Stabilization of unstable vertical position of plasma in T-15 tokamak. I

Consideration was given to the design and mathematical modeling of the stabilization system for unstable vertical position of plasma in the T-15 tokamak (Institute of Tokamak Physics, National Research Centre “Kurchatov Institute”). For suppression of vertical instability of plasma, the poloidal systems of vertically elongated tokamaks were analyzed with the aim of detecting the most efficient positioning of the winding of the horizontal magnetic field (fast winding) in the T-15 tokamak. The controllability domains of vertical shift of the plasma magnetic axis were estimated for various arrangements of the fast winding (i) outside the toroidal winding, (ii) between the toroidal winding and the vacuum chamber, (iii) inside the tokamak vacuum chamber. Part I considered the linear control system for vertical plasma position where the fast winding is located outside the tokamak toroidal winding. For the given configuration of the poloidal system, the control system of the T-15 tokamak was shown to be inherently unstable. Inherent system stability is attained by using a multidimensional control system where all windings of the central solenoid and the windings of the poloidal field are used to control the vertical plasma position and the current in the fast winding.