The profiles of the axial and radial momentum fluxes lost to the radial wall are experimentally investigated in a helicon source by using a momentum vector measurement instrument, where two gas injection configurations from the upstream of the source tube and from the downstream open source exit are tested. It is observed that the axial position of the maximum density is shifted to the source exit side for the downstream gas injection, compared with the upstream one. The measurement shows that the axial momentum flux transferred to the radial wall for the upstream gas injection is larger than that for the downstream gas injection, indicating that the axially accelerated ions are lost to the source wall. It is demonstrated that the loss of the axial momentum can be reduced by injecting the neutral gas near the open source exit, i.e., for the downstream gas injection.
ASJC Scopus subject areas
- Condensed Matter Physics