The Importance of Accurate Computation of Secondary Electron Emission for Modeling Spacecraft Charging

Authors

S. Clerc
John R. Dennison, Utah State UniversityFollow
C. D. Thomson

Document Type

Presentation

Journal/Book Title/Conference

9th Spacecraft Charging Technology Conference

Publisher

Spacecraft Charging Technology

Publication Date

2005

Abstract

Secondary electron emission is a critical contributor to the current balance in spacecraft charging. Spacecraft charging codes use a parameterized expression for the secondary electron yield δ(Eo) as a function of incident electron energy Eo. Simple three-step physics models of the electron penetration, transport and emission from a solid are typically expressed in terms of the incident electron penetration depth at normal incidence or range R(E_o ), and the mean free path of the secondary electron, λ(E). We recall classical models for the range R(E_o): a power law expression of the form b₁E_oⁿ¹, and a more general empirical bi-exponential expression R(Eo) = b₁E_o n₁+b₂E_oⁿ². Expressions are developed that relate the theoretical fitting parameters (λ, b₁, b₂, n₁ and n₂) to experimental terms (the energy E_max at the maximum secondary electron yield δ_max, the first and second crossover energies E₁ and E₂, and the asymptotic limits for d(Eo→∞)). In most models, the yield is the result of an integral along the path length of incident electrons. Special care must be taken when computing this integral. An improved fourth-order numerical method is presented and compared to the standard secondorder method. A critical step in accurately characterizing a particular spacecraft material is the determination of the model parameters in terms of the measured electron yield data. The fitting procedures and range models are applied to several measured data sets to compare their effectiveness in modeling the function δ(Eo) over the full range of incident energies, and in particular for determining crossover energies and critical temperatures.

Comments

Paper presented at the 9th Spacecraft Charging Technology Conference. PDF available for download through link above.

Recommended Citation

Clerc, S.; Dennison, John R.; and Thomson, C. D., "The Importance of Accurate Computation of Secondary Electron Emission for Modeling Spacecraft Charging" (2005). All Physics Faculty Publications. Paper 1479.
https://digitalcommons.usu.edu/physics_facpub/1479