Plasma displacement calculation for TT-1 device based on multiple magnetic probes fitting methods

Abstract

The HT-6M device has been upgraded and rebranded as the Thailand Tokamak 1 (TT-1), which has been reinstalled and is now operational in Thailand. In tokamak discharge experiments, precise monitoring of plasma position and the implementation of effective feedback control are essential for ensuring the stability of the high-temperature plasma. Accurate calculation of plasma displacement is critical to the success of the experiment. This paper presents a method for calculating plasma displacement through a multi-probe fitting technique, utilizing data from twelve magnetic field probes. Initially, magnetic field signals generated by the plasma are collected via multiple magnetic field probes installed poloidally outside the vacuum chamber, coupled with corresponding signal conditioning and integration circuits, with each probe undergoing calibration. Subsequently, during tokamak discharges, interference signals from the toroidal field coils, ohmic heating coils, and vertical field coils are generated by the magnetic system and corrected through a detailed calibration process. Lastly, the distances between the probes and the plasma are computed using data from the magnetic field probes, which are arranged in a circular configuration. The least squares method is employed to formulate a residual equation for fitting the actual plasma displacement. The effectiveness of this approach was validated through experimental data from the TT-1 device, demonstrating that the calculated plasma displacement exhibits a consistent trend with the CCD video recordings. This multi-probe displacement calculation method enables precise control of plasma displacement, thereby providing theoretical support for tokamak experiments and establishing a foundation for future experimental operations and data analysis.