E. Stamate* and K. Ohe

Nagoya Institute of Technology, Department of Systems Engineering
Showa-ku, Nagoya 466, Japan

A new method, based on electrical probes, allowing us to obtain the densities, nni and ne and temperatures, Tni and Te for both negative ions and electrons, respectively, was recently introduced [1]. Measurements were performed in an Ar/SF6 multipolar magnetic confined device. A magnetic filter was installed in a section perpendicular to the device axis, dividing the plasma into two regions, the so-called source and target plasmas. Measurements in the target plasma showed a discrepancy between the negative and positive charge densities, nni and ni about one order of magnitude, where ni was determined from the orbital motion limited model. Some typical density profiles for various SF6 flows are presented as a function of the discharge current Id in Fig.1, where the pressure was kept to be 5x10-4 Torr and the discharge voltage 50 V. In order to evaluate the discrepancy with more good accuracy, ne+nni and ni were detected by an electrostatic analyzer as well. The experimental results and their related discussions will be presented at the conference.

[1] E. Stamate and K. Ohe, IEEE Int. Conf. on Plasma Science, San Diego, IEEE Conf. Record- Abstracts, p. 303 (1997)