Passage of a low-density plasma through transparent grids

Equations of two-fluid transient collisionless gas dynamics are used to consider extraction of ions from a low-density laser plasma in connection with laser isotope separation by the AVLIS (atomic vapour laser isotope separation) method and with mass-spectroscopic analysis of the elemental composition of a laser spark. It is shown that during passage of a laser plasma through ion-accelerating grids the ion current is blocked and the plasma is reflected by the grids. A strong field, which breaks up the plasma in the gaps between grids, is insufficient to transport ions across a grid. It is proposed to use a remote electrode under a small electron-extracting potential in order to increase strongly the efficiency of ion extraction in weak fields.