| AVS 57th International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS-ThP |
| Session: | Plasma Science and Technology Poster Session |
| Presenter: | J.P. Sheehan, University of Wisconsin-Madison |
| Authors: | J.P. Sheehan, University of Wisconsin-Madison N. Hershkowitz, University of Wisconsin-Madison |
| Correspondent: | Click to Email |
In a multi-dipole chamber with dirty walls, the plasma potential is observed to be negative with respect to grounded wall in the tens of volts. The plasma is generated by hot filaments releasing monoenergetic primary electrons ranging from 35 to 60eV. The primaries can exist in significant concentrations relative to the plasma electrons (up to 0.5% primaries as measured by a planar Langmuir probe) and contribute to charge neutrality, but not significantly to current balance. It is observed that the plasma potential becomes more negative with increasing relative concentrations of primary electrons. The potential profile next to the wall was measured using an emissive probe in the limit of zero emission[1]. The negative potential in the bulk plasma drops an additional few Te radially to the wall. The radial and axial potential profiles resemble those found in a chamber with clean walls and a positive plasma potential except the entire profile is shifted 10 – 20V lower. Possible mechanisms for these observations are suggested.
References
[1] J. R. Smith, N. Hershkowitz, and P. Coakley, Rev. Sci. Instrum. 50, 210 1979.