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

Secondary-Beam Tuning System at HIMAC
Mitsuru SUDA, Yoshihiro ISHI**, Yukio ISHIKAWA*, MitsutakaKANAZAWA, Atsushi KITAGAWA,Mitsuhiro KOKUBO**, Shigeru KOUDA, Takeshi MURAKAMI, Teiji NISHIO, Koji NODA, Eiichi TAKADA,Masami TORIKOSHI, and Satoru YAMADA
National Institute of Radiological Sciences
4-9-1, Anagawa, Inage-ku, Chiba, 263, JAPAN*Accelatetor Engineering Corporation
2-13-1, Konakadai, Inage-ku, Chiba, 263, JAPAN**Mitsubishi Electric Corporation
1-1-2, Wadasaki, Hyogo-ku, Kobe, 652, JAPAN

Abstract
A secondary-beam course have been constructed at
The nc beam analyzed with the newly
HIMAC
developed beam course showed satisfying quality; aproduction rate and a purity are 02% and 97%, respectively.
A computer control system was designed so as to realize
automatic beam-tuning; i.e. processes, such as calculationand setting of the device parameters, data acquisition andanalyses for particle identification, and optimization ofdevice parameters, are executed without intervention of
In a preliminary test operation, automaticoperators.
tuning of nc beam was performed within 40 min. The
reproducibility of the beam quality was very well.

pair of bending magnets, eleven quadruple magnets, aTheproduction target and an energy degrader [4].
principle to separate ions with specific mass A and charge Z
is as follows. (1) Fragments are produced in the target atthe focusing point FO. (2) Particles with a given A/Z value
are selected at the dispersive focusing point Fl after the firstbending magnet (BMI). (3) Particles separated at Fl lose
their energy in the energy degrader by an amountdetermined mainly by their Z values and the degrader
thickness. (4) Particles with desired A and Z are focused at
the doubly-achromatic focusing point F2 with the second
bending magnet (BM2).
Particles are identified by a AE counter at F2 and Timeof-Flight (TOF) counters at Fl and F2. The TOF counters
also work as intensity monitors in the beam tuning.

1 Introduction

5?

Clinical trials of cancer treatment by using high-energy
heavy-ion beams have been practiced since June 1994 atHIMAC (Heavy Ion Medical Accelerator in Chiba) [1].
Heavy-ion beams have the following advantages: (1) gooddose localization due to the Bragg-peak, and (2) large
values of relative biological effectiveness. In the cancertreatment, it is important to determine residual ranges ofirradiating ions with high accuracy. At present, the range
is calculated based on the CT values obtained by X-ray CTs[2], and the errors involved are not negligible in some cases.
A more precise method for the range measurement isrequired in order to take full advantage of the heavy-ion
Radioactive isotope beams (RI beams) arebeams.
expected to be an excellent tool for the range measurements.
One can estimate a position where a beam stops with highaccuracy by detecting annihilation gamma rays. Other
application includes confirmation of irradiated targets byemploying the positron emission tomography [3]. Thus, asecondary-beam course to select mainly the positron
emitters has been constructed at HIMAC [4,5]. In thisreport, we describe an outline of the control system andsome preliminary results obtained in the beam tests.

2 Secondary-beam course at HIMAC
High-energy secondary beams can be produced by theA layout of theprojectile-fragmentation method.
secondary-beam course at HIMAC is shown in Fig. 1. The
beam course, named as SB 1, is a spectrometer comprising a10m
2nd Bending
MagnetFl

F2
TOFcounterdelta E counter

TOFcounter
Energy Degrader

1st Bending
Magnet~FO

Primary beams from the synchrotron

Fig. 1 A layout of the secondary-beam course at HIMAC.

3 Tuning system of secondary-beam
3.1 Requirements to the control system.

Beam courses for medical use are required to fulfill thecharacteristics of high reproducibility of beam quality andThe beam quality includes energy,easy operation.
intensity, size, and purity of the secondary beams. The
easy operation is indispensable so that operators without
special knowledge about reaction products can operate thebeam course as a routine work. Furthermore, the tuning
time should be as short as possible to in~rease available
beam time for users. A new control system (SB controlsystem) was designed and constructed, in addition to the-261-

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

existing control system, to satisfy above requirements.
The SB control system was designed to possess thefollowing functions: (1) calculating and setting the device
parameters (magnets, slits, and so on), (2) monitoring thosedevices during the operation, (3) acquiring and analyzing
data concerning with the primary beams and secondary
beams, and (4) automatically adjusting the device parameterto optimum values. The last item, i.e., automatic beamtuning, is strongly desired for the easy operation.
3.2 The SB control system and existing system

The SB control system comprises two computers: SBGCU (Secondary Beam Group Control Unit), and SB-DAU(Secondary Beam Data Acquisition Unit).
Thesecomputers are connected with an existing main computer ofHEBT-SCU (High Energy Beam Transport System ControlUnit) through a network as shown in Fig. 2.
HEBT-SCU is a main part of the existing control system
of High Energy Beam Transport System. Beam transport
devices, such as the magnets, slits, targets, and the degrader,are connected to HEBT-SCU. Thus, HEBT-SCU sets
device parameters after receiving those values from SBGCU, and monitors the device status during the operation.
The SB control system was designed to be independent
from the existing system so that the former can be debugged
and modified without disturbing the latter.
Secondary beam course
control computer .......r------,
Supervisor System Computer

SB-GCU

from the ~E counter is fed to an amplifier and is digitizedby an ADC (mtt DSP 8112). The TOF counter is a plastic
scintillater with a size of 50x 120 mm and a thickness of0.5mm. A couple of photomultiplier tubes is connected at
the both sides of the TOF counter. Mean values of two
signals are adopted as timing signals to avoid the position
dependence. Start and stop signals are fed to a TAC
digitized data together with ~E data are stored in thememory module (mtt DSP 8031) and are transferred to SBGCU through LAN during beam-off intervals. Conversionand storage takes about 20 JlS for each event, and thememory module can store the data up to I 0000 event perspill.
Secondary Beam Group Control Unit

SB-GCU plays the ieading role in the SB control system
except for the acquisition of the PI data. All the data, suchas parameter sets and observed data, are stored in SB-GCU.
Moreover, SB-GCU works as a man-machine interface in adevelopment stage, i.e. analysis formulae and programmedsequences are set or corrected on the console of SB-GCU.
Device parameters calculated by SB-GCU are sent toHEBT-SCU. Information of device status is sent backfrom HEBT-SCU in the opposite direction.
As stated above, three computers exchange a lot of dataand information. In order to avoid congestion of thenetwork, the data transfers are carried out during beam-offintervals. Figure 3 shows timing of the data transfer.
Beam-off triggers initiate the transfer of the device
parameters and the PI data. Change of device parameters ·occurs only in the beam-off intervals.
Beo.M

I Ij..
~I
I Bean of'f'f Triger

SBC - DAU

I Beoon on~ ll"iger

Data

Do-totakeing-tokeing

SB-DAU
Beam gate

PI data

SBC-GCU
Anolys1s or colculotion

HEBT-SCU~

Ano.lysis or calculation

De iceP roMe1:er

Device>Sto.1~.;sPoro.Me1l'r set oncl
status MoniterDevices,
Magnets, target, etc.

Counter,
TOF, DeltaE, etc.

DeviceParaMeterc==Jro.sk
Dl?vice

Status. --f;;o- ~~;~sferFig. 3 Time chart of the data and parameter transfer

Fig. 2 Outline of the SB control system.

4 Procedures of automatic beam..;tuning.

3.3 SB control system
Secondary Beam Data Acquisition Unit

SB-DAU is a front-end processor using the VME bus(Eaglel62LX), and is devoted to data acquisition ofparticle-identification (PI) data. Detectors, TOF counters
and a ~E counter, and modules for PI data are controlled bySB-DAU. The~ counter is a silicon detector with a sizeof 48x48 mm and a thickness of 325!Jlll. Analog signals

Automatic beam-tuning procedure consists of twophases: (1) tuning to the primary beam for calibrating
magnet strength and PI signal, and (2) searching for
optimized set of parameters for secondary beam of interest
as defined by Bp value and an area in A/Z plane.
Optimization is done by maximizing the relative yield ofdefined secondary beam over total yield.

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The following procedures are employed in the automatic
beam-tuning. Firstly, beam-transport parameters for theprimary beam are calculated and the devices are set to thoseThen, (1) the field strengths of BM1 andvalues.
quadrupolJ magnets placed upstream from the F1 are
optimized so as to give the maximum intensity of the TOF
counter at Fl. (2) The field strength ofBM2 is adjusted by
the same way as the case of BMl. Second procedure isimportant to estimate the energy loss through the degrader.
The currents of the quadrupole magnets are changed withthe same ratios as those of the bending magnets during theoptimization procedure. (3) The PI data of the primarybeam particles are analyzed and mapped on an A-Z plane.
Based on those data, an area where the secondary-beamparticles would occupy is estimated.
Secondly, parameters for the secondary beam, arecalculated from the optimized parameters described above.
(4) A production rate and purity of the secondary beam canbe estimated from the PI data, assuming that the events
inside the predetermined area are desired secondary~beamparticles. (5) The devices, such as bending magnets,
quadrupole magnets, and slits, are adjusted to maximize thepurity ofthe secondary-beam particles.
5 Results of the beam test using 12C beams
An example of the particle-identification data is shownin Fig. 4. The primary beam was 12C with energy of 400
MeV/u. A beryllium target with a thickness of about 51mm was used. An aluminum degrader was with a wedge
angle of0.689 deg and a thickness at center of about 7 mm.
The relation between NZ and Z is plotted in the twodimensional spectrum (top) and TOF and dE data aredisplayed (middle and bottom). In order to demonstrate
excellent separation between the adjacent particles, the dataof Fig. 4 were collected in the relatively poor condition fornc production (the degrader was removed). If all thedevices were set in the optimum condition for production ofnc, the production rate and the purity were 0.2% and 97%,respectively. The results were quite satisfactory.
A process of the automatic beam-tuning was also tested
using ihe same ,primary beam and target. The magnetic
rigidity of the bending J;llagnets were searched within arange of ±0.3 % by a step of 0.05 %, and the slits width at
Fl and F2 were adjusted. The currents of the quadrupole
magnets were varied by the· .same ratios as those of thebending magnets. Starting from the calculated parameters,
the system could fmd the condition for production of the nc
beam of the mentioned puricy. and rate in about 40 min. It
was also tried to produce a new secondary beam, 8B.
Using the similar procedures to the nc case, the system
could adjust the devices for production of the 8B beam
successfully in 40 min.

Fig. 4 Particle identification data (top) and TOF and dE data(bottom) in the beam using the 12C beams.
References[1] E. Takada et al., "Present Status of NIRS-HIMAC", inthese proceedings.
[2] M. Endo et al., "HIPLAN -a heavy ion treatment
planning system at HIMAC", J. Jpn. Soc. Ther. Radiol.
Oncol. 8 (1996) 231.
[3] J. R. Alonso et al., IEEE Trans. Nucl. Sci. NS-26 (1).
(1979) 3003.
"[4] M. Hosaka et al.,. "The Optical Design of HIMAC
Secondary Beam Course", Proc. 1Oth Symp. On Accelerator
Sci. and Tech., Hitachinaka (1995) p.410.
[5] S. Kouda et al., ''New Secondary Beam Course for
Medical use in HIMAC", Proc. Particle Accelerator
Conference, Vancouver (1997), to be published.

The performance of the beam course and the control
system so far has been very satisfying. Test operation
employing the beams other than 12C is in progress.

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