JAERI-Conf 95-021

PB22
Present Status of HIMAC Synchrotron Control System
E. Takada, S. Sato, K. Noda, M. Kumada, M. Kanazawa, A. Itano ·, N. Araki,
Research Center of Charged Particle Therapy
National Institute ofRadiological Sciences
4-9-1 Anagawa, Inage-ku, Chiba-shi 263, JAPANandY. Sano, T. Togashi, H. Takahashi, M. Ogata, M. Mori, and T. Gushiken,
Accelerator Engineering Corporation
2-10-14 Konakadai, Inage-ku, Chiba-shi 263, JAPANAbstract
IDMAC synchrotron has been in operation sincelate 1993. Daily operation for irradiation of clinicaltrial have been executed satisfactorily. Present statusof IDMAC synchrotron control system 1ssummarized.
INTRODUCTION
As a medically dedicated accelerator, Beam mustbe supplied from IDMAC for treatment quite reliably.
Requirements for beam energy and intensity can varyfrom patient to patient. Research programs whichhave been carried out nights and weekends also
widens the variety. Under these circumstances,
IDMAC synchrotrons have been operated to deliver
beams for clinical trial and basic researchexperiments in a rather stable manner.
Of course, the individual hardware (magnets,
power supplies, etc.) must be able to perform very
well in order to realize stable operations. In achieving
the reliable beam supply, however, synchrotron
control system plays important part because it
integrates the functioning of synchrotron components.
Design plan and preliminary results were presented
Operationalin the previous reports.[1,2]experience and improvement plans are described inthis report.
INITIAL TRACKING CONTROL
Synchrotron control system of IDMAC has beenin operation since fall, 1993, when commissioning
began. During commissioning,[3] the most crucial
task of the control system was to assure tracking of• Public Health & Environment Dept.,
Hyogo Prefectural Government.

BM and QF/D magnets excitation, because thescheme was to set current pattern precisely matchedand to converge actual output current pattern to thepreset one via repetitive, or 'self-study', control.
Mechanism is an iterative application of thefollowing procedure: The control system sets thecurrent and voltage pattern of desired excitation to apower supply, then the system detects deviation tl I
at 1,200 Hz, or each firing pulse of thyristors, and,after averaging over several cycles, it calculates
modified voltage pattern to correct current deviations.
The calculation involves the presumed response
characteristics of the magnet & power-supply system,and tuning was done in cut and try method prior to
the beam test. Even with the pre-tuning, two
aspects remained to be answered by the beam; to find
an appropriate current setting pattern and to assure
effective convergence of the iteration.
Although we had started from the desired valuesof magnetic field and the approximate expression of
the current .vs. magnetic-field relation from actualfield measurement, it turned out that simply applying"proportional" current setting among BM and QF/D
magnets apparently suffice. Here, flat base and flat
top values of currents are given and the ramping
between them are adjusted in such a way that theratio of current value to flat top value in terms ofsurplus from flat base value at each point is kept
This is certainly lessacross BM and QF/D.
field, but moremagnetic
fromcase
theaccurate thanstraightforward and practical m operation'sviewpoint.
It was later tested with higher excitation thanoriginal230 MeV/u or most used 290 MeV/u level,
e.g., 600 and 800 MeV/u, and results were quite
successful, even the field saturation effect contributes
non-trivial extent at these higher excitation. Thus,
semi-empirical method worked well on the first
aspect of the problem: finding appropriate current-309-JAERI-Conf 95-021

setting pattern.
The second part was much more complicated andnot yet fully understood, because the power supply
itself has its own built-in voltage regulation circuitryand thus the result is a mixture of two mechanism.
However empirically, convergence is obtained foreach operational patterns without re-adjusting
parameters for iterative "self-study" procedure.
Further study is expected to exploit the feature.

files using the above mentioned procedure, whichtakes several hours.
Another evidence for stability is the fact that rf
acceleration without beam feedback signal isroutinely realized for a wide range of intensity; 5xl02
to lx10 10 ppp.[3] In all, this means that thestability and reproducibility of the synchrotron wasgood enough to meet the requirement of medicalapplication as well as research usage.

STABILITY AND REPRODUCIBILITY

SEQUENCE AND FAULT HANDLING

After the commissioning, priority of the control
was given to stable and reproducible beam supply.
Clinical irradiation is scheduled weekly from
Tuesday to Friday with accompanying dose
measurements, and beam condition should be kept
constant during the period. A patient is usuallytreated with 18 fractions that spans six weeks,although each fraction is normally 3-5 minutes
irradiation. Since the adjustment and fi?<-ation of thepatient takes typically as much as 20 minutes, beamirradiation is required to start and complete
immediately after these preparatory procedure.
In this context, it is an essential performance for
HIMAC that the accelerator complex keeps overalltuning for a long time and delivers beam of same
conditions without re-tuning. The observation at
the early stage of operation was that when theaccelerator devices were kept turned-on withoutbeam, which is stopped right after the extraction
from ion source, beam was immediately delivered to
the final focus when the beam stopper at ion source
was opened after an overnight break.
It is also confirmed that a "file" of actually tuned
operation parameters enables reproduction of thebeam, thus once parameters were well-tuned, simply
recalling filed parameters and setting those values
secure beam delivery.
At present, carbon beams of 290, 350, and 400
MeV/u are in daily use for clinical irradiation, whileother beams such as helium, neon, and silicon havebeen studied and provided for experimental research.
For these beams, we have filies of 6 MeV/u (flat baselevel), 100, 230, 290, 350, 400, 600, and 800 MeV/u
for charge-to-mass ratio c =0.5, with basicallywell-adjusted parameters.
Essentially, no finetuning is necessary for different ion species, as far as
E =0.5. For argon and other ions with E <0.5, one
or two energy points have been studied and filed.
New energy point can be developed from the existing

One of the most practiced operation at HIMAC
synchrotron is, as seen from the above, setting all
devices to a reference value obtained from the file.
This procedure can be done with a single set of touch
operation. In the early stage of commissioning toroutine operation, it sometimes got stranded and thesoftware system of synchrotron hung-up. This wasprimarily caused by inappropriate handling of thesequence in the device control computers. Althoughcorrective measures were taken, it was realized thatmomentary load can be larger than expected for someof the device controllers.
Therefore, possible
upgrade is under consideration for performanceimprovement.
It is important to locate fault condition that
occurred during beam delivery, and to identify thecause quickly. Present control system provides
error message with presumed items for each device.
Recent recurrent troubles of device level include;-decreased water-flow at magnet,-thermo-control error at power supply, and- rf cavity voltage over.
These were caused by defective hardware, andpresumably terminated with correction on theproblematic part of the hardware. On the other
hand, system problem such as communication
trouble happens, although sporadically. It does notseem to be a traffic congestion, but incompatible
implementation of the communication protocol that isresponsible, although it remains to be identified.
Meanwhile, re-setting relevant computer of device
control level can be postponed, since each device is
set to keep operating as is when link between thecontroller and higher level computer is lost.
DEVICE CONTROLLERS
VME systems with MVME-147S CPU andFDIIFDO modules function for current pattern-310-JAERI-Conf 95-021

control of synchrotron magnets and for event timing
generator rather reliably. They are operated withPDOS real-time OS. Additional work station forfile management serves also for development andtrouble-shooting tool.
In RF /BT system, peak load seems somewhat
critical, but routine operation is performed without
The rf T -clock
troubles after system tuning.
frequency was elevated to 50 kHz for smoothertransition from B-clock region and thus for smaller
beam losses. While it helped, present scheme ofmemory module operation limits flat top time shorter
than needed for 0.3 Hz synchrotron operation, thus it
returned to original 10 kHz clock.

One of theand control system performance.
setting
patternof"stream-lining"ischange
importantsequence, for both with and without synchrotron
repetition cycle time change. Another is realizationof synchronized switching of magnet and rf patterns.
These improvements will enable faster and moreindependent change of synchrotron operationalparameters such as energy, repetition cycle, etc.
Modification to facilitate new functions, e.g.,
respiration triggered beam control, ts m progress,
too.

Table 1 Processes at CS (VAX4000/300)
Name
SSMP
MDMP
FMMP
FLSP
IDCP
MDCP
DOCP
SOCP
TSCP
RECP
TCCP
SVCP
AEHP

MAN-MACIDNE INTERFACE
For man-machine interfacing, four VS31 00 VAX
Stations are used for displaying system status, beam
monitor results, current setting patterns, etc. It was
found that with original 16 MB memory
resource/station is inadequate to respond withoperator's request. Therefore, it was enhanced to32MB per station and now works basically fine.
Two stations are allocated for two rings each,and interface with operator by accepting touch-panel
input or equivalent mouse operation. Among thepanels they provide, Pattern Editing, COD, & Tune
are the special feature of the synchrotron control,
while the others are basically common with othersub-systems, i.e., Linac and HEBT. Those are File
List, Device Status, Fault/Not_Ready List, Alarm
Message List, Trend Monitors, Vacuum System,
System Layout, Profile, and Slit & FCN panels.
MAIN CONTROLThe main control, CS, is VAX4000/300 with 64
MB memory, and is managing all the sequence
operations and periodic data taking, as well as
individual device control. It has communication
with "SV", supervisory node of control system ofHIMAC accelerator as a whole. Table 1 shows theprocesses that are running for these tasks. It is now
under performance analysis to improve systemthroughput further.

ACKNOWLEDGMENT
The authors would like to thank Messrs. K.
Moriyama and Y. Kurei of Omika Works, HitachiLtd., H. Yasuda of DEC Japan, N. Tsuzuki and M.
Tornizawa of Fuchu Works, Toshiba corporation,and E. Hishitani, T. Matsumoto, and K. Takahashi
of Hitachi Zosen Corp. for continuous support andhelp.
The authors are grateful to Prof. K. Sato ofRCNP, Osaka Univ., Drs. K. Kawachi and S.
Yamada and members of Research Center ofCharged Particle Therapy, NIRS, for discussion andencouragement. Their gratitude also goes to Messrs.
K. Ueda, Y. Sato, T. Aoki, and members of AEC.
REFERENCES
1.

IMPROVEMENT PLANS
In addition to what are mentioned above, a few
items are considered for improving operationability

Function
System Self Management
Master Display Management
File and Memorv Management
File Load & Save
Independent Device Control
Monitor Display and Control
Device Operation Control
SequentialOPeration Control
Timed Sequence Control
Rotarv Encoder Control
TCPIIP Communication Control.
'SV' Communication Control
Alarm and Event Handling

2.
3.

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E. Takada et al., Proc. 9th Symp. Ace. Sci. &Tech. (Tsukuba, 1993), p.73.
E. Takada et al., Nucl. Instr. & Meth. A352, 40(1994).
K. Sato et al., Nucl. Phys. A588, 229 (1995).