AVS 52nd International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuP

Paper PS-TuP24
Characterization of an Energetic Neutral Beam Source

Tuesday, November 1, 2005, 4:00 pm, Room Exhibit Hall C&D

Session: Plasma Science and Technology Poster Session
Presenter: C. Helmbrecht, University of Houston
Authors: C. Helmbrecht, University of Houston
Q. Wang, University of Houston
V.M. Donnelly, University of Houston
D.J. Economou, University of Houston
G.F. Franz, University of Applied Sciences, Germany
Correspondent: Click to Email
The residual ion beam and the energetic neutral beam of a neutral beam source were characterized using an ion energy analyzer in combination with a calorimeter. The beam was extracted through a neutralizer metal grid with high aspect ratio holes separating a 13.56 MHz inductively coupled argon plasma from the differentially-pumped beam characterization chamber. By biasing an acceleration electrode in contact with the plasma, ions in the plasma were expelled through the neutralizer grid, and turned into energetic neutrals by colliding with the internal walls of the holes of the grid. Several Al neutralizer grids were used to study the effect of hole diameter (190-630 microns) and aspect ratio (7:1 and 10:1) on neutralization efficiency and flux. The energy distribution of the residual ions was generally bimodal and the average energy varied in the range of 50-100 eV depending on acceleration voltage and plasma gas pressure. The neutralization efficiency increased with larger holes and higher aspect ratios, approaching complete neutralization of the beam. By assuming that the energy of the energetic neutral beam is approximately the same as that of the residual ion beam, the flux of energetic neutrals was also found. The variation of flux with source operating conditions will be discussed and explained based on plasma molding inside the holes of the grid. Work supported by the Texas Advanced Technology Program.