Development of a robotic calibration system for the motional Stark effect diagnostic on the EAST tokamak

The Motional Stark Effect (MSE) diagnostic is one of the key methods for measuring the current density distribution in magnetically confined fusion plasmas. On the Experimental Advanced Superconducting Tokamak, a calibration system based on a collaborative robot has been developed to enhance the accuracy of the calibration work during the maintenance period. This robotic calibration system uses a camera to automatically capture the observation sightlines and generates polarized light with an accuracy of ∼0.5 mdeg. Additionally, it records the MSE diagnostic response at each angle of polarized light perpendicular to the sightlines. This process supports the rapid sightline geometric calibration and facilitates the collection of polarization responses across various spatial positions and angles, even within the complex environment of the tokamak vacuum vessel. The new robotic calibration system significantly improves measurement precision, reduces calibration time, and provides high-quality calibration data. The maximum fitting deviation of the polarization angle has been reduced to less than 0.2°.