Enhanced density profile resolution and equilibrium reconstruction with Compact Toroidal Hybrid interferometer upgrade*

The Compact Toroidal Hybrid (CTH) experiment investigates the physics of disruptions in ohmically-driven torsatron/tokamak hybrid plasmas. To aid in characterizing these plasmas, a three channel 1-mm, 244GHz interferometer system has been upgraded by adding a fourth channel with an independent 280 GHz source. The system provides line-integrated plasma density measurements which are used by the V3FIT code for reconstructing the equilibrium 3-D flux surfaces and density profiles of CTH hybrid plasmas. The original interferometer configuration provided only 2 independent density measurements given the symmetric placement of two chords. The new design has 4 independent measurement beams spaced asymmetrically across the plasma to maximize resolution of the density profile. New beam locations were chosen based upon a refraction study using the TRAVIS code. An overview of the new design, implementation, and initial results of experiments performed to evaluate performance will be presented.