Engineered surfaces to control secondary electron emission for multipactor suppression

Sattler, James M.; Coutu, Ronald A.; Lake, Robert A.; Laurvick, Tod V.

doi:10.1109/naecon.2016.7856818

Cited by 3 publications

(2 citation statements)

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“…Recently, a new wall concept based nano-architected surfaces has been proposed to mitigate surface erosion and SEE [22][23][24][25]. Demonstration designs based on high-Z refractory materials have been developed, including architectures based on metal nanowires and nanofoams [26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the energy imparted by the sheath to the ions within the discharge determines the impact energy and incident angle of ions upon the surface, thus affecting the amount of material sputtered and consequently the wall erosion rate [20,21]. Thus, understanding how SEE affects sheath stability is crucial to make predictions of channel wall lifetime.Recently, a new wall concept based nano-architected surfaces has been proposed to mitigate surface erosion and SEE [22][23][24][25]. Demonstration designs based on high-Z refractory materials have been developed, including architectures based on metal nanowires and nanofoams [26][27][28][29][30].…”

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confidence: 99%

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Calculation of secondary electron emission yields from low-energy electron deposition in tungsten surfaces

Chang

Alvarado

Marian

2018

Applied Surface Science

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We present calculations of secondary electron emission (SEE) yields in tungsten as a function of primary electron energies between 50 eV and 1 keV and incidence angles between 0 and 90 • . We conduct a review of the established Monte Carlo methods to simulate multiple electron scattering in solids and select the best suited to study SEE in high-Z metals. We generate secondary electron yield and emission energy functions of the incident energy and angle and fit them to bivariate fitting functions using symbolic regression. We compare the numerical results with experimental data, with good agreement found. Our calculations are the first step towards studying SEE in nanoarchitected surfaces for electric propulsion chamber walls. IntroductionSecondary electron emission (SEE) is the emission of free electrons from a solid surface, which occurs when these surfaces are irradiated with external (also known as primary) electrons. SEE is an important process in surface physics with applications in numerous fields, such as electric propulsion [1-5], particle accelerators [6], plasma-walls in fusion reactors [7][8][9][10][11], electron microscopy and spectroscopy [12,13], radio frequency devices [14-16], etc. In Hall thrusters for electric propulsion, a key component is the channel wall lining protecting the magnetic circuits from the discharge plasma. These channel walls are a significant factor in Hall thruster performance and lifetime through its interactions with the discharge plasma. These interactions are governed by the sheath formed along the walls, and so the properties of the sheath determine the amount of electron energy absorbed by the wall, which in turn affects the electron dynamics within the bulk discharge [1,[17][18][19]. Furthermore, the energy imparted by the sheath to the ions within the discharge determines the impact energy and incident angle of ions upon the surface, thus affecting the amount of material sputtered and consequently the wall erosion rate [20,21]. Thus, understanding how SEE affects sheath stability is crucial to make predictions of channel wall lifetime.Recently, a new wall concept based nano-architected surfaces has been proposed to mitigate surface erosion and SEE [22][23][24][25]. Demonstration designs based on high-Z refractory materials have been developed, including architectures based on metal nanowires and nanofoams [26][27][28][29][30]. The idea behind these designs is to take advantage of very-high surface-to-volume ratios to reduce SEE and ion erosion by internal trapping and redeposition. Preliminary designs are based on W, W/Mo, and W/Re structures, known to have intrinsically low sputtering yields secondary

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