Influence of the electron cross-field diffusion in negative ion sources with the transverse magnetic field and the plasma-electrode bias.
The physical mechanisms involved in the extraction of H(-) ions from the negative ion source are studied with a PIC 2D3V code. The effect of a weak magnetic field transverse to the extraction direction is taken into account, along with a variable bias voltage applied on the plasma electrode (PE). In addition to previous modeling works, the electron diffusion across the magnetic field is taken into account as a simple one-dimensional random-walk process. The results show that without PE bias, the value of the diffusion coefficient has a significant influence upon the value of the extracted H(-) current. However, the value of this coefficient does not affect qualitatively the mechanism leading to the peak of extracted H(-) ion current observed for an optimum value of the PE bias.
Kuppel
S
S
Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
Matsushita
D
D
Hatayama
A
A
Bacal
M
M