JAERI-Conf 95-021

PB21
Control system of a high energy beam transport system of HIMAC
M. Torik:oshi, E. Takada, S. Yamada, H. Ogawa, K. Noda, T. Kohno*, J. Matsuura**,S.Kobayakawa**, F. Sasaki***, K. Okumura***, S. Namai***, Y. Ishikawa***
National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263, Japan*Tokyo Institute of Technology, 4259 Nagatsuda, Midori-ku, Yokohama 226, Japan**Mitsubishi Electric Corporation, 325 Kamiya-cho, Kamakura, Kanagawa 247, Japan***Accelerator Engineering Corporation, Konakadai, Inage-ku, Chiba 263, Japan

Abstract
The control system of the high energy beamtransport system of HIMAC consists of a UNIX computer and a large scale interface system. Lengthy procedures,such as start-up Or shutdown all the devices, can be doneby only one ci>mmand followed by sequential proceduresin the interface system. Man-machine interface is concentrated on a console to operate easily. Total system eventually realizes the simplified operation and highly reliable
performance. In this system, however, a special operation is required because of radiotherapy.

Introduction
The Heavy Ion Medical Accelerator in Chiba(HIMAC) is a complex of an injector linac cascade, two
synchrotron rings, a high energy bean1 transport systemand. an irradiation system1.2). Each system is called subsystem, and is controllable independently. Anothercomputer system, a supervisor system, is monitoring all
the sub-systems, and also working as an interface between the sub-systems.
Beams extracted from the rings are transported tofour irr~iation ports of three therapy rooms, and threeexperiment ports through the high· energy beam transport(HEBT) lines. The constituents of the ~BT system are16 bending magnets, 69 quadrupole magnets, 39 steering
magnets, their power supplies including those for thesuppression coils for residual magnetic field and correction coils, 30 beam monitors, 16 vacuum units, 16
NMR sets and many other devices. The HEBT control
system was required to have functions of simplified andrapid operation of the devices, software interlocks to keep
patients safe and highly reliable performance because of a
medical machine. The medical use also requires a special
operation related with beam irradiation for treatment. In
this paper, features of the system and its operation arereported.

The HEBT control system
The control system is divided into the main com-puter system and the interface system as shown in-Fig.l.
MELCOM70-MX570011 (Mitsubishi Electric Corporation) is in use as the main computer. The interface
systeni, called MELTAC-RIO system, connects thecomputer _and most devices of the HEBT. The computerhas other interface ports of GPIB and PIO. GPIB andPIO are used for communication with NMR devices andwith an interlock system, respectively. There are two·sets of console as man-machine interface. These consoles
are corresponding to beam lines from the upper and lowerrings, respectively. Each console has 20" and 14" displays, and 3 rotary encoders. The displays are equippedwith touch-panels. The computer system is connected tothe supervisor system with LAN (Ethernet). Radiationdose is monitored not only at the irradiation control room
but also on the consoles of the HEBT system through aLAN installed exclusively for monitoring the dose.
The interface system, MELTAC-RIO, consists ofa communication unit and a group of distributed remotel/0 (RIO) units. The communication unit works toarrange and manage data flow from the computer to RIO,and vice versa. Data from RIO is reformatted to betransmitted to the computer cyclically in every 200msec
interval. The transmission cycle of 20<Jmsec is enoughfast to monitor the system status. The computer interrupts the communication unit to send the commands (ITmessage) to operate the devices. The computer can also
send a file including parameters such as maximum andminimum currents, and repetition number for initializatj.on, thus complicated procedure can be handled. The
communication unit is connected to the computer with adata bus, MDWS-60.
Ten RIO units are distributed in this system asshown in Fig.l. Each unit is connected to various
devices through three kinds of data bus, PIO orMELSECNET or 1/0 bus. The PIO connects the magnet
power supplies and the relevant RIO units. DI and DO
cards mounted in the units receive and transmit digital
signals based on contacts or open collectors. In order toinitialize the magnets, the RIO units sequentially control-306-JAERI-Conf 95-021

General purpose LAN,---------------1I'ln"-''·-'···
IIII

ComputerIII

Monitoring LANMELTAC-C RIO System- Co~wlic~wn~nit~----------------1---------------------~

I

1-.-------.---------.--------.---------~r-------------------------------~~~~~~~~--~~~~~----~

MagnetPower
Supply(13)MagnetPower
Supply(20)Power
Supply(20)

Power
Supply(16)Power
Supply(10)Power
Supply(38)I
I

Vacuum Monitor Monitor Neutron Shutters
Timing System,LCP
System LCP
etc.
(2)
(2)
LCP
(4)

Fig.l Schematic diagram of the HEBT control system

the power supplies according to the parameters of theinitialization as mentioned above. Maximum 30 magnets can be initialized at the same time by only one
command. Therefore, an arbitrary number of magnets canbe initialized in short time by repeating the command.
Local control panels (LCP) are distributed on the floor of
the beam lines for the operation of the beam monitors
and vacuum system, because it is necessary that the beam
monitors and the vacuum system are locally operated intheir maintenance. The devices of the vacuum system arecontrolled by a programmable logic controller (PLC)
installed in a LCP. Four LCP's are linked in a circle, andthe master LCP is connected to the RIO unit with theMELSECNET. The MELSECNET is exclusively designed for communication of the PLC. In case of thebeam monitors, the DI and DO cards and buffer memories
are mounted in the LCP's, not in the RIO units. Onlymaster cards are installed in the RIO units to communicate with the LCP's through the 1/0 bus.
This MELTAC-RIO system deals with a large
amount of data such as magnet currents, magnet status,pressure in beam ducts, beam profiles, and of operation
information such as power supply ON/OFF commands,
magnet initialization commands and so on. In order torealize rapid operation and monitoring, this system are
cyclically processing data under a single task software
using cpu's of i-80386. The cycle runs every IOOmsec
interval in the communication unit, and 50-70msec in theRIO units. The data is transmitted between the RIO
units and the communication unit cyclically through databuses, called SE-BUS3. There are three groups of theSE-BUS3, in order to reduce the amount of data of eachdata bus, and realize a rapid response. The data buses are
summarized in Table 1, all of them being Mitsubishi-307-JAERI-Conf 95-021

Table 1 Summary of Data Bus
Data Bus
Medium ofMDWS-60

SE-BUS3

Coaxial cables

Optical fiber

Optical fiber

Optical fiber

cablescablescablesTransmission
Transfer Rate
Method ofTransmission

15.36Mbps
CyclicFile
IT-Message

2M bpsCyclicElectric Corporation standard. Note that the cyclic dataprocess and data transmission can make a maximum loadof the computer independent of the amount of data, andrealize stable and reliable performance.

Operation and control
Beam tunings for the horizontal or vertical course
can be done independently at each console. The devicesof the HEBT system are hierarchically classified with"systems", "groups" and "blocks", as in other sub-systems3). A block unit uniquely corresponds to a beamcourse. So the block classification makes it easy toswitch the beam course from one to another.
The operation of starting up the whole HEBT
system for new beam conditions is performed with thehelp of an operation parameter file. The file includes thesetting values such as excitation currents of the magnets,
high voltage of the beam monitors. In this operation,
the magnets are initialized before excitation, and the beam
monitors become ready to use by being applied suitable
voltage. In about five minutes, devices are ready after theoperation. Then a beam course is selected before tuning
beam. Beam tuning is done for all the beam courses
connected to the scheduled therapy rooms in advance ofthe treatments. It takes about 25 minutes for relevantbeam course. Since the beam course selection is carriedout by only exciting the switching magnets, the therapy
room can be changed by only switching the beam coursein 5-7 minutes.
Only medical operators are allowed to open thebeam shutters in clinical patients irradiation. On theother hand, operators of the accelerator must handle theshutters to tune the beam. In order to prevent wrong
operations, we allow opening the shutters from one
console at a time, either HEBT or irradiation console.
Both control systems can always close the beam shutters.
Furthermore, the operators of either control system canMELSECNEI'

I/O BUS

1.25Mbps
CycliclMbps
Polling/Selecting Method

command not to change any operation parameters ofupstream sub-systems during the treatments.
Software interlocks close or prohibit from opening
the beam shutters under a few conditions of the HEBT
system, in order to prevent unwanted irradiation ofbeams. The conditions are as follows. (1)No beamcourse is selected. (2)Magnets and/or power supplies ofthe selected beam course are out of normal conditions.
(3)Any gate valve of the beam course is close. (4)The
computer or the supervisor system does not work.
(5)The computer is disconnected from the supervisor
system. Therefore the software interlocks exclude wrong
operations or abnormal conditions of the HEBT system.

Summary
In the HEBT control system, a large scale interface
system, and its single task processes realize simplified
and rapid operation with stable performance. All theoperation functions are put together on the displays
equipped with touch-panels and the rotary encoders as
man-machine interfaces. These features make the operators possible to operate easily and uniformly. The software interlocks are excluding wrong operations due tohuman errors or machine failures. Overall the HEBT
control system is reliable and easy to handle, and shows
good performance.

References
1. K.Sato et al., "Status report on HIMAC", Proc. 4thEuropean Particle Accelerator Conf., London, 1994
2. S.Yamada, "Commissioning and performance of theHIMAC medical accelerator", Particle Accelerator Conf.,
Dallas, 1995, to be published
3. T.Kohno et al., "Control system for HIMAC injector", Proc. of the 7th S ymp. on Accel. Sci. And Tech.",Osaka, 1989, pp.246-248-308-