A biased probe analysis of potential well formation in an electron only, low beta Polywell magnetic field

Carr, Matthew; Khachan, Joe

doi:10.1063/1.4804279

Title: A biased probe analysis of potential well formation in an electron only, low beta Polywell magnetic field

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Abstract

Orbital limited motion theory has been applied to two biased probes in a low beta Polywell. The cases studied include electron injection, magnetic field scaling, Polywell bias scaling, and radial position profiles. Langmuir's original orbital limited motion results for a monoenergetic electron beam are shown to be in excellent agreement for electron injection into the Polywell. A distribution function is proposed for the electron plasma characteristics in the centre of the magnetic null and confirmed with experimental results. A translational stage was used to measure the radial plasma potential profile. In other experiments, two probes were used to simultaneously measure the profiles in both the null and a position halfway along a corner cusp. The results confirm a radial potential well created by electron trapping in the device. In addition, we present preliminary results of the potential well scaling with the magnetic field, Polywell bias voltage, and the injected beam current. The electron population was found to maintain non-equilibrium in all cases studied.

Authors:

Carr, Matthew; Khachan, Joe ^[1]

Department of Plasma Physics, School of Physics A28, University of Sydney NSW 2006 (Australia)

Publication Date:: Wed May 15 00:00:00 EDT 2013

OSTI Identifier:: 22218613

Resource Type:: Journal Article

Journal Name:: Physics of Plasmas

Additional Journal Information:: Journal Volume: 20; Journal Issue: 5; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BEAM CURRENTS; BETA RATIO; CHARGED-PARTICLE TRANSPORT; DISTRIBUTION FUNCTIONS; ELECTRON BEAM INJECTION; ELECTRONS; MAGNETIC FIELDS; PLASMA; PLASMA CONFINEMENT; PLASMA POTENTIAL; PLASMA RADIAL PROFILES; PROBES; TRAPPING

Citation Formats


                    Carr, Matthew, and Khachan, Joe. A biased probe analysis of potential well formation in an electron only, low beta Polywell magnetic field.  United States: N. p., 2013. 
        Web.  doi:10.1063/1.4804279.

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                    Carr, Matthew, & Khachan, Joe. A biased probe analysis of potential well formation in an electron only, low beta Polywell magnetic field.  United States.  https://doi.org/10.1063/1.4804279

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                    Carr, Matthew, and Khachan, Joe. 2013.  
        "A biased probe analysis of potential well formation in an electron only, low beta Polywell magnetic field".  United States.  https://doi.org/10.1063/1.4804279.

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@article{osti_22218613,

  title        = {A biased probe analysis of potential well formation in an electron only, low beta Polywell magnetic field},

  author       = {Carr, Matthew and Khachan, Joe},

  abstractNote = {Orbital limited motion theory has been applied to two biased probes in a low beta Polywell. The cases studied include electron injection, magnetic field scaling, Polywell bias scaling, and radial position profiles. Langmuir's original orbital limited motion results for a monoenergetic electron beam are shown to be in excellent agreement for electron injection into the Polywell. A distribution function is proposed for the electron plasma characteristics in the centre of the magnetic null and confirmed with experimental results. A translational stage was used to measure the radial plasma potential profile. In other experiments, two probes were used to simultaneously measure the profiles in both the null and a position halfway along a corner cusp. The results confirm a radial potential well created by electron trapping in the device. In addition, we present preliminary results of the potential well scaling with the magnetic field, Polywell bias voltage, and the injected beam current. The electron population was found to maintain non-equilibrium in all cases studied.},

  doi          = {10.1063/1.4804279},

  url          = {https://www.osti.gov/biblio/22218613},
  journal      = {Physics of Plasmas},

  issn         = {1070-664X},

  number       = 5,

  volume       = 20,

  place        = {United States},

  year         = {Wed May 15 00:00:00 EDT 2013},

  month        = {Wed May 15 00:00:00 EDT 2013}

}

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