High Resolution Spectroscopic Diagnostic for Divertor and Scrape-off Layer Neutral and Impurity Emission Measurements in the National Spherical Torus Experiment
Authors: V.A. Soukhanovskii, A.L. Roquemore, C.H. Skinner, J. Menard, H.W. Kugel, D. Johnson, R. Maingi, S. Sabbagh, and F. Paoletti
Date of PPPL Report: July 2002
Presented at: the Fourteenth Topical Conference on High Temperature Plasma Diagnostics, 8-11 July, 2002, Madison, Wisconsin, USA. Proceedings published by Review of Scientific Instruments 74 No. 3 (March 2003) 2094-2097.
The National Spherical Torus Experiment (NSTX) boundary physics program presently focuses on edge power and particle flow optimization and control in beta greater than or equal to 25% long-pulse L- and H-mode plasmas with high harmonic fast wave heating power up to 6 MW and neutral-beam injection power up to 5 MW, with the emphasis on the edge physics implications resulting from the low aspect ratio geometry. To address the particle flux measurements in the divertor and plasma scrape-off layer (SOL), two spectrally filtered one-dimensional charged couple device cameras have been fielded. The cameras utilize 2048 pixel 12-bit Dalsa CL-C6 arrays, f = 85 MM lenses, and Dl = 1.5 nm bandpass interference filters. Both cameras provide mm spatial resolution, sub-ms temporal resolution and are spatially and photometrically calibrated. Midplane SOL and divertor brightness profiles of C III and deuterium species have been obtained in L- and H-mode phases of center stack limited and diverted plasmas. The equilibria reconstructed by the EFIT code are found in good agreement with the optical measurements. In-out asymmetries in divertor recycling and carbon fluxes have been observed in L- and H-mode plasmas. No strong systematic dependence of inboard brightness profiles and divertor particle flux in-out asymmetries on magnetic boundary configuration has been found. The analysis of neutral recycling and impurity fluxes using the two-dimensional multi-fluid code UEDGE is in progress.