Simple polynomial approximation to modified Bethe formula low-energy electron stopping powers data

Taborda, A.; Desbrée, Aurélie; Reis, M.A.

doi:10.1016/j.nimb.2015.05.005

Cited by 3 publications

(4 citation statements)

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“…To resolve this, much effort has been devoted to modifying the Bethe formula, from which systematization of tabulated electron stopping powers for various elements and attempts to simplify the calculations have emerged. [45][46][47][48][49] In general, the use of these formulas for elements or compounds with fitting parameters requires a detailed and accurate supply of experimental data on which to base its physics and against which to test its predictions. [50] Nevertheless, the CSDA strategy may still become obsolete when an electron occasionally loses a large fraction of its energy in a single collision as well as when secondary electron emission distribution spectra are required.…”

Section: Inelastic Scatteringmentioning

confidence: 99%

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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Section: Inelastic Scatteringmentioning

confidence: 99%

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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“…In the case of the CSDA step, the simplified algorithm of Taborda et al for calculating the stopping power of electrons [16] was used, after which, making use of various algorithms and databases existing in DT2 [8], the above described models were implemented as an extra set of subroutines of the code.…”

Section: Resultsmentioning

confidence: 99%

“…This said, and after careful analysis of the detailed calculations by Shinotsuka [15], we have tested on electron stopping power data an approach similar to what has been carried out for protons and alpha particles ionisation cross-sections [9]. The result of this approach is a simple polynomial approximation to electron stopping powers published recently [16], which allows the recovery of the Shinotsuka results [15] to better than 20% for electron energies above 100 eV.…”

Section: Primarymentioning

confidence: 99%

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Nuclear Instruments and Methods in Physics Research Section B:

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Simple polynomial approximation to modified Bethe formula low-energy electron stopping powers data

Cited by 3 publications

References 16 publications

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

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

Energetic electron processes fluorescence effects for structured nanoparticles X-ray analysis and nuclear medicine applications

The atomic nucleus, nuclear radiation, and the interaction of radiation with matter

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