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Study of dust removal by standing wave electric curtain for application to solar cells on Mars

Multi-phase electric curtains generate traveling-waves which can lift and convey charged particles. We consider here single phase electric curtains that create a standing wave but, nevertheless, in certain conditions can expel the powder deposited above it. We present results of experiments performed in atmospheric air as well as in carbon dioxide for electrodes coated with an insulating material and for two powders under various pressures down to that existing on Mars (p/spl cong/7 mbar). In air (p=1 bar), a part of the powders is put into motion when raising the applied voltage. Under high enough gas pressure, the process becomes efficient and leads eventually to the deposited powder being totally expelled from the stressed zone only when there are discharges (dielectric barrier discharge-DBD) in the gas just over the surface of the insulating layer. The powder removal becomes more and more difficult when p is lowered. Below a pressure threshold, there is no total removal of deposited powder. For gas pressure around 7 mbar, a good powder removal requires a distance between axes of adjacent electrodes lower than 1 mm. The dust removal capability also depends on the size of the particles. When putting Mars dust simulant using a brush having an agglomeration effect, the removal is often satisfactory. But when injecting the same powder into the vessel under reduced pressure, the resulting layer of fine particles remains unperturbed by the action of electric field and DBDs. These observations are discussed in the light of the basic forces acting on particles.