Experimental Characterization of Plasma Detachment from Magnetic Nozzles

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dc.contributor.advisorCloutier, Paul A.en_US
dc.contributor.advisorChang-Diaz, Franklin R.en_US
dc.contributor.committeeMemberAlexander, Daviden_US
dc.contributor.committeeMemberTittel, Frank K.en_US
dc.creatorOlsen, Christopheren_US
dc.date.accessioned2013-09-16T16:04:45Zen_US
dc.date.accessioned2013-09-16T16:04:56Zen_US
dc.date.available2013-09-16T16:04:45Zen_US
dc.date.available2013-09-16T16:04:56Zen_US
dc.date.created2013-05en_US
dc.date.issued2013-09-16en_US
dc.date.submittedMay 2013en_US
dc.date.updated2013-09-16T16:04:56Zen_US
dc.description.abstractMagnetic nozzles, like Laval nozzles, are observed in several natural systems and have application in areas such as electric propulsion and plasma processing. Plasma flowing through these nozzles is inherently tied to the field lines and must separate for momentum redirection or particle transport to occur. Plasma detachment and associated mechanisms from a magnetic nozzle are investigated. Experimental results are presented from the plume of the VASIMR® VX-200 device flowing along an axisymmetric magnetic nozzle and operated at two ion energies to explore momentum dependent detachment. The argon plume expanded into a 150m3 vacuum chamber where the background pressure was low enough that charge-exchange mean-free-paths were longer than experiment scale lengths. This magnetic nozzle system is demonstrated to hydrodynamically scale up to astrophysical plasmas, particularly the solar chromosphere, implying general relevance to all systems. Plasma parameters were mapped over a large spatial range using measurements from multiple plasma diagnostics. The data show that the plume does not follow the magnetic field lines. A mapped integration of the ion flux shows the plume may be divided into three regions where 1) the plume briefly follows the magnetic flux, 2) diverges quadratically before 3) expanding with linear trajectories. Transitioning from region 1→2, the ion flux departs from the magnetic flux suggesting ion detachment. An instability forms in region 2 driving an oscillating electric field that causes ions to expand before enhancing electron cross-field transport through anomalous resistivity. Transitioning from region 2→3 the electric field dissipates, the trajectories linearize, and the plume effectively detaches. A delineation of sub-to-super Alfvénic flow aligns well with the inflection points of the linearization without a change in magnetic topology. The detachment process is best described as a two part process: First, ions detach by a breakdown of the magnetic moment when the quantity |v/fcLB| becomes of order unity. Second, the turbulent electric field enhances electron transport up to a factor of 4±1 above collisional diffusion; electron cross-field velocities approximate that of the ions and depart on more centralized field lines. Electrons are believed to detach by breakdown of magnetic moment further downstream in the weaker magnetic field.en_US
dc.format.mimetypeapplication/pdfen_US
dc.identifier.citationOlsen, Christopher. "Experimental Characterization of Plasma Detachment from Magnetic Nozzles." (2013) Diss., Rice University. <a href="https://hdl.handle.net/1911/72016">https://hdl.handle.net/1911/72016</a>.en_US
dc.identifier.slug123456789/ETD-2013-05-402en_US
dc.identifier.urihttps://hdl.handle.net/1911/72016en_US
dc.language.isoengen_US
dc.rightsCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.en_US
dc.subjectPlasma detachmenten_US
dc.subjectMagnetic nozzleen_US
dc.subjectElectric propulsionen_US
dc.subjectMagnetic moment breakdownen_US
dc.subjectLoss of adiabaticityen_US
dc.subjectPlasma turbulenceen_US
dc.subjectPlasma transporten_US
dc.subjectCross-field diffusionen_US
dc.subjectPlasma diagnosticsen_US
dc.subjectLaboratory astrophysics scalingen_US
dc.subjectHelicon plasmaen_US
dc.subjectIon cyclotron heatingen_US
dc.subjectExperimental plasma physicsen_US
dc.titleExperimental Characterization of Plasma Detachment from Magnetic Nozzlesen_US
dc.typeThesisen_US
dc.type.materialTexten_US
thesis.degree.departmentPhysics and Astronomyen_US
thesis.degree.disciplineNatural Sciencesen_US
thesis.degree.grantorRice Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophyen_US
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