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Abstract: A real-time profile control system based on PCI-bus modules has been installed in the existing plasma control system (PCS) to control high performance plasmas. In profile control, pre-programmed profile reference data, which are two-dimensional, must be manipulated as the other mono-dimensional pre-programmed reference data such as plasma current in the discharge parameter set-up and in the post-discharge data archiving process, to re-use of the existing man–machine communication tools. An preprogram algorithm number was introduced to allow the change not only of control gains but also of control algorithm during a discharge, providing flexibility and extensibility to cope with future requirements coming from control studies that are now in progress. This system has been successfully applied to safety factor profile control by lower hybrid radio frequency heating system. [Copyright &y& Elsevier]

The old discharge control system (DCS) with HIDIC-80E mini-computer has been replaced by a control system with a unix workstation and a VME-bus system. Functionally, the workstation performs message communication with VME controller on the network, data processing using plant data and data acquisition. The commands and receiving the status data in real time. The new DCS is flexible for system extension and able to quickly respond to various requirements of software modifications. The data acquisition speed has been improved by almost a factor of two over the old one. Troubles and countermeasures experienced in the replacement work are also presented. [Copyright &y& Elsevier]

Abstract: Real-time processor, RTP is a basic subsystem in the JT-60 data processing system and plays an important role in JT-60 feedback control for plasma experiment. During the experiment, RTP acquires various diagnostic signals, processes them into a form of physical values, and transfers them as sensor signals to the particle supply and heating control supervisor for feedback control via reflective memory synchronization with 1ms clock signals. After the start of RTP operation in 1997, to meet the demand for advanced plasma experiment, RTP had been improved continuously such as by addition of diagnostic signals with faster digitizers, reducing time for data transfer utilizing reflective memory instead of CAMAC. However, it is becoming increasingly difficult to maintain, manage, and improve the outdated RTP with limited system CPU capability. Currently, a prototype RTP system is being developed for the next real-time processing system, which is composed of clustered system utilizing VxWorks computer. The processes on the existing RTP system will be decentralized to the VxWorks computer to solve the issues of the existing RTP system. The prototype RTP system will start to operate in August 2008. [Copyright &y& Elsevier]

Abstract: The large tokamak fusion device JT-60 is expected to explore more advanced tokamak discharge scenarios toward the ITER and a future power reactor. Since various experimental issues are to be adequately discussed, and possibly to be solved in JT-60, the plasma real-time control system has been drastically improved with remodelling in hardware as well as in software. To satisfy the requirements, a “multiple networks” structure is employed as a basic principle of the remodelling. Distributed processors for diagnostics, actuators, and supervisory controllers are linked through a reflective memory (RM) network for fast, real-time communication. Similarly, advanced and complex calculations to reproduce plasma shape and profiles are performed by several processors connected to the same RM network. In this report, we discuss the developments to improve the JT-60 plasma control and data processing systems. In addition, a future plasma control system leading to a standard design for a power reactor is outlined, which is based on the 20-year plasma operation experience. [Copyright &y& Elsevier]

The JT-60U control system, composed of a UNIX-based workstation and a VME-bus system, has been successfully performing advanced plasma control for the JT-60U plasma discharges. Various hardware modifications and advanced plasma control algorithms have been continuously integrated into the JT-60U control system since its upgrade in 1991. The ZENKEI, the supervisory control system, has been entirely converted from its original 16-bit minicomputers and CAMAC system to the combination of a workstation and VME-bus system linked through an Ethernet network. The plasma equilibrium control system utilizes a full VME-bus system composed of three DEC alpha CPU modules that are currently running at control cycle times of 250 μs. The parameters for plasma equilibrium control are calculated by a newly developed real-time plasma shape calculation and reconstruction system. These parameters are fed to the plasma equilibrium control system synchronized by 250-μs clock pulses. To progress toward the advanced plasma control concept, which includes adoption of a global plasma parameter control algorithm and suppression of MHD instabilities, improvements were extensively consolidated into the plasma control system (PCS). Currently, additional modifications of the JT-60U control system have extended the pulse duration of the discharge without a major change in JT-60 equipment. [Copyright &y& Elsevier]