Experimental Investigation of m=1 Diocotron Mode Growth at Low Electron Densities

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Previous experiments on the Electron Diffusion Gauge showed that the diocotron mode damping increases with higher neutral gas filling pressure. Yet the energy dissipated from a rotating plasma by collisions with neutrals is predicted to excite the mode. To resolve this, experiments have been conducted to examine the coupling between expansion and the m=1 diocotron mode. Results from recent experiments have shown interesting phenomena: (1) The degree and sensitivity of mode growth is observed to be strongly dependent on filament conditions. Mode growth rates of nearly 20 sec{sup -1} have been observed even with negligible resistive drive. Specifically, at low ... continued below

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Paul, Stephen F.; Morrison, Kyle & Davidson, Ronald C. August 21, 2003.

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Previous experiments on the Electron Diffusion Gauge showed that the diocotron mode damping increases with higher neutral gas filling pressure. Yet the energy dissipated from a rotating plasma by collisions with neutrals is predicted to excite the mode. To resolve this, experiments have been conducted to examine the coupling between expansion and the m=1 diocotron mode. Results from recent experiments have shown interesting phenomena: (1) The degree and sensitivity of mode growth is observed to be strongly dependent on filament conditions. Mode growth rates of nearly 20 sec{sup -1} have been observed even with negligible resistive drive. Specifically, at low filament bias voltages (and correspondingly low electron densities {approx}1-2 x 10{sup 7} electrons/cm), the mode growth is very sensitive to the heating voltage across the filament, even though changes in filament heating voltage barely affect the plasma expansion, the plasma density profile, the filament emission, or the resulting electron density. (2) At low neutral gas pressure (<10{sup -9} Torr), the diocotron mode growth rate increases with neutral pressure. However, the growth rate is several orders of magnitude larger than theoretical predictions.

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INIS; OSTI as DE00814751

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  • Other Information: PBD: 21 Aug 2003

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  • Report No.: PPPL-3859
  • Grant Number: AC02-76CH03073
  • DOI: 10.2172/814751 | External Link
  • Office of Scientific & Technical Information Report Number: 814751
  • Archival Resource Key: ark:/67531/metadc739891

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  • August 21, 2003

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  • Oct. 18, 2015, 6:40 p.m.

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  • April 15, 2016, 9:08 p.m.

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Paul, Stephen F.; Morrison, Kyle & Davidson, Ronald C. Experimental Investigation of m=1 Diocotron Mode Growth at Low Electron Densities, report, August 21, 2003; Princeton, New Jersey. (digital.library.unt.edu/ark:/67531/metadc739891/: accessed September 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.