The I lth Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

Progress in HIMAC Accelerator Operation
Yoshinobu SANO, Kazuhiro VEDA, Hirotsugu OGAWA, Toshitaka FUKUSHIMA,Katumi OKUMURA
Accelerator Engineering Corporation (AEC),
Eiichi TAKADA, and Satoru YAMADA
National Institute of Radiological Sciences (NIRS),
4-9-1, Anagawa, Inage, Chiba263, Japan

Abstract
HIMAC accelerator has been in operation for four years,
without major unscheduled down time. Clinical trial ofcancer radiotherapy, as well as physics and biology
experiments are served well by HIMAC beams.
Operational experience of the accelerator complex isreported from the viewpoint of operations crew and staff in
an application oriented machine. Efforts for highly reliable
and stable beam supply are described on both operation andApproaches to save time andmaintenance aspects.
manpower without reducing the reliability of beam are alsoreported.

expanded its charge to include support to physics
experiment and treatment planning. Several R&D work on
power supplies, beam monitors, radio frequency
acceleration, vacuum system and other relevant fields havebeen carried out under suggestion of and in collaborationwith NIRS researchers. From. FY 96, the preventive semiannual maintenance of HIMAC was also put into AEC's
responsibility. Number of AEC people who worked atHIMAC accelerator operation are nearly 40. This number
includes the above-mentioned activities of AEC from daily
operations to long term maintenance and R&D work for
HIMAC performance improvement.

l.Introduction
Unlike accelerators in physics research, application
oriented machine is required to be operated and maintainedin a fully functional condition without help from a large
Furthermore,physicists.
of accelerator
numberadministrative regulation on manpower directs new way ofrunning a big accelerator complex. Since the machine wasbuilt by four independent manufacturers, no single firm ofeach sub system ofHIMAC can really operate the system asa whole.
AEC was founded by a joint effort of companies
including Mitsubishi Electric Corp., Toshiba Corp., HitachiLtd., and Sumitomo Heavy Industries Ltd., in November
1992. It then started to function as a company to provide
onsite operation and maintenance service of the HIMAC
facility, as well as support for R&D work relevant toHIMAC accelerator. The chronological record of theHIMAC commissioning and operations shows AEC'scommitment. In January 1993, AEC began to operate ion
sources and Iinacs, which accelerated the first beam inMarch '93. The installation of main synchrotron ring andtransport lines was completed in summer '93, when themaintenance of HIMAC building plant (power lines, airconditioning, water and other utilities) were assigned toAEC. Figure I shows plan view of B2F where injector andone of the main rings are installed. Then in September, asmanufacturer tuning by parts was completed, AEC wasentrusted to operate and maintain entire HIMAC facility
under supervision of NIRS Accelerator Operations Section.
Beam commissioning commenced then in November andwe obtained the first beam accelerated and extracted fromsynchrotrons in December. Clinical trial started in June
1994, and continuous operation from Monday to Saturday
was introduced since October '94, during this period AEC

Fig. 1 Layout of the HIMAC B2F

2. The operation of the HIMAC
As medically dedicated machine, HIMAC operation is
dictated by therapeutical needs. [ 1] Present common
practice of particle therapy consists of about 10-20 timesirradiation of the target cancer. Each fraction of irradiation
takes typically a few minutes but usually it is carried out
once a day per patient. It means that a treatment is a matterof weeks, if not months, for individual patient. Implicationis that acceleration for a medical treatment must be able todeliver beam stably during the extended period of 6 weeks
per patient. Further, as the number of patients grows up,
one patient will start treatment right after another patient'streatment. Therefore the beam must be available to irradiatepatients, for an extended period of more than a couple ofmonths. The beam schedule is thus to assure beam time fortherapeutic use as long period as possible. At present, weshut down the machine in August and March for semiannual 5-week-long maintenance. Break at the end of
calender year is limited to about one week. It left us about
39 weeks of therapy beam supply, after taking one week of--'455-

The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

re-confirming period for beam characteristics following
each shutdown. To operate the machine as much stable, wedevote every other Monday to work on maintenance.
Weekly operation pattern is shown in Fig. 2. Therapy
beam time is from Tuesday to Friday, 9 a.m. to 7 p.m., daily.
During this time, carbon beam with intensity of 3xl 08
particle per second must be supplied constantly. Since thetherapy utilizes different value of beam energy to conform
various tumor site in patient, we change the energy
according to treatment schedule. In the horizontal beam
290 MeV/u and 400 MeV/u, and 290 MeV/u and 350
MeV/u for vertical one. It is typically during lunch break
for medical staff, and about 30~40 minutes time isnecessary to adjust and confirm the beam. We save theparameters such as power supply current, static deflector
voltage, rf phases, event timing, and so on, in a 'file' and try
to operate the machine simply reloading and setting thefiled value. The system proves itself by reproducing beamthrough the filed parameter operation and residual amountof tuning is made minimal.
During the beam-field
confirmation and treatment run, beam position and intensity
are monitored continuously by a multi-wire chamber at thedownstream of each beam course. Wave form setting for
respiration-gated irradiation is also done by operator forminimizing the time for treatment.

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parameters can be commonly used and reproducible. In
Table 1, energy and intensity values of lower ring operation
are listed.

SiNe

cH2+Energy[MeV/u]
675
100

180
230
290
350
390
400
401.78~600
650
800Fig. 2 Week operation scheduleNight shift is provided for biology and physics
experiment after therapy. Since these experiments needdifferent beam energy and or intensity level. It is necessary
to change energy and other parameters of the beam at thebeginning of the shift. It is also necessary to return tomedical beam in the morning. As for weekends, various ion
species other than carbon are accelerated for physics andbiology experiments. They include Si, Ar, Ne, He, andothers, which are shown in Fig. 3. Tuning for different ion
takes about two hours, mostly at extraction and transport
from ion source to RFQ linac, even after establishing a'file'd parameter at the preceding beam time. As forsynchrotron ring, beam acceleration for Q/A = 1/2,1000(hour)

1500

Fig.3 Accelerated ion (April, 1 to August, 2, 1997)

24 (hour)Experiment5000~•1656

He150

E2l Beam tuning259

P~r~50 Therapy

913C

Ion
He,C,Ne,Si
Ar,(St 13 )He,C,Ne,Si

nc

z~e

He,C,Ne,Si
He,C,Ne,Si,(Ar)Hz+
He,C,Ne,Si
He,C,Ne,Si
H/
C,Ne,Si,(Ar)C,Ne,Si
Ar+I?
C,Ne,Si
Ar+I?
C,Ne,Si
Ne,Si
Ar
Si

Ring DCCT[pps]He l.OE+lO
Ar 2.6E+7c l.OE+91.9E+98.5E+8No data
c 1.1E+92.0E+10c 2.0E+9He 8.0E+9.
1.4E+l0c 2.0E+9c 9.3E+81.4E+8c 2.0E+91.4E+81.5E+9cNe 8.5E+8
1.4E+84.5E+8HEBT[QQ_s]
2.3E+6
6.7E+86.7E+81.4E+10
1.5E+86.0E+9H 1.3E+10
1.9E+97.5E+9
1.9E+9l.OE+97.7E+8
4.1E+71.8E+8Table 1. Energy and intensity values of extracted beams(Lower ring)
3.Daily Operation and improvements
HIMAC accelerator is now operated by operator crew of3, who are looking at Injector (ion-source and linacs),
Synchrotron (both rings), and Transport (includinginterfacing with treatment/experiment). This number is areduction from initial 7 people crew, and is a result ofintentional effort on making common knowledge and skillof operation and maintenance. However, additional support
is required for operation of other-than-carbon ion, presently.

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The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

Further effort is necessary to proceed more in decreasing
operators.
In an effort to reduce the time necessary for energychange, the effect of "initialization" procedure was checked
and it was found that the magnet at extracted beam transportline needs to be "initialized" to nullify the histeresis effect,
while the effect in the ring magnet is not recognizable.
With this finding, energy change procedure in synchrotron
is modified and beam alignment at the connection from thering to high energy beam transport line is simplified,gammg typically 5~ 10 minutes in the process.
Development of automatic tuning for the transport line isunder progress and will aid tuning operation ofunexperienced operator.
It is also important to meet the request from experimentuser on beam shape, intensity and stability, etc., as much as
possible. Request for a small beam spot can be met byadjusting HEBT Quadruple magnet strength. Request for
more beams at high energy is not always fulfilled. One of
the reasons is a lack of tuning time because we cannot
accelerate carbon ion more than 430MeV/u due to radiation
safety regulation. We set aside every other Monday forbeam acceleration tuning of those new ion/energy, but it
was not enough to obtain the best tuned and reproducible
parameters.
Another problem is to stabilize the beam at 10 2~ 103ppp
level, which is very sensitive to beam path at beamattenuating point, and condition of stabilization often differsfrom the previous one. We need more careful study on
beam transport and acceleration in this problem.
4. Trouble and Maintenance
Various kinds of trouble were experienced during thelast three years. Major troubles that delayed beam supply
for more than one-hour occurred about two-three times ayear. In '95, a magnet-coil bum out due to improper
regulation of coil water circuit, water leak from RF highpower amplifier system water-cooling. In '96, water loss
because of over-fastened and broken packing in the motherline of cooling water system, DTL RF high power trouble
due to power tube and/or high-power amplifier failure. In'97, power tube filament broke. So far, there were only twodays when machine trouble caused cancel or postponementof entire day of treatment. We need to keep and improvethe down time rate as low as possible. In this line,
preventive maintenance work is very important. As can beseen from the above incidences, water leak or loss is one of
the major sources of trouble. Checking and adjusting waterflow at each device is among the menu of Bi-weekly
maintenance, as well as repair/calibration of individual flow
meter.
Maintenance work has been carried out by subsystem(Injector, Synchrotron, Transport) or "group" basis becauseof different starting point in manufacturing andcommissioning. However, since the component technology
is common, we pursue re-grouping of the work in terms offield, such as, power supply, beam monitor, vacuum system,
control computer etc. Also, development work is organizedsuch that members from all subsystem group is engaged tonew i 8 GHz ion source development. Table 2 shows thetechnical items of HIMAC and number of assigned
engineers from AEC.
Technical items
PIG
Ion
SourceECR(l0&18GHz)
Injector
RFSystem
Synchrotron
Vacuum system
Magnets and power supply
Beam monitors
Control systems incl. timing and interlocks
Computers and network system
High voltage devices
Cooling system

Number ofengineers
23+3234445422

Table 2. HIMAC operations activity in technical items
5. Outlook
In order to combine and reduce the load of operator,
more utilization of supervisor system is now discussed
together with an introduction of so-called Time-Sharing
Acceleration. Important pre-requisite is that system can beoperated in the same operation sequence and operators arecapable of at least daily operation of entire system.
Another aspect to reduce load of the operator is totransfer some of the manipulation to user-experimenter: For
example open/close of beam shutter and mesh attenuator in
the injection beam line can be done by user. (Interlocksystem must be maintained as before.)
6. Acknowledgement
We would like to thank researchers at the Accelerator
Physics and Engineering Division ofNIRS headed by Dr. K.
Kawachi for great warmhearted guidance of HIMAC
operation.
7. Reference[1.] E.Takada et al. "Present Status of NIRS-HIMAC", inthese proceedings.

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