Design and construction of magnetic diagnostics on NanChang spherical tokamak

The NanChang Spherical Tokamak (NCST) is a new compact tokamak (with an aspect ratio of R/a = 1.67) for exploring the merging compression by which the plasma start-up is highly efficient. In this paper, a magnetic diagnostic system is designed, calibrated, and constructed on the NCST to meet the requirements of measurements. Based on detailed testing and analysis, the reliability of the sensors is guaranteed by optimizing the support structure and installation process. In addition, high-precision positioning equipment is utilized to ensure the installation accuracy of the sensors. During the start-up phase of the NCST, plasma currents on the order of a few kiloamperes were measured despite that the commensurate signal of eddy current is also found in the conducting structure. The magnetic diagnostic system is now completely operational and meets the requirements of the physical analysis on the NCST.