Controlling Secondary Electron Yield in High-Energy Systems
In high-energy environments, from particle accelerators to spacecraft surfaces, secondary electron behavior can make or break system performance. Engineers must accurately calculate secondary election yield (SEY) to control surface charging, reduce signal noise, and maintain operational stability.
Electro Magnetic Applications, Inc. (EMA) applies advanced measurement techniques and simulation capabilities to calculate this critical parameter.
“There’s definitely not a lot of people in the world that can do this type of measurement,” said EMA Staff Scientist Justin Christensen.
How SEY Influences Material Charging
SEY measures the ratio of secondary electrons emitted from a material’s surface to the number of primary electrons striking it. Engineers use this value to predict whether a surface will accumulate a positive or negative charge. Several factors influence SEY, including the material itself, as well as the energy and angle of the incident electrons.
“It’s kind of a counterintuitive thing,” Christensen explains. “You’d think if you’re throwing electrons out at material, it’s going to charge negatively. But there’s certain situations where you can knock more electrons out of the material than you’re depositing. So, you can get positive charging and negative charging depending on what the material is and what the incident energy is.”
Accurately determining SEY plays a critical role in technologies such as vacuum electronics, particle accelerators, and space systems, where uncontrolled charging can degrade performance or compromise system reliability.
Measuring SEY with Precision and Stability
EMA has developed a specialized experimental chamber designed to calculate SEY with high accuracy. The system incorporates a pulsed electron source operating from 20eV to 10keV, a hemispherical grid retarding field analyzer (HGRFA), and custom picometers that enable fast, highly sensitive current measurements.
“We have a really well controlled vacuum pressure gun so we can send in well-defined energy packets of electrons,” Christensen said.
To prevent spurious charging effects during measurement, the system minimizes injected charge and actively neutralizes both the positive and negative surface charging. A low-energy electron gun floods the analyzer volume to neutralize positive charge build up on the sample. In addition, a UV LED light source removes accumulated negative charge, allowing the system to maintain charge balance and ensure repeatable, reliable SEY measurements.
PIC-Based SEY Modeling
Ansys Charge Plus enables simulation of SEY via its particle-in-cell (PIC) solver. Charge Plus combines electromagnetic, fluid, and particle physics solvers for powerful multiphysics simulations. By incorporating experimental SEY data from the measurement chamber, Charge Plus allows engineers to model complex phenomena such as multipaction effects and charging behavior commonly encountered in space environments.
Start SEY Characterization Today
Accurately understanding and measuring SEY is essential for the analysis of vacuum electronics, particle accelerators, and space systems. EMA combines precision measurements with advanced Charge Plus simulation to deliver comprehensive SEY characterization enabling engineers to mitigate charging risks and optimize material performance in demanding environments.
Build a strong foundation for reliable system performance today. Contact EMA here to get started.
