Far ultraviolet polychromator for spectroscopic characterization of the tokamak divertor and plasma scrape-off layer

V. A. Soukhanovskii, D. Stutman, M. J. May, M. Finkenthal, H. W. Moos, J. L. Terry, J. A. Goetz, B. Lipschultz
1999 Review of Scientific Instruments  
The Plasma Spectroscopy Group of The Johns Hopkins University is developing diagnostics for spectroscopic characterization of the tokamak plasma scrape-off layer and divertor regions. A far ultraviolet polychromator has been designed for radiative divertor studies at the Alcator C-Mod and D-IIID tokamaks. Local measurements of resonant transitions of lithium-to boron-like ions of intrinsic or seeded low Z impurity elements will be performed along multiple chords around the X point. Planar
more » ... ction gratings and stacked grids will be used for dispersion and angular collimation of radiation. Phosphor wavelength converters coupled to a photomultiplier tube by an optical fiber will be used as detectors. The design provides a wavelength resolution of Ӎ10 Å, a spatial resolution of р2 cm, and an adequate photometric sensitivity. The in-vessel instrument, proposed for the Alcator C-Mod tokamak, will measure intensities of the lines at 1240 ͑N V͒, 765, 923 ͑N IV͒, and 990 Å ͑N III͒. The port-mounted polychromator at DIII-D will be able to monitor intensities of 1550 ͑C IV͒, 977, 1176 ͑C III͒, and 1335 Å ͑C II͒ lines. This, together with visible and bolometric diagnostics, should enable estimates of power losses, charge state distribution and local transport of the impurity ions in the divertor. A one-channel prototype of the C-Mod and D-IIID instruments is being built for the CDX-U spherical tokamak. Line-integrated brightnesses of the 2s -2p transition at 1550 Å will be measured and inverted to obtain C IV emissivity distribution.
doi:10.1063/1.1149409 fatcat:qyiyzyosivayli7ghswe7236km