Method of neutral density determination near the X-point in DIII-D

摘要

A new method for determining the density of neutrals near the X-point of a diverted plasma is described. Code calculations have predicted that the neutral density peaks poloidally near the X-piont and there is evidence that neutrals play a role in the L-H transition and in damping the plasma rotation. The new method uses D(sub (alpha)) data from a tangentially-viewing video camera calibrated by a vertically-viewing photomultiplier. These data, combined with electron temperature and density measurements from the divertor Thomson scattering (DTS) system, provide sufficient informatino to determine the neutral density in the X-point region of DIII-D. Preliminary results show neutral densities above the X-point are order 10(sup 10)--10(sup 11) atomscm(sup 3). The diagnostics used to determine these neutral densities, the data analysis method, and preliminary results are described in this paper.