Probing changes in secondary electron yield from copper electrodes due to surface defects and changes in crystal orientation

Abstract

There is considerable interest in mitigating secondary electron emission (SEE) from surfaces and electrodes produced by incident electrons, due to the deleterious effects of SEE in vacuum electron devices, accelerators, and other technologies. Since surface conditions are known to affect SEE, here the role played by crystal orientation and a vacancy (which is a simple example of a surface defect) is probed through Monte Carlo simulations. The effect of the lattice imperfection on the frequency-dependent permittivity, which then influences inelastic energy losses, mean free paths, and secondary generation profiles, is obtained on the basis of density-functional theory. The Monte Carlo simulations are in good agreement with previous experimental reports. The results indicate that the secondary electron yield for pure copper is the highest for the 110 orientation and the lowest for the 111 case, with a relatively higher differential predicted between a single vacancy and ideal copper for the 111 orientation. The results underscore the benefit of annealing or reducing inhomogeneities through laser or charged particle beam surface treatments.

Suppression of Secondary Electron Emission from Nickel Surface by Graphene Composites Based on First-Principles Method

“…Although we provided an insight into the mechanism, more abundant practical cases of surface modification are required to refine and strengthen the theory. In addition, the results of DFT calculations can also provide a basis for the first principles correction of MC simulations of SEY on the surface after surface modification [ 50 , 51 , 52 ]. This proposed mechanism supported by DFT calculations is of practical significance for a simplified expression of the correction methods in future MC simulations.…”

A continuum approach for multipactor using Vlasov–Poisson analysis

“…Electrons from the incident swarm may either be absorbed, undergo inelastic interactions within the material with a finite probability of re-emergence at lower energy, or undergo an elastic reflection. In the model, each outcome is weighted by the corresponding probabilities that are energy dependent [9,33]. These collective probabilities then generate an overall SEY.…”

“…The multipactor phenomenon is governed by the sustained generation of secondary electrons from one or more surfaces upon synchronization of the primary electron swarm dynamics with externally applied radiofrequency (RF) fields [1][2][3][4][5][6][7][8][9][10]. In the multipactor phenomenon, continuous charge growth occurs when the average secondary electron yield (SEY) exceeds unity.…”

“…Simulation studies of the swarm dynamics were performed with one spatial coordinate and one velocity variable to probe multipactor between two parallel plates. The spatially one-dimensional (1D) analysis ignores the possibilities of incident electrons striking the electrode surface at different angles, which would alter penetration depths, the emitted flux, and affect the energy distributions of secondary electrons, as has been probed by our group elsewhere [9]. To reasonably neglect any velocity components tangential to the parallel plates, a spatially uniform oscillatory electric-field oriented normally to the parallel plates is simulated.…”