Bp 188 en
Simulation of the control system for plasma positioning in COMPASS tokamak
Author: Radek Beňo
Themonuclear fusion in tokamaks is a promising global power source for mankind with practically unlimited fuel supply, if some residual physics and technological problems will be solved. One of them is ability to control electric current, density, position and shape of the plasma discharge. The vertical position is especially difficult because its intrinsically unstable on a fast time scale for plasmas vertically elongated. This is the case for the tokamak Compass, currently under reinstallation in Prague. The elongation is performed by poloidal coils, producing asymmetric forces, yielding vertical instability. In the first part of this Bachelor thesis, I derive step by step a model of the vertical plasma position control system in tokamak Compass.
Important is the voltage amplifier which dynamic properties are modified by current feedback, and the regulator of outer loops. Among several tested controllers, I identified the PD controller as the best. Tuning of both the current feedback and the PD regulator is also described. In the second part of the thesis, I focus on computation of the main and mutual inductances of all poloidal circuits of the tokamak Compass. This work is useful for verification of the circuit connections, based on original documentation from the United Kingdom where Compass used to operate. In addition, we suggested a small modification of the connection, improving thus the reaction time of the vertical control system.