Construction of the Central Control System for the Large HelicalDevice (LHD) Fusion Experiment
K. Yamazaki, H. Yamada, K.Y. Watanabe, K. Nishimura, S. Yamaguchi,
M. Shoji, S. Sakakibara, J. Miyazawa, Y. Taniguchi, H. Ogawa,N. Yamamoto, T. Kato, T, Tsuzuki and O. Motojima
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-shi, Gifu-ken 509-52, JapanThe world’s largest superconducting helical fusion facility, the Large Helical Device (LHD), is in the final stageof the 8-year construction schedule at the National Institutefor Fusion Science (NIFS), Toki-City, Japan. For flexible
physics experiments and reliable engineering operations ofthe LHD machine, the Central Operation and Control
System (COCOS) has been designed and constructed. A
conventional hard-wired logic system has been used
between COCOS and several tens of sub-systems inaddition to the FDDI computer network communication.
The Windows-NT client/server system is adopted as manmachine interface in addition to a Unix data monitoring
system using a WWW/Java program. The construction of
COCOS will be finished in December, 1997, and thefirst plasma operation will be started at the end of March,1998.
1 Introduction
Fig.1 Schematic view of LHD(Large Helical Device)

Helical systems have inherent merits of steady-state
operations for fusion reactors. The Large Helical Device(LHD)[1-3] (Fig.1), the world’s largest superconducting
helical fusion machine with a major radius of 3.9 m, a
minor radius of 0.6 m and magnetic energy of 1.6 GJ, is
now in the final stage of the 8-year construction scheduleat Toki-City, Japan.
One of the main objectives of the LHD project is todemonstrate steady-state operations of a helical fusion
system extrapolatable to a future fusion reactor and to
study toroidal fusion plasma behavior. The construction ofall the superconducting coils has already been completed,and the cryostat and the plasma vacuum vessel have been
installed on the final location.
In April 1996, we started the construction of the Central
Operation & COntrol System (COCOS), the control data
monitoring system and the uninterruptable power supply(UPS) system for the LHD Control Building. In addition tothis central control system, about 50 sub control systems
are being prepared. These systems are composed of avariety of computers such as UNIX engineering workstations, Windows-NT client/server personal computers,
VME computer boards with real time OS and programmable logic controllers (PLC).
In this paper, the current status of the LHD central
control system COCOS will be presented.

mode, coil cooling mode, coil operation mode and plasma
experiment mode (Fig.2). These modes determine thepersonnel entrance requirements with respect to electricity
and vacuum hazards, magnetic field hazards and possible
radiation exposure. Its sequential control is carried out by
the COCOS central slow sequence and fast timing system.
For simplifying the construction of a reliable controlsystem, we decided firstly to use hardwired connection
between the COCOS and the sub systems. In particular, theprotective interlock system requires this for its simplicity
and reliability. Secondly, we added a flexible LHD Manmachine System (LMS) based on Windows-NT toCOCOS.
The superconducting helical and poloidal magnets
should be operated safely and reliably, and the plasma
experiment require flexibility. These magnets will beoperated for about 10 hours per day, and the rate of shortpulsed plasma operations with 10 second duration will betypically 50 - 100 shots per day. The LHD is also going
to be operated in steady state mode (more than 1 hour pulselength) and requires interactive control of the machine andthe plasma. Advanced control methods such as fuzzy logic,
neural network, genetic algorithm (GA) or chaos control
schemes will be adopted to perform flexible and reliable
LHD operations.

2 Operation scenario

3 LHD control system [4-5]

The LHD machine operation is classified into six modes;
shut-down mode, facility operation mode, vacuum exhaust

3.1 Concept of the LHD central control system

Fast Timing Control
Slow Sequence Control
Operation Mode Management

The initial LHD operation should be carried out quickly
And reliably. A central board with hardwired prograCENTRAL CONTROL SYSTEM (COCOS)

Wall Conditioning

Plasma Experiment
Coil Operation
Coil Cooling

Vacuum Evacuation
Shut-down

Facility Operation

Reliable Operation

Flexible ExperimentCentralOperation
ConsoleMan MachineInterfaceComputer

Sequence
Control andInterocks(PLC)

Fast Timing(VME)

Hard-wired

OpticalControl
Information
Network(FDDI Switch)LAN

SUB-SYSTEMS

Fig.2 LHD operation modes
The current goal of the LHD project is to produce a firstplasma as soon as possible, and as reliably as possible. On
the basis of these operation scenarios, the designed control
system is composed of the central experimental control
system and several subsupervisory facilities which areconnected by the FDDI-LAN in addition to hard-wired
interlock and sequence control. The construction of themain unit of COCOS was started in April, 1996 based on
the following design philosophies;(1) flexibility for physics experiments,(2) reliability for the large engineering machine and(3) expandibility for the central control system.
The design philosophy (1) requires a human-friendly
man-machine interface and advanced real-time plasma
control systems, item (2) requires reliable, hardwired,protective interlock systems, and requirement (3) leads todistributed and modularized control/ monitoring systems.
A conventional hard-wired logic system has been used
between COCOS and several tens of sub-systems inaddition to the FDDI computer network communication(Fig.3).
3.2 History of LHD control system studies
At the beginning of the LHD proposal (about 10 yearsago), the control system was expected to be based on acentralized control “process computer”. About 5 years later
a UNIX engineering work satiation with VME computers
was proposed. Now, some client-server systems using
Windows-NT have been added for control and dataacquisition. These central systems and more than 50 subsystems are now connected by FDDI and ATM networks.
3.3 Architecture for LHD control system
COCOS is composed of the central control unit (centralconsole, central control board, central control computer,and the timing board), the torus instrumentation unit (torus
instrumentation computer board and protective interlockboard), the LHD Man-machine System(LMS), the control
data acquisition system, the LHD experimental LAN andthe uninterruptable power supply(UPS) systems. Thesesystems use a variety of computers such as UNIX
engineering work stations, Windows-NT personal computers, VME computer boards with real time OS (VxWorks)
and programmable logic controllers (PLC).
Figure3 shows the details of this system architecture.

LHD

Fig. 3 LHD central control system concept
mmable logic controllers will be used for this initial
operation. This is particularly importance for the protective
interlock system in COCOS.
The fast timing system with 64 channel optical signals( accuracy: 1 micro-second, set-up interval: 1 ms ~ 10 hr)
will be distributed to sub-systems.
The feedback control for plasma current, position andcross-sectional shape will be carried out using intelligent
VME control systems, such as applications of fuzzy logic
and neural networks in addition to standard PID plasma
control algorithms. Related R&D programs have been
carried out.
3.4 Data monitoring systems for machine and plasma
For machine supervision one of the data monitoring
systems is based on Windows-NT using a 1300 channel
VME board [4-5]. The LHD Fast Data Monitoring
system[6] with a 512 channel VME and a UNIXworkstation was also constructed. Full Java computer
software in WWW Browsers was used in the latter system
which will be extended to 4000 channels. To manage thedata, a relational Data base was used in this system.
On the other hand, the plasma data acquisition system[7]using CAMAC modules is now under construction basedon Windows-NT. The large super-computer system fortheoretical analyses using experimental data are connectedto the experimental control computer by the interlaboratory FDDI-LAN and ATM system.
4 Construction of the LHD control building and experimental schedule
In our new site (Toki-city, Gifu-prefecture), the construction of the main experimental hall of the LHD Building
was finished in August, 1995, and the superconducting coilwinding machine for helical coils had been operated. The
construction of the largest superconducting poloidal coilhas also been completed in this experimental hall. The
lower cryostat, the electric power supply for poloidal coils
and the Helium refrigerator were installed there. Both themachine and the building construction are on schedule.

150 inch
DisplayCentral
Supervision
Panel

NIFS Campus LAN

Large-ScaleSimulation
Cluster

LHD COCO System(C entral O peration & Co ntrol)

ATMCentralOperation
ConsoleCentral Computer

LHD Man-Machine
System (LMS)ATMATM

Experimental Analysis
Sub-Cluster

FDDI Switch

RouterPlasmaDiagnostic
Control
SystemsTiming(VME)VME

LHD Experimental
Cluster¥¥¥

Experimental Control
Sub-Cluster

Sequence
Control(PLC)

ResearchBasis
Cluster

Torus Supervison
Computer

Plasma Data Aquisition
Sub-Cluster

Diagnostics Control
Sub-Cluster

RouterTorus Control
Sub-Cluster

PlasmaControl

CoilElec.P.S

CryogenicSystem¥¥¥¥ ¥Vacuum
SystemPlasmaDiagnostic
Systems
PlasmaHeating

Utilities

TorusSupervision
SystemProtectiveIntelockSystem‚k‚g‚c Main Torus

Optical Network
Optical Timing Signals
Control Signals
Interlock Signals

Fig. 3 LHD control system
The LHD Control Building with the main control hall
was completed in November, 1996. The plasma
experiments will be started at the end of March in 1998,
and a variety of experiments using this SC helical device
will be performed.

The construction of the LHD Central Operation &COntrol system ( COCOS) has been started in April, 1996.
The design philosophies of COCOS are (1) flexibility,(2) reliability and (3) expandibility; namely (1) humanfriendly man-machine interface and advanced real-time
plasma control; (2) reliable hard and soft interlocks; and (3)distributed and modularized control system.
The LHD Control Main Hall was completed, and theconstruction of the COCO system will be finished on
December, 1997. The LHD plasma operation will bestarted at the end of March, 1998.
References

Fig.4 Central control system COCOS
installed in the main control hall
5 Summary[1] A. Iiyoshi et al. Phys. Plasma 2(1995) 2349.
[2] M. Fujiwara et al., J. Fusion Energy 15 (1996) 7-154[3] O. Motojima, et al., Fusion Engineering and Design 20(1993) 3-14.
[4] K.Yamazaki et al., Nucl. Instr. and Meth. in Phys. ResA 352(1994) 43.
[5] H. Yamada, et al., Fusion Technology 1996, Elsevier
Science B.V. (1997) pp. 945-948.
[6] S. Yamaguchi et al., J. Plasma and Fusion Research 73(1997) pp.335-342 (in Japanese).
[7] H. Nakanishi et al., J. Plasma and Fusion Research 72(1996) pp.1362-1369 (in Japanese).