Simulations of TRT Vacuum Vessel Effect on the Magnetic Diagnostics System Sensor Signals

The results of model numerical calculations are presented, showing the effect of the TRT vacuum vessel on the amplitudes and phases of the magnetic sensors signals, which are located on the inner and outer vacuum vessel surfaces. It is shown that the characteristic times of loop voltage sensors considerably depend on their position on the TRT vacuum vessel. Therefore, their accurate mutual matching is required, especially in the dynamic stage of the discharge, when high eddy currents are induced in the vacuum vessel. The results of numerical calculations for the case of periodic disturbances in the plasma column are presented. They showed that the vacuum vessel almost completely shields the signals of the magnetic sensors located on the outer surface of the vacuum vessel. Moreover, it affects not only the amplitudes of magnetic sensors signals, but also their phases. Numerical studies brought us to conclusion that it is of priority to install the magnetic sensors just on the inner surface of the TRT vacuum vessel.