First measurement of tangential Faraday rotation of CO2 laser wave in a tokamak plasma

The first measurement of the Faraday rotation of CO2 laser wave propagating in toroidally tangential direction in a tokamak plasma has been demonstrated in JT-60U tokamak. An infrared polarimeter using a couple of photoelastic modulators has reliably detected the polarization angle of a CO2 laser wave even when incident laser intensity is varied. So far, the accuracy of the measured polarization angle is ∼0.1°. Simultaneous measurements of polarimetry and interferometry has been achieved stably. The verification of principles of the tangential Faraday rotation for electron density measurement in large tokamaks has been presented.