A langmuir multi-probe system for the characterization of atmospheric pressure arc plasmas

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dc.contributor.advisor Nicholls, J. R. en_UK
dc.contributor.author Fanara, C. en_UK
dc.date.accessioned 2005-11-23T14:36:16Z
dc.date.available 2005-11-23T14:36:16Z
dc.date.issued 2003-04 en_UK
dc.identifier.uri http://hdl.handle.net/1826/96
dc.description.abstract The 'high-pressure' atmospheric (TIG) arc plasma is studied by means of a multi-Langmuir probe system. In order to determine the appropriate regime of operation, definitions of the plasma parameters for the description of the argon arc are considered and evaluations are presented. A description of the probe basic techniques is followed by an in-depth discussion of the different regimes of probe operation. The emphasis is put on atmospheric and flowing (arc) regimes. Probe sheath theories are compared and “Nonidealities” like cooling due to plasma-probe motion and probe emission mechanisms are then described. The extensive literature review reveals that the existing probe theories are inappropriate for a use in the TIG arc, because of ‘high’ pressure (atmospheric), broad range of ionization across the arc, flowing conditions, and ultimately, to the uncertainty about onset of Local Thermodynamical Equilibrium. The Langmuir probe system is built to operate in floating and biased conditions. The present work represents the first extensive investigation of electrostatic probes in arcs where the experimental difficulties and the primary observed quantities are presented in great detail. Analysis methodologies are introduced and experimental results are presented towards a unified picture of the resulting arc structure by comparison with data from emission spectroscopy. Results from different measurements are presented and comparison is made with data on TIG arcs present in literature. Probe obtained temperatures are lower than the values obtained from emission spectroscopy and this ‘cooling’ is attributed to electron-ion recombination. However, it is believed that probes can access temperatures regions not attainable by emission spectroscopy. Only axial electric potential and electric field are obtained because of the equipotential-probe requirement. Estimations of the sheath voltage and extension are obtained and a qualitative picture of the ion and electron current densities within the arc is given. en_UK
dc.format.extent 1883 bytes
dc.format.extent 4772698 bytes
dc.format.mimetype text/plain
dc.format.mimetype application/pdf
dc.language.iso en_UK en_UK
dc.publisher Cranfield University en_UK
dc.subject.other atmospheric pressure plasma en_UK
dc.subject.other Langmuir probes en_UK
dc.subject.other probe sheath theory en_UK
dc.subject.other TIG arc en_UK
dc.subject.other electrostatic probes en_UK
dc.title A langmuir multi-probe system for the characterization of atmospheric pressure arc plasmas en_UK
dc.type Thesis or dissertation en_UK
dc.type.qualificationlevel Doctoral
dc.type.qualificationname PhD
dc.publisher.department School of Industrial and Manufacturing Science

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