SYSTEM FOR T-15 TOKAMAK POLOIDAL FIELD CONTROL

Abstract

This chapter describes the plasma equilibrium control concept on a T-15 facility. Control is hierarchical and is realized on three levels: (1) calculation of control programs for rather long-term series of experiments, (2) correction of control law by the experimental results aimed at compensation of program errors, and (3) real-time control to compensate occasional fluctuations. Plasma position in the chamber is stabilized by means of vertical and horizontal control magnetic fields correction. For this purpose, the system comprises subsystems supplying three coils for vertical magnetic field control, realizing slow control loops and two fast control loops in the form of special control coils for vertical field and horizontal field correction and subsystem for OH-coil supply at discharge initiation and discharge current maintenance. Plasma is controlled by the plasma current stabilization loop, vertical position control loop, and horizontal position control loop. The scheme of the plasma position horizontal control consists of fast loop affecting the dipole coil current through the fast-operating switch and a static loop affecting the closed loop by the thyristor converter voltage through the proportional-integrating regulator depending upon the dipole coil current. Thyristor converters of the control coils are connected through the voltage negative feedback and are controlled according the given programs. Vertical plasma position control is performed according to the program and by the plasma deviation from the equilibrium. The scheme consists of three feedback loops for converter voltage, OH-coil current, and plasma current.