Physics – Plasma Physics
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p41c1635d&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P41C-1635
Physics
Plasma Physics
[6250] Planetary Sciences: Solar System Objects / Moon, [7831] Space Plasma Physics / Laboratory Studies And Experimental Techniques, [7849] Space Plasma Physics / Plasma Interactions With Dust And Aerosols, [7855] Space Plasma Physics / Spacecraft Sheaths, Wakes, Charging
Scientific paper
Surfaces of airless natural bodies, such as the Moon and asteroids, and spacecraft in space are exposed to solar ultraviolet radiation that creates a photoelectron sheath that dominates the near-surface plasma environment. In order to reproduce and investigate this photoelectron layer, we conduct experiments in vacuum with Xe excimer lamps that emit UV light at ~172 nm (7.21 eV) which is of sufficient intensity to create a photoelectron layer with a characteristic length on the order of several centimeters. We utilize surfaces, such as Zr and CeO2 that have a low work function and a high photoelectron emission yield to maximize the electron density. In order to repel stray electrons that are produced by other surfaces in the chamber, and to define a reference potential, a negatively biased grid is placed 7.5 cm above the surface. The surface and the grid are used as a retarding potential analyzer to determine the energy distribution of the electrons emitted from the surface. When the grid is biased to -20 V, the emitted electrons have an approximately Maxwellian energy distribution with a characteristic temperature of 1.4 ± 0.3 eV. A Langmuir probe is also used as a diagnostic tool to find the effective electron temperature and electron density within the pure electron plasma, and is moved in order to probe different heights above the surface. The derived densities and potentials are compared with those predicted by 1-D PIC code simulations.
Dove Adrienne
Horanyi Mihaly
Poppe Andreas
Robertson S. H.
Wang Xinhua
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