Real-time determination of the position and shape of the plasma column from external magnetic measurements in the GLOBUS-M tokamak

A fast algorithm is elaborated for determining the position and shape of the plasma column from measurements performed with magnetic probes located outside the vacuum vessel of the GLOBUS-M tokamak. The algorithm is based on the modeling of the plasma current by movable current filaments and allows one to take into account the effect of eddy currents induced in the vacuum vessel. The algorithm was tested in a series of model discharges under conditions characteristic of the GLOBUS-M tokamak and serves now as a software component of its magnetic diagnostic system. By employing a conventional PC (Pentium 1 GHz, 200-MHz data bus), the calculation time of the plasma column parameters at one instant in time does not exceed 3 ms, which offers the possibility of controlling the plasma parameters during a discharge.