HOW TO UPGRADE A CONTROL-SYSTEM FOR A TOKAMAK

The TEXTOR tokamak for technology-oriented research in Julich has been in operation since 1981. Its control system consists basically of a C AMAC computer system (PDP-11) for remote control and display, linked t o programmable controllers (SlEMENS 83) for subsystem control via fibr e optic cables. Due to several reasons, an upgrade of this well-establ ished control system has become unavoidable. The main objective for th is process is to provide better availability and reliability for anoth er decade of operation and to reduce maintenance costs significantly. In this respect all CAMAC instrumentation had to be preserved complete ly. The paper describes in detail the background, design and layout of the new control system. Because upgrading an existing control system substantially differs from constructing a new system for a new device, special attention is given to the steps of achieving a smooth upgrade procedure that avoids unnecessary interferences with the TEXTOR opera tion.