Effect of background polarized light in magnetic equilibrium reconstruction*

In addition to the multi-channel motional Stark effect (MSE) diagnostic system for the Korea Superconducting Tokamak Advanced Research (KSTAR), the polychrometer-based MSE system with the same number of sight lines has been adopted for the simultaneous measurement and subtraction of the background polarized light.  Two independent MSE systems are compared to estimate the effect of the background polarized light with intermediate plasma densities on the magnetic equilibrium reconstruction.  The systematic errors introduced from the background polarized light evaluated from this comparative studies can be extrapolated for high-density plasma discharges such as those in ITER.