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Title: Field Electron Emission from Gold Dust Grains

Abstract

There is a number of areas in space where hot electrons represent a substantial constituent of the plasma environment. In such a case, any immersed dust grain could reach a very high negative surface potential. This potential is then limited by the field electron emission.In present contribution, we continue our previous investigation using 3D-electrodynamic quadrupole for dust grain trapping. We are able to charge a single trapped grain up to several hundreds of volts of negative surface potential using an electron gun. This potential is sufficient for observations of the field emission from micron size grains. Because there is lack of data on field electron emission from dielectric materials, we use gold spheres. Observed work function was in accordance with tabulated value. Nevertheless, the coarseness of the grains surfaces should be taken into account.

Authors:
; ; ;  [1]
  1. Charles University, Faculty of Mathematics and Physics, V Holesovickach 2, Prague (Czech Republic)
Publication Date:
OSTI Identifier:
20726728
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 799; Journal Issue: 1; Conference: 4. international conference on the physics of dusty plasmas, Orleans (France), 13-17 Jun 2005; Other Information: DOI: 10.1063/1.2134582; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; COSMIC DUST; DIELECTRIC MATERIALS; ELECTRODYNAMICS; ELECTRON EMISSION; ELECTRON GUNS; ELECTRONS; FIELD EMISSION; GOLD; PLASMA; QUADRUPOLES; SURFACE POTENTIAL; SURFACES; TRAPPING; WORK FUNCTIONS

Citation Formats

Pavlu, J., Richterova, I., Safrankova, J., and Nemecek, Z.. Field Electron Emission from Gold Dust Grains. United States: N. p., 2005. Web. doi:10.1063/1.2134582.
Pavlu, J., Richterova, I., Safrankova, J., & Nemecek, Z.. Field Electron Emission from Gold Dust Grains. United States. doi:10.1063/1.2134582.
Pavlu, J., Richterova, I., Safrankova, J., and Nemecek, Z.. Mon . "Field Electron Emission from Gold Dust Grains". United States. doi:10.1063/1.2134582.
@article{osti_20726728,
title = {Field Electron Emission from Gold Dust Grains},
author = {Pavlu, J. and Richterova, I. and Safrankova, J. and Nemecek, Z.},
abstractNote = {There is a number of areas in space where hot electrons represent a substantial constituent of the plasma environment. In such a case, any immersed dust grain could reach a very high negative surface potential. This potential is then limited by the field electron emission.In present contribution, we continue our previous investigation using 3D-electrodynamic quadrupole for dust grain trapping. We are able to charge a single trapped grain up to several hundreds of volts of negative surface potential using an electron gun. This potential is sufficient for observations of the field emission from micron size grains. Because there is lack of data on field electron emission from dielectric materials, we use gold spheres. Observed work function was in accordance with tabulated value. Nevertheless, the coarseness of the grains surfaces should be taken into account.},
doi = {10.1063/1.2134582},
journal = {AIP Conference Proceedings},
number = 1,
volume = 799,
place = {United States},
year = {Mon Oct 31 00:00:00 EST 2005},
month = {Mon Oct 31 00:00:00 EST 2005}
}
  • Dust grains in a space and accordingly in our laboratory simulation are charged by various processes. An impact of energetic ions leads to deposition of the positive charge on the grain. This effect increases the grain potential and the electric field at grain surface up to a threshold. When the threshold is reached, accumulated charge becomes spontaneously released. This discharging current was usually attributed to field ionization of a gas surrounding the grain or ion field evaporation of the grain material and thus it would be a function of the surface potential only. However, our previous study indicated that themore » main process discharging dust grains charged by the ion beam is the field desorption of beam ions deposited on the grain surface.The paper continues mentioned studies. We have used spherical Au grains and exposed them to a beam of He ions that charged the grain to high positive potentials. We have found that the discharging current is determined not only by the surface field intensity but it strongly depends on the structure of the grain surface.« less
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  • We present a combined experimental and simulation study of the charging of the spherical gold samples by an electron beam in a 0.15-10 keV range of beam energies. Experiments on grains with diameters of the order of 10{sup -6} m show that the charge (or surface potential) of grains levitating in a guadrupole trap is a function of both grain diameter and beam energy. Monte Carlo simulations reveal that an increase of the grain potential with the beam energy for a fixed diameter or a surface potential decrease with the grain diameter for a given beam energy are connected withmore » changes of the relative number of backscattered primary electrons. The results of simulations are in a good quantitative agreement with previously published as well as our fresh experimental data.« less
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  • Electrons impinging on a target can release secondary electrons and/or they can be scattered out of the target. It is well established that the number of escaping electrons per primary electron depends on the target composition and dimensions, the energy, and incidence angle of the primary electrons, but there are suggestions that the target's shape and surface roughness also influence the secondary emission. We present a further modification of the model of secondary electron emission from dust grains which is applied to non-spherical grains and grains with defined surface roughness. It is shown that the non-spherical grains give rise tomore » a larger secondary electron yield, whereas the surface roughness leads to a decrease in the yield. Moreover, these effects can be distinguished: the shape effect is prominent for high primary energies, whereas the surface roughness predominantly affects the yield at the low-energy range. The calculations use the Lunar Highlands Type NU-LHT-2M simulant as a grain material and the results are compared with previously published laboratory and in situ measurements.« less