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Descripción
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| The design and performances and of a simple circuit for fast sweep measurements using either, collecting and emissive Langmuir probes are discussed [1]. The experimental results obtained under ideal conditions with Maxwellian plasmas in electric discharges are presented and compared with those obtained with similar devices [2-4]. The experiments indicate that the effective upper bound for the maximum frequency sweep, using collecting probes in weakly ionized plasmas, is not caused by the limitations of the electrical circuitry. On the contrary, the pulse repetition time limit is originated by the speed acquired by the ions in a collisional mean free path. This fast sweep systems bias the probe by means of a time dependent voltage ramp and the massive ions are accelerated towards the probe for negative bias voltages would not follow the fast change of the probe electric field. In consequence, the drained probe current below the plasma potential, which is composed of attracted ions and repelled electrons, becomes affected by the slow response of ions to fast voltage ramps. The formation of the plasma sheath around the probe and consequently, the orbital motion of attracted ions is hindered by the fast change in the electric field around the probe. This inertial effect of heavy particles would be enhanced by the collisions of ions with neutrals which results in the local confinement of the massive particles. This collisional time-dependent response of collecting Langmuir probes is evidenced in the current voltage curves which are compared for different characteristic sweep times. The effect introduced by the neutral gas pressure in this collisional time-dependent response will be also discussed. | |
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Internacional
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Si |
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Nombre congreso
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VIII IWEP 2009 Innsbruck. 8th International Workshop on Electric Probes in Magnetized Plasmas Institute for Ion Physics and Applied Physics. |
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Tipo de participación
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960 |
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Lugar del congreso
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Innsbruck, Austria |
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Revisores
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Si |
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ISBN o ISSN
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978-3-902652-13-3 |
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DOI
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Fecha inicio congreso
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21/09/2009 |
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Fecha fin congreso
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24/09/2009 |
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0 |
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Hasta la página
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0 |
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Título de las actas
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Book of Abstract of the 8th International Workshop on Electric Probes in Magnetized Plasma and of the International Workshop "50 Years Plasma Physics in Innsbruck" |