نتایج جستجو برای: charging dust grains
تعداد نتایج: 79843 فیلتر نتایج به سال:
Introduction: Much of what we know about airless bodies in the solar system comes from observation of their surface or surface processes. From observations come hypotheses or models that, in favorable cases, can be constrained by additional observations on returned samples. Here, we show that other useful constraints arise from the extant knowledge of surface science processes occurring in othe...
The structure of a discharge across a magnetic field in a dusty plasma is analysed. The dust macroparticles are negatively charged, but are unmagnetized because of their high mass. The electrons are highly magnetized, and the ions have intermediate magnetization. This results in different transport rates of the different species across the magnetic field. Depending on the size of the magnetic f...
[1] The lunar surface represents a complex plasma environment due to the presence of solar ultraviolet (UV) radiation, the incoming solar wind flux and charged, levitated micron‐ and sub‐micron sized dust particles. Photoemission due to solar UV radiation dominates the charging environment, creating a photoelectron sheath above the lunar surface. To further investigate the dusty plasma environm...
[1] Dust grains have been observed to levitate above the surface of the Moon and as spokes in Saturn’s rings. In order to gain a better understanding of these observations, we have performed levitation experiments on dust grains in a low-density plasma. Plasma sheath potential profiles, measured by an emissive probe, are used to determine the spatial dependence of the electric force on a grain ...
[1] Dusty regolith particles accumulate charge through grain-grain contact and contact with various surfaces. These processes affect vertical and horizontal transport and may cause electrical discharges in dust storms. We report the results of a simple experimental setup used to investigate the contact charging properties of two planetary analog dust samples: lunar (JSC-1) and Martian (JSC-Mars...
The effect of negative ions on the charging of dust particles in a plasma is investigated experimentally. A plasma containing a very low percentage of electrons is formed in a single-ended Q machine when SF6 is admitted into the vacuum system. The relatively cold Q machine electrons Te 0.2 eV readily attach to SF6 molecules to form SF6 − negative ions. Calculations of the dust charge indicate t...
Introduction: The surface of the Moon, like any object in a plasma, charges to an electrostatic potential that minimizes the total incident current [1]. The charging currents come from four main sources: photoemission of electrons (Jph), plasma electrons (Je), plasma ions (Ji), and secondary electrons (Jsec). (Jsec arises primarily from surface ionization by plasma electrons.) The lunar dayside...
Understanding of various charging processes of dust grains is important in many different industrial applications as well as in the space research and theoretical studies of charging. An impact of energetic ions onto a dust grain leads to transfer of charge to the grain. This effect increases the charge of the dust grain until an equilibrium value is reached. After charging, the ion beam is swi...
A dusty plasma is an ionized gas containing dust particles, with sizes ranging from tens of nanometers to hundreds of microns. The interaction of the dust particles with the plasma and ambient environment results in a charging of the dust grains. This Chapter summarizes our basic knowledge of dusty plasmas with applications in space, industry and the laboratory. The Introduction (Section 1) pro...
An experiment is described in which monodisperse dust grains are levitated within a dc sheath above a conducting plate in argon plasma. For plate bias voltages that are not too negative ~>210 electron temperatures!, the observed dust levitation heights are near to values calculated from a model combining equations for the sheath with those for grain charging. When the plate is more negatively b...
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