Formation and extraction of a dense plasma jet from a helicon-plasma-injected inertial electrostatic confinement device

Ulmen, Benjamin

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https://hdl.handle.net/2142/46687 Copy

Description

Title

Formation and extraction of a dense plasma jet from a helicon-plasma-injected inertial electrostatic confinement device

Author(s)

Ulmen, Benjamin

Issue Date

2014-01-16T17:59:05Z

Director of Research (if dissertation) or Advisor (if thesis)

Miley, George H.

Doctoral Committee Chair(s)

Miley, George H.

Committee Member(s)

• Eden, James G.
• Ruzic, David N.
• Stubbins, James F.
• Marsh, Charles P.

Department of Study

Nuclear, Plasma, & Rad Engr

Discipline

Nuclear Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Inertial Electrostatic Confinement (IEC)
• Plasma
• Jet-Model
• Gridded Energy Analyzer
• Piezoelectric Force Sensor
• Faraday Cup
• COMSOL Modeling

Abstract

An inertial electrostatic confinement (IEC) device has several pressure and grid-geometry dependent modes of operation for the confinement of plasma. Although the symmetric grid star-mode is the most often studied for its application to fusion, the asymmetric grid jet-mode has its own potential application for electric space propulsion. The jet-mode gets its name from the characteristic bright plasma jet emanating from the central grid. In this dissertation work, a full study was undertaken to provide an understanding on the formation and propagation of the IEC plasma jet-mode. The IEC device vacuum system and all diagnostics were custom assembled during this work. Four diagnostics were used to measure different aspects of the jet. A spherical plasma probe was used to explore the coupling of an external helicon plasma source to the IEC device. The plasma current in the jet was measured by a combination of a Faraday cup and a gridded energy analyzer (GEA). The Faraday cup also included a temperature sensor for collection of thermal power measurements used to compute the efficiency of the IEC device in coupling power into the jet. The GEA allowed for measurement of the electron energy spectra. The force provided by the plasma jet was measured using a piezoelectric force sensor. Each of these measurements provided an important window into the nature of the plasma jet. COMSOL simulations provided additional evidence needed to create a model to explain the formation of the jet. It will be shown that the jet consists of a high energy electron beam having a peak energy of approximately half of the full grid potential. It is born near the aperture of the grid as a result of the escaping core electrons. Several other attributes of the plasma jet will be presented as well as a way forward to utilizing this device and operational mode for future plasma space propulsion.

Graduation Semester

2013-12

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http://hdl.handle.net/2142/46687

Copyright and License Information

Copyright 2013 Benjamin A Ulmen

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