First measurements of electron temperature and density with divertor Thomson Scattering in radiative divertor discharges on DIII-D

Abstract

We have obtained the first measurements of n{sub e} and T{sub e} in the DIII-D divertor region with a multi-pulse (20 Hz) Divertor Thomson Scattering (DTS) system. Eight measurement locations are distributed vertically up to 21 cm above the divertor plate. Two-dimensional distributions have been obtained by sweeping the divertor plasma across the DTS measurement location. Several operating modes have been studied, including ohmic, L-mode, Elming H-mode, and Radiative Divertor operation with puffing of D{sub 2} and impurities. Mapping of the data to either the (L{sub pol}, {phi}) or (R, Z) planes with the EFIT equilibrium is used to analyze the 2D profiles. We find that in ELMing H-mode: n{sub e}, T{sub e}, and P{sub e} are relatively constant along field lines from the X-point to the divertor plate, especially near the separatrix field line. With D{sub 2} puffing, the DTS profiles indicate that T{sub e} in a large part of divertor region below the X-point is dramatically reduced from {approximately}30-40 eV in ELMing H-mode to 1-2 eV. This results in a fairly uniform low-T{sub e} divertor, with an increased electron density in the range of 2 to 4 x 10{sup 20} m{sup -3}. Detailed comparisons of the spatial profiles of n{sub e}, T{sub e}, and electron pressure P{sub e}, are presented for several operating modes. In addition, these data are compared with initial calculations from the UEDGE fluid code