OPERATIONAL LIMITS IN TOKAMAK MACHINES

Different operational limits of tokamaks are reviewed. The finally lim iting processes are hard or soft plasma disruptions or a strong x-ray source. The underlying events are explained as far as the physical cau ses are known. Treated are the density limit, the low- q-limit, the ru naway limit, the beta-limit and the vertical displacement limit. In ad dition, the spontaneous MHD-instability and a hollow temperature profi le situation are presented. The graphical displays are experimental re sults from the TEXTOR tokamak.