The Polarimeter/Interferometer is one of the largest diagnostics in magnetic confinement fusion device for simultaneous electron density and current density measurement. Developments have been made in two key aspects of the far-infrared laser Polarimeter/Interferometer system on HL-3 tokamak. First, in laser transport simulations, a Jones-vector method accounting for rotating eigenstates via the magnetic field angle (where Bz is aligned with the laser wave-vector direction ) has been proposed. This method enables the simultaneous simulation of both the Faraday rotation effect and the Cotton–Mouton effect under realistic tokamak equilibriums. Second, a robust density profile reconstruction method has been developed and is well-suited for scenarios involving complex multi-array configurations and/or data loss caused by fringe jumping. To date, this method has been routinely used to generate density profiles on HL-3 tokamak. Guided by device developments, experiment experience and laser transmission theory, an optimized 9-channel configuration has been redesigned for more reliable operation and better Faraday rotation angle measurement. This configuration includes 5 horizontal channels and 4 oblique channels arranged on two sides of the laser tower, and will be deployed in the next HL-3 campaign.
High-frequency measurement of the interferometric phase, the Faraday rotation, and the Cotton-Mouton effect with a single detector in a far-infrared interferometer-polarimeter