An Experimental and Theoretical Investigation of Electron Beams Generated by a Dense Plasma Focus
Stygar, William Arthur
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https://hdl.handle.net/2142/70882
Description
Title
An Experimental and Theoretical Investigation of Electron Beams Generated by a Dense Plasma Focus
Author(s)
Stygar, William Arthur
Issue Date
1982
Department of Study
Nuclear Engineering
Discipline
Nuclear Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Nuclear
Abstract
The first direct measurements of the current and energy spectrum of an electron beam generated by a dense plasma focus are reported. The electron beam current is found to scale as
where I(,MB) is the main bank current at pinch time, for a Mather-type DPF with an initial deuterium fill gas pressure of 3 torr. The time integrated electron beam energy spectrum is found to follow roughly a power law,
(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI)
where E is the energy of the beam electrons and the exponent X scales as
A significant fraction of the measured spectra were found to have a bump on the high energy tail and hence did not follow a simple power law. For a pinch current of (TURN)450 kiloamps the peak beam current is found to be 16 kA and the exponent of the energy spectrum power law is - 3.3 (+OR-) 0.5. The first simultaneous measurement of the DPF ion and electron beam energy spectra is also reported and indicates that the two have the same power law dependence, within experimental error.
The main bank current was measured with a Rogowski coil, the beam current was measured with a Faraday cup, and a magnetic spectrometer was used to determine the time integrated beam energy spectrum. New calculations are presented that give the exact high frequency response of a Rogowski coil for arbitrary terminating impedance, which are useful for interpreting Rogowski coil signals. Calculations that have led to improvements in the design of a commonly used high current electron beam Faraday cup are also reported, along with the improved design that was used for the measurements. The bandwidth of the improved Faraday cup was measured with a Hewlett-Packard network analyzer and was found to be 450 MHz (-3 dB point).
A one-dimensional code (DPFR) was written to model the collapse phase and beam production of the dense plasma focus. DPFR solves the two fluid-Maxwell-circuit equations for a high density, z-pinch type plasma in radial geometry, and includes both classical and anomalous transport coefficients. A simple electron runaway model is incorporated into the code to calculate the electron beam current. The scaling of the electron beam current predicted by DPFR is in qualitative agreement with the experimental results.
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