Ion-induced electron emission reduction via complex surface trapping

A Monte Carlo model is developed and validated to understand the ion-induced electron emission (IIEE) characteristics of complex surfaces and to show the importance of using precise geometric features to examine surface morphology effects on the yield. The decrease in IIEE from carbon velvet is accurately simulated with two distinct geometries (based on SEM images), one composed of slanted, sparsely distributed fibers and the other of tightly packed, vertical fibers. Simulation results for tungsten fuzz using a cagelike geometry predict a reduction in the yield of ∼50% compared to flat W, contradictory to previous estimates. Collisional heatmaps using the cage geometry show that the angular independence of IIEE is due to electron trapping by the horizontally oriented fibers. These insights into the emission behavior of these surfaces provide guidance for the design of new surfaces that can improve the performance of plasma devices.