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Physics of the intermediate layer between a plasma and a collisionless sheath and mathematical meaning of the Bohm criterion

2012Journal article Open access
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dc.contributor.authorAlmeida, N. A.
dc.contributor.authorBenilov, M. S.
dc.date.accessioned2019-11-11T15:02:30Z
dc.date.available2019-11-11T15:02:30Z
dc.date.issued2012
dc.description.abstractA transformation of the ion momentum equation simplifies a mathematical description of the transition layer between a quasi-neutral plasma and a collisionless sheath and clearly reveals the physics involved. Balance of forces acting on the ion fluid is delicate in the vicinity of the sonic point and weak effects come into play. For this reason, the passage of the ion fluid through the sonic point, which occurs in the transition layer, is governed not only by inertia and electrostatic force but also by space charge and ion-atom collisions and/or ionization. Occurrence of different scenarios of asymptotic matching in the plasma-sheath transition is analyzed by means of simple mathematical examples, asymptotic estimates, and numerical calculations. In the case of a collisionless sheath, the ion speed distribution plotted on the logarithmic scale reveals a plateau in the intermediate region between the sheath and the presheath. The value corresponding to this plateau has the meaning of speed with which ions leave the presheath and enter the sheath; the Bohm speed. The plateau is pronounced reasonably well provided that the ratio of the Debye length to the ion mean free path is of the order of 10 3 or smaller. There is no such plateau if the sheath is collisional and hence no sense in talking of a speed with which ions enter the sheath.pt_PT
dc.description.versioninfo:eu-repo/semantics/publishedVersionpt_PT
dc.identifier.citationAlmeida, N. A., & Benilov, M. S. (2012). Physics of the intermediate layer between a plasma and a collisionless sheath and mathematical meaning of the Bohm criterion. Physics of Plasmas, 19(7), 073514.pt_PT
dc.identifier.doi10.1063/1.4737080pt_PT
dc.identifier.urihttp://hdl.handle.net/10400.13/2596
dc.language.isoengpt_PT
dc.publisherAIP Publishingpt_PT
dc.relationCathode spots in high-pressure DC gas discharges: self-organization phenomena
dc.relationStrategic Project - UI 219 - 2011-2012
dc.subjectIntermediate layer between a plasma and a collisionless sheathpt_PT
dc.subjectBohm criterionpt_PT
dc.subject.pt_PT
dc.subjectFaculdade de Ciências Exatas e da Engenhariapt_PT
dc.titlePhysics of the intermediate layer between a plasma and a collisionless sheath and mathematical meaning of the Bohm criterionpt_PT
dc.typejournal article
dspace.entity.typePublication
oaire.awardTitleCathode spots in high-pressure DC gas discharges: self-organization phenomena
oaire.awardTitleStrategic Project - UI 219 - 2011-2012
oaire.awardURIinfo:eu-repo/grantAgreement/FCT/3599-PPCDT/PTDC%2FFIS%2F68609%2F2006/PT
oaire.awardURIinfo:eu-repo/grantAgreement/FCT/6817 - DCRRNI ID/PEst-OE%2FMAT%2FUI0219%2F2011/PT
oaire.citation.startPage073514pt_PT
oaire.citation.titlePhysics of Plasmaspt_PT
oaire.citation.volume19(7)pt_PT
oaire.fundingStream3599-PPCDT
oaire.fundingStream6817 - DCRRNI ID
person.familyNameAlmeida
person.familyNameBenilov
person.givenNameNelson
person.givenNameMikhail
person.identifier.ciencia-id0516-6FAA-27E2
person.identifier.ciencia-id0F14-A79A-97C1
person.identifier.orcid0000-0002-6499-3609
person.identifier.orcid0000-0001-9059-1948
person.identifier.ridM-6228-2013
person.identifier.ridK-4443-2015
person.identifier.scopus-author-id7003469070
person.identifier.scopus-author-id7005138676
project.funder.identifierhttp://doi.org/10.13039/501100001871
project.funder.identifierhttp://doi.org/10.13039/501100001871
project.funder.nameFundação para a Ciência e a Tecnologia
project.funder.nameFundação para a Ciência e a Tecnologia
rcaap.rightsopenAccesspt_PT
rcaap.typearticlept_PT
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