JAERI-Conf 95-021

3a4-5
BEAM-QUALITY MEASUREMENTS ON HEAVY ION THERAPEUTIC BEAM OF HIMAC
Naruhiro MATSUFUJI, Tatsuaki KANAI, Hiromi TOMURA, Yasuyuki FUTAMI,Akifumi FUKUMURA*, Toshiyuki KOHNO** and Kiyomitsu KAWACID
Division of Accelerator Physics and Engineering, *Division of Radiation Research,
National Institute of Radiological Sciences, Chiba, Chiba, Japan**Department of Energy Sciences, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
Abstract
Fluence spectra of fragment particles
caused by spallation reactions between heavy(polymethyland PMMAbeamsionwithmeasuredweretargetLucite)methacrylate;eachformethodtelescope~E-E counterfragmented element. Measurements were carriedout for carbon beams of 290 MeV/nucleon and400 MeV/nucleon at Heavy Ion Medical
Accelerator in Chiba (HIMAC), and 135
MeVlnucleon carbon beam at RlKEN Ring
Cyclotron with changing the thickness of target
material. Incident beam was broadened with apair of wobbler magnets and a scatterer, in thesame way of clinical trials which have been
carrying out at HIMAC. Results were comparedwith the calculational expectations.
1. Introduction
In tumor therapy using heavy ion beams,
it has been well known that incident heavy ion
particles cause spallation reactions with theelements which compose the body. Hence,various kinds of particles were produced and hit
the target. It is of importance to measure theirfluence spectra for each fragmented element toestimate their influence on tumor therapy, and to
brash up our treatment planning as well.

monitor position. A stack of the plates of
PMMA was selected as target material as it has
similar composition with muscles. At theirradiation site, the detectors for the particleidentification were placed. The detectors had
comparatively smaller front surface to avoid
entering plural fragment particles. In the setup atRIKEN, a coincidence detector, made ofannular NE102A plastic scintillator, of 5.0 mm
in diameter was positioned to distinguish an
event by one fragment particle from those bynoises. A proportional counter with tissueequivalent gas was used to estimate the amountof energy transferred to biological system. A
totally depleted silicon surface barrier detectorof 11.3 mm in diameter and 1.0 mm inthickness was used as a ~E counter to measure
the energy loss ~E in the detector and to makeenergy calibration. At the end of the beam line,a BGO scintillator was utilized as an E counterto measure the residual energy E of incident
particle. The scintillator had a cylindrical form,
15.0 mm in diameter and 15.0 mm in length.
The measurements were carried out for carbon
135 MeV/nucleon beamatE5 port.

2. Experimental Setup
Figure 1 shows schematic diagrams ofdetector systems for measurements at RIKEN
and HIMAC. According to Bethe formula,fragment particle can be identified with theparameter A7! by measuring its total energy E
and energy loss ~E. The systems were basedon the counter-telescope method [1]. Incident
beam was sufficiently uniformed to 10.0 em indiameter with the flatness of 95% at the isocenter by a pair of wobbler magnets and ascatterer[2]. A beam monitor, made of NE102A
plastic scintillator of 1.5 em in thickness, had
front surface of 20.0 em by 20.0 em to countthe total number of incident particles. The beam
diameter was less than 5 em at this beam

Fig.1 The schematic diagram of the detector
system.
In the setup at HIMAC, a NE1 02A
plastic scintillator of 40.0 mm by 40.0 mm and5. 0 mm in thickness was used as a ~E detector
instead of Si semiconductor detector. Energy-451-

JAERI-Confresolution of plastic scintillator is generally
inferior to semiconductor detector, however,scintillator has very superior characteristic onparticle identification regarding that the response
function of scintillator tends to enhance thedifference of P:Z} on lighter elements such ashydrogen or helium which are important to bewell identified on this work, whereas the outputof Si semiconductor detector is strictly
proportional to AZ}. In this setup, Sisemiconductor detector was used for energy
calibration. A larger BGO scintillator ofrectangular form of 40.0 mm by 40.0 mm by
300.0 mm was used as an E detector.
Measurements were carried out for carbon 290
and 400 MeV!nucleon beams at the bio port,
therapy port BHC and CHC of the HIMAC.
3. Analysis
Figure 2 illustrates an example ofparticle identification by E-AE scatter plot
obtained from incidence of carbon 290
MeVInucleon beam to the target material of
120.7 mm in thickness. The abscissa represents
the residual energy E measured by the BGO
scintillator and the ordinate denotes the energy

95-021energy deposition of each fragmented element
was derived by picking up upper and lower
channels of the distribution spectra on Si
semiconductor detector. Here, the channel of Si
semiconductor detector was calibrated bycorresponding a peak channel of the groupregarded as primary carbon with its amount ofenergy deposition calculated for each thicknessof target material. As for calculational
expectation of the energy deposition, maximum
and minimum values were given by thefragment produced just before the detector andthe fragment produced at an entrance of target
material, respectively.
The result was summarized in Fig. 3 forthe incidence of 290 MeV/nucleon carbon beamin PMMA of 112.1 mm in thickness. The
experimental and calculational range ofdeposited energy was well overlapped for eachother on each fragmented element. Therefore,. it
can be said that fragment particles were clearly
identified from carbon to hydrogen with thedifference of Z and A by regarding the highest
group as primary carbon in E-AE scatter plot.
70>

60:::!:

50CD>.

~CDc40'C

30UJ~(/)

0c.
Cl)

200

100

Atomic Number of Fragment

Residual Energy E (BGO)

Fig. 2 ·The scatter plot of the residual energy E
and the energy loss AE for 290 MeV/nucleon
carbon beam in PMMA 120.7 mm in thickness.

Fig. 3 Experimental and calculational energy
deposition on Si semiconductor detector for
290 MeV/nucleon carbon beam in PMMA of112.1 mm in thickness.

loss AE from the plastic scintillator. Fragment
particles were clearly separated to some groups.
To identify each group in the AE-E
scatter plot, the amount of energy deposited in
the Si semiconductor detector was comparedwith the calculational expectation for eachfragmented element which was regarded on AEE scatter plot as filled in Fig.2. Experimental

Fluence spectra of each element were
derived from the number of particles in eachgroup by normalizing with the total number ofincident particles because of the flatness and thebroadness of the incident beam. Figure 4 to 6
displays the fluence spectra at the incidence of135, 290 and 400 MeV!nucleon carbon beam
respectively. In these figures, dots represents
the results of this work and lines are-452-JAERI-Conf 95-021

PMtwM
0.6

"TIcCD
0.2 5:!'o~...Cll>-

E·.:::-0.9

ji;

0.1-..
CD0zo,jii:

0.6cG)

0.4
0.2

0.1

:::IImcc

3-CD:::IIzo.z
000

Thickness of PMMA (mm)

0(J)

0.2

LL

0.5-...
'T1

0.3G)
()

Ill

0.6

CD

0.4

Q.

ca3:sQ)()cQ):sE·;:"TICD:::IInC'CI

0.15-0.70.5>-0Q.

0--...

CD

0.8!!
czoz

Thickness of PMMA (mm)Fig.4 Fluence Spectra of fragments for 135
MeV/nucleon carbon beam.

Fig.6 Fluence Spectra of fragments for 400
MeV/nucleon carbon beam.
4.Conclusion!!
c--...

0.8

E

0.6

foz

CD:sn

CD

-...
-->Cll·.:::

-0'T1

Q.

0Reference smca

[1] F. S. Gelding and B. G. Harvey, Ann. Rev.
Nucl. Sci. 25 (1975) 167[2] T. R. Renner and W. T. Chu, Med. Phys.
14 (1987) 825[3] L. Sihver et al., Proc. of NIRS Inti. Sem.
on the Appl. of Heavy Ion Accel. to Rad.
Therapy of Cancer in connection with XXIPTCOG Meeting, to be published.

30.4

CD:sG)()cG):s

Fragment particles included in thetherapeutic beam were well identified with the.6.E-E scatter plot by a thin plastic scintillator
and a BGO scintillator. The fluence spectra
were obtained for each fragmented element andagreed well with the calculational expectations.

Ill0.2zo.z

LL0Thickness of PMMA (mm)Fig.5 Fluence Spectra of fragments for 290
MeV/nucleon carbon beam.
calculational results by Sihver et al. [3] for thesake of comparison. The experimental data
show good agreement with calculational ones.

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