JAERI-Conf 95-021

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PRESENT STATUS OF THE :MEDICAL ACCELERATOR HIMAC
S. Yamada, N. Araki, M. Hosaka, A Itano, M. Kanazawa, A Kitagawa, T. Kohno**, M. Kumada,T. Murakami, M. Muramatsu, K. Noda, H. Ogawa, K. Sato***, S. Sato, Y. Sato, E. Takada, A Tanaka,
K. Tashiro, M. Torikoshi, J. Yoshizawa, T. Aoki*, T. Fukushima*, Y. Ishikawa*, T. Kimura*,
R. Oishi*, K. Okumura*, Y. Sano*, Y. Sato*, T. Togashi* and K. Ueda*
Research Center of Charged Particle Therapy, National Institute of Radiological Sciences,4-9-1 Anagawa, Inage-ku, Chiba 263
vertical and horizontal beam lines. The other twotreatment rooms are equipped with a vertical and ahorizontal beam lines, respectively.

Abstract
Clinical study of cancer treatment has been going
June 21, 1994 with HIMAC at NIRS. Moresinceonthan 50 patients have been treated with high energy
carbon beams until August 4, 1995. The preliminary
results look excellent as expected: very light damage onskin surface and remarkable effects on cancer cells.
HIMAC is operated day and night from 7 p.m. on
Monday till 7 p.m. on Saturday for the clinicaltreatment and for basic experiments. About 1,500 hr.
per year are used by clinical trials and 2,500 hr. is open
for physical and biomedical users including researchers
outside NIRS.

2. Commissioning
The HIMAC project was approved in 1987 as
one of the major project of "Comprehensive 10 year
Strategy for Cancer Control" promoted by Japanese
government since 1984. The ftrst beam from theinjector was obtained in late March 1993 with singly
charged He ions. For the dual synchrotron rings, beamtests were begun in November 1993 with doubly
charged He ions. The ions were accelerated to 230
MeV/u with a repetition rate of 1/2 Hz for each ring.
Tests of the slow extraction from both rings weresuccessfully completed in December and the extracted
beams were transported to three treatment rooms withina few days. The length of the extracted beam spill wastypically 300 ms.
After careful tuning of the accelerator system,
biomedical and physical experiments were performed
for a few months. Final check of the reliability of thetotal system was done with the carbon beam irradiation
on a monkey. Clinical trials of the heavy ion cancer
therapy started on June 21, 1994 with 290 MeV/u
carbon ions. The ftrst series of the treatment was
successfully completed for three patients in August
1994. It takes about 90 seconds for a single fractional
treatment, while the precise patient-posttiomng
procedure requires about 20 min. Three treatments per
week and total of 18 treatments for each patient wereadopted as a protocol of the clinical trial.
The interim diagnosis shows excellent results:
radiation damage on the mucous membrane seems very
light in spite of the perfect damage of tumors. All of theftrst three patients got good recovery and already out ofhospital. For some other patients, however, noremarkable improvements were observed.
In the second and the third series of the clinical
trials, heavy ion treatment was applied to cancers at thehead or neck, the lungs, the central nerve system, theuterus, the liver, the prostate etc. More than 50 patientsare already treated with 290, 350 and 400 MeV/u

1. Introduction
Clinical trials and biomedical experiments at
LBL[l] strongly suggest that the heavy ion therapy isvery powerful especially in treating deeply seatedtumors. The advantage of the therapy comes from thewell known characteristics of heavy ions: a very good
three dimensional dose localization in a human body. In
a longitudinal dose distribution, a very sharp Bragg
peak is observed around the end point of heavy ions. A
high value of LET at the Bragg peak is also attractivein the treatment of radio-resistive tumors. Based on thelong experience of radiotherapy with protons and fastneutrons, NIRS adopted heavy ion therapy because of
these excellent characteristics of heavy ions.
The maximum energy of HIMAC is designed tobe 800 MeV/u for light ions with q!A = 112 so thatsilicon ions reach 30 em deep in water[2],[3]. Two ring
structure of the main accelerator of HIMAC will allow
further development of the beam quality andperformance. Ion species ranging from He to Ar arerequired for the clinical treatment. In the facility, there
are three treatment rooms one of which has both*Accelerator Engineering Corporation, 2-10-14, Konakadai,Inage-ku, Chiba 263.
**Present Address: Department of Energy Science, Tokyo
Institute of Technology, 4259 Nagatsuda, Yokohama 226.
***Present Address: Research Center for Nuclear Physics,
Osaka University, 10-1 Mihogaoka, lbaraki, Osaka 567.

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JAERI-Confcarbon ions. Total of 100 patients will be finished by
the end of the fiscal year 1995.

95-021the same path of the hysteresis loop, the magnetic fields
well reproduces the previous values with only setting
the magnet currents.

3. Operation of HIMAC
4. Beam Performance

In the early stage of the accelerator operation, alldevices were turned off over night except for thevacuum system and the control system. After turning onin the morning, it took only 4 hr. to get the accelerated
beam in a treatment room. Most part of the time are
spent in tuning of the ion source and LEBT elements.
After October 1994, HIMAC is operated day and nightfrom Monday 7 p.m. to Saturday 7 p.m. In the day timeof every Monday, weekly maintenance is scheduled.
Accelerator Engineering Corporation (AEC) isresponsible for the machine operation and the weekly
maintenance. Major activities of the accelerator groupof NIRS are set toward the improvements of the beamperformance.
The machine time from 9 a.m. to 7 p.m. of theweekday is scheduled for the clinical trials and from 7
p.m. to the next 7 a.m. is open for users with carbon
ions. From Friday 7 p.m. to Saturday 8 p.m., various
kind of ion species are accelerated for users in physics
and other fields of researches.
An energy change of the synchrotron is required
once in a daytime to select the optimum residual range
for different patients. After changing the beam energy,
the dose uniformity in the irradiation field is checked.
Before and after the daily treatment, energy and beamcourse is changed for the basic experiments.
Total of 37 weeks per year are available asmachine time, other 2 weeks are for beam tuning and13 weeks are scheduled shut down for machine
maintenance etc. About 1,500 hr. per year was spent by
the clinical trials and about 2,500 hr. of machine time
is assigned to the basic experiments and beam tuning.
All devices of HIMAC are controllable through adigital computer system. Optimized set of the operation
parameters are saved in a specified file and usable in
the next operation. With a well established operationfile, it takes only 20 or 30 min. to tune a pair of thesynchrotron rings. It requires nearly the same tinie to
fix the HEBT parameters including the tuning time forthe beam switching. The injector, however, needs morethan one hour, because it takes about 30 min. for an ion
source to get stable.
The reproducibility of the beam performance isexcellent without manual tuning of the magnetic fields.
In order to minimize the field variation due to ahysteresis loop, an initializing technique is introduced
before setting the magnet currents. During theinitializing process, all magnets are excited with themaximum currents of the power supplies. By following

We have two types of ion sources: a PIG and an
ECR sources installed independently on high voltage
decks of 60 kV max. The output beam intensities andemittance of both sources are satisfactory ·for thetreatments[4],[5]. The beam transmission efficiencies
through the low energy transport line and the RFQ are
attained to be around 80% and 90%, respectively, indaily operation. An example of the output beam signalof the injector is given in Fig. I together with rf pulses
for RFQ and DTL.
The two synchrotron rings are operated
independently from each other except that the magnets
must be excited 180° out of phase. The dipole fieldchanges from 0.11 T at injection energy to 1.5 T at
maximum with a ramping rate of 2 Tis (max). The
betatron tunes are chosen typically at 3.68 and 3.13 forhorizontal and vertical directions, respectively. A
typical operation pattern of the ring magnets is 200 msfor a flat base, 700 ms for rise and falling time and 400
ms for a flat top. In Fig. 2, an example of oscilloscope
signals is given for a bending magnet excitation pattern(top), a bump magnet for beam extraction (2nd), beam
signal in the synchrotron ring (3rd) and the extracted
beam signal (bottom). In the signal of the extracted
beam, very big intensity fluctuation can be observed.
This fluctuation is due mainly to a current ripple of thesynchrotron magnets, because no feedback system isapplied to stabilize the extracted beam intensity.
High frequency components of the beam ripple aresuppressed appreciably after careful tuning of thesynchrotron magnet power supplies. At the flat top,voltage ripples of the power supplies of QF and bending
magnets are kept extremely low values of less than
1x10-6 and 1x10-5 , respectively (50 Hz). A beam ripple,
however, remains at high level. By reducing thesextupole
fieldsforchromaticity
correction,satisfactory beam spill is obtained as shown in Fig. 3.
This fact means that the fluctuation of the bending field
may affects strongly on the beam ripple through thesextupole fields.
The whole control system works very well andeven a very low intensity beam of a few hundred
particles per second can be stably accelerated withoutA¢ and Ar feedback loops.
In order to get a high efficiency of the treatment
room usage, it is required to switch the accelerated
beam from one treatment room to the other room in avery short time. The beam switching must be done
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JAERI-Conf 95-021

without introducing the beam into the treatment room.
The reproducibility of the beam position should bebetter than ±2.5 mm at the isocenter. Such precise
beam positioning is realized with a special sequence inthe switching magnet excitation. The new technique forbeam switching takes only 5 min. and will be adopted
in the actual treatment in near future.

(1994).
[6] K. Noda et. al., EPAC94, to be published.

5. Future Developments

HIMAC facility is open for many researchers
who are interested in the heavy ion science as well as
heavy ion therapy. In many researches, HIMAC isrequired to accelerate heavier ions with a variety ofenergies and with high quality. In order to meet thesedemands, third ion source of 18 GHz ECR source isnow under development. Ions from these three ionsources will be accelerated simultaneously with socalled time sharing acceleration scheme and delivered
to a medium energy experimental room, the upper
syncQr'otron ring and the lower synchrotron ring.
A secondary beam will be available within a few
years to investigate the possibility of precise check of
the ion stopping position in a human body. The positron
emitters, such as nc, are considered to be effective forthis purpose. The beam course will be open for otherscientific fields.
Further sophisticated irradiation schemes, suchas a spot scanning method or a three dimensional
irradiation method, are also important in improving theeffectiveness of the heavy ion therapy. An irradiation
treatment synchronized with human breathing is our
first target to reduce the unwanted dose to the normal
cells around the tumor. The treatment will be realizedwith a quick response of the rf-knockout beam
extraction from the synchrotron ring[6].

Fig.1: An example ofbeam signals of the injector.

Fig.2: A typical example of beam signals m thesynchrotron. See text for more details.

6. Acknowledgments
The authors express their sincere gratitude to Drs.
Y. Hirao and K. Kawachi for their continuous
encouragement and fruitful discussions. They are also
grateful to other members of AEC for their skillfu1
assistance.
7. References[1] Castro et. al., Int. J. Rad. Oncol. Bio. & Phys., 29,647 (1994).
[2] K. Sato et al., Nucl. Phys. A588, 229 (1995)[3] S. Yamada, Proc. 1995 PAC, USA, to be published.
[4] Y. Sato et. al., Rev. Sci. lustrum., 63 (4), 2904
(1992).
[5] A. Kitagawa et. al., Rev. Sci. lustrum., 65 (4), 1087

Fig.3.: An example of the beam spill from thesynchrotron. See text for explanation.

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