Characterization of Coherence Imaging Instruments for the CTH and W7-X Experiments*

Two dimensional profiles of line-integrated impurity emissivity and velocity in the Compact Toroidal Hybrid (CTH) experiment are obtained with Coherence Imaging Spectroscopy (CIS), a polarization interferometry technique with fixed delays. The 2D measurement output provided by a recently developed analysis routine, is necessary for the non-axisymmetric geometry of CTH plasmas. Bench tests of the CIS instrument demonstrate externally applied magnetic fields induce spurious flows of order 1 km/s for field strengths of up to 200 G irrespective of field direction. Additionally, two new CIS instruments designed to investigate the 3D physics of the W7-X island divertor by providing ion impurity flow measurements in orthogonal directions are fully operational. Further, a continuously tunable laser over most of the visible region now provides immediate and accurate calibrations of both CIS systems during W7-X plasma operations.