JT-60 plasma control system

JT-60 plasma control is performed by a supervisory controller, a measurement system and by actuators such as the poloidal field coil power supplies, gas injectors, neutral beam injection (NBI) heating system and radio frequency (RF) heating system. One of the most important characteristics of JT-60 is a fully digital control system composed of mini-computers, fast array processors and CAMAC modules, which is very flexible. After an eight-year design and construction period, the system started in operation in April 1985. During three years of operation, the system has been improved many times; few troubles have been experienced in adjusting it. In this paper, the specifications of the final system, including technological aspects of hardware and software, are presented. The actual real-time control functions are explained in detail and the results are described for JT-60 outside-divertor plasmas. The emergency termination methods, which are indispensable for a large tokamak plant, are also presented. Finally, some problems to be solved on plasma control are discussed. (orig.)