Experimental Investigation of m=1 Diocotron Mode Growth at Low Electron Densities
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.
- Research Organization:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC) (US)
- DOE Contract Number:
- AC02-76CH03073
- OSTI ID:
- 814751
- Report Number(s):
- PPPL-3859; TRN: US0304349
- Resource Relation:
- Other Information: PBD: 21 Aug 2003
- Country of Publication:
- United States
- Language:
- English
Similar Records
Effects of background gas pressure on pure electron plasma dynamics in the electron diffusion gauge experiment
Dynamics of the m=1 diocotron mode in the electron diffusion gauge experiment