Design and Development of Sensors for Eddy Current Experiments on a Toroidal Vessel

Abstract

Eddy currents are produced due to the change in position of plasma during the plasma instabilities in a tokamak. The presence of a high magnetic eld due to the toroidal eld coils, induces electromagnetic forces on interaction with the induced eddy currents. It is essential to know the value of induced currents and changes in plasma positions that cause them, so that the mechanical structure can be designed that can withstand the electromagnetic forces induced by eddy currents. Rogowski coil and Mirnov coil are the two diagnostics that are used in tokamaks for currents and magnetic measurements respectively. The project work is the design and devel- opment of these diagnostics and use them for eddy currents experiments on a toroidal vessel. In the rst part of the project work a non-intrusive current measuring sensor, Ro- gowski coil, is designed and developed. A test bench has been developed in order to calibrate and test the coil. Experiment setup to measure induced currents on a toroidal vessel has been developed. Two Rogowski coils are used for obtaining the value of vessel eddy currents. Comparison of the experimental data of induced cur- rents with ANSYS simulation results has been made. In the second part of the project work, Mirnov coil has been designed and developed. A square Helmholtz coil system is used for coil calibration. The coils with di erent di- mensions has been calibrated and used in the eddy currents experiment. Flux density from di erent locations across the toroidal vessel were obtained by calibrated coils. Flux density distribution across the entire vessel was thus known experimentally. The current density distribution across the entire vessel was obtained from ANSYS sim- ulation. Since current is directly proportional to ux density, the experimental data was compared with the simulation results.