonance, where electron transit times align with the RF field’s oscillation, enabling resonant acceleration, and (3) Secondary Electron Yield (SEY) greater than one, meaning each electron impact produces more than one secondary electron. Multipaction mostly initiates at cable-to-connector or connector-to-connector interfaces, where gaps and irregular geometries enable resonant electron trajectories.
To mitigate multipaction, the document discusses key design features and materials. Connector geometries with rounded edges, slanted or wedge-shaped surfaces, and venting to release volatiles reduce electron accumulation and prevent resonance conditions. Material selection is critical: thermally conductive dielectrics like Fluoroloy® help dissipate heat caused by electron impacts, while space-grade connector materials such as beryllium copper resist fatigue, corrosion, and thermal extremes better than alternatives. Surface coatings with low secondary electron yields (SEY), including novel laser-ablated nanostructures, suppress electron emission.
The paper highlights the necessity of a system-level design approach integrating power levels, frequencies, thermal environments, and impedance matching to assess multipaction risk, especially as systems evolve towards higher power, frequency, and miniaturization. Advanced 3D electromagnetic simulations, like CST Studio Suite with Spark3D, enable predictive modeling of electron trajectories and resonant modes before hardware fabrication.
Ultimately, MegaPhase embodies these principles by producing specialized high-performance coaxial cables and connectors designed for multipaction resistance and long-term phase stability in harsh space conditions. Manufactured and thoroughly tested in-house, MegaPhase products help ensure mission-critical communication systems maintain signal integrity and reliability over deep-space missions where repair is impossible.
In summary, the document stresses that intelligent geometry, material choice, surface engineering, simulation-driven design, and rigorous manufacturing are essential to tame electron avalanches and achieve dependable high-power RF signal transmission in space.