Motivation and Concept for Improved Laboratory Simulation of Space Electron Fluxes

Many space environments contain energetic electrons distributed across a broad spectrum of energies which are damaging to spacecraft materials and components. To characterize degradation and ensure adequate end-of-life performance, studies are often conducted in which samples are exposed to energetic electron fluxes in vacuum chambers. However, conventional electron guns used for such testing emit electrons monoenergetically, whereas the actual space environment contains electrons across a spectrum of energies. Physical phenomena resulting from energetic electron irradiation depend strongly on the energy of the incident particles, and synergistic effects can result from the combined effects of multiple energies. Therefore, it is questionable how well many vacuum chamber experiments represent the on-orbit degradation behavior, and a clear need exists for improved laboratory simulation of space electron fluxes. This paper provides a brief review of previous studies, underscores the limitations of monoenergetic fluxes, and discusses several alternatives for simulating the space electron environment in a laboratory. Next, a concept for a novel multi-energy electron source is presented. This source presents numerous advantages over the existing techniques for laboratory simulation of space electron fluxes. Finally, Monte Carlo N-Particle (MCNP) simulations are presented for energetic electrons incident on polyimide. These simulations demonstrate the proposed multi-energy electron gun is capable of producing space-representative damage with higher accuracy than monoenergetic guns.