The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

COMPACT PROTON AND HEAVY ION SYNCHROTRON FOR
CANCER THERAPY AND BIO-SCIENCE
K. Endo, S. Ninomiya and Z. Fang, KEK, Tsukuba, JapanS. Yamada, NIRS, Chiba, JapanY. lshi, S. Fukumoto, A. Teramoto, M. Takada and I. Uetomi,Mitsubishi Electric Co., Kobe, Japan
G. I. Silvestrov, BINP, Novosibirsk, Russia
the same project, the injection energy of 1 MeV/u isassumed here.

Abstract
Compact proton and heavy ion synchrotrons are being
discussed in order to promote their uses in the fields of themedicine and bio-science with a reasonable invest cost.
Both synchrotrons can share the same components except
for dipole and injector but with an enlarged circumference
for the heavy ion ring. To realize a small accelerator
without using the superconducting magnet that requires aninfrastructure for the cryogenics, the use of the high fieldmagnet is inevitable. Moreover, it also requires the wide
range frequency modulation of the RF system at highacceleration voltage. This study includes the improved
lattice designs for both rings that are envisaged as anactual proof of the compact synchrotron.

1 INTRODUCTION
The carbon ion therapy is now noticed for its
remarkable improvement in the radiotherapy because thehigh LET particle gives a lethal damage to the tumor
tissue almost independent of the cell cycle. It benefits in
reducing the radiation treatment sessions compared tothose of proton [1]. However, proton therapy also serves
as an advanced modality of the medical treatment. Bothaccelerators for proton and carbon ion can share their roles
as a hadron therapy which is recognized to be idealbecause it can localize the depth dose to the tumor volume
affecting little. to the surrounding normal tissues. In
general, the proton machine can be manufactured
relatively cheaper than the heavy ion machine, so theformer may be constructed at the locally distributed clinics
around the medical centers which serve for the research anddevelopment of new therapeutics in addition to thecomplementary role to the local clinical centers.
This kind of accelerator does not belong to the small
accelerators mainly dedicated to the radiotherapy such as
cyclotrons and synchrotrons which are designed withestablished methods, but it depends on the potentialities
existing in the well understood technologies and pursues
their extremity [2, 3, 4].To make the accelerator as small
as possible, it must adopt the high field magnet of 3 T or
higher which is challenging in the compact cyclotron [5].
From these view points, this study deals with thesynchrotron which is expandable from the proton machine
to the heavy ion machine based on the same concept [6].
As the laser-based heavy ion source will be developed in

2 LATTICE DESIGN
The ring circumference is almost determined by thefield strength of the dipole magnet and the acceleration anddeceleration periods are limited by the temperature rise of
its coil. The required power is supplied by the discharge ofthe capacitor bank of about 100 kJ but the excitation
current cannot be controlled during acceleration except forthe peak current [7]. Therefore the gradient of thequadrupole magnet must be controlled precisely bytracking the dipole field or its current. After investigating
several candidates of the lattice suitable to the compact
synchrotron, the ODOFBF lattice for proton and theODOFBFDFBF lattice for heavy ion are found promisingand their parameters are given in Table 1.
T able 1 Lattlce. parameters o f the_j)l"Oton anrmgs.
C 6 + ion
Rin.-&Proton
Max. energy (MeVIu)
200
200
Injection energy (MeVllf)_12
Max. dh>_o1e field l_TI_
3
3
Length of dipole (m)
1.126
1.126
Bending radius (m)0.71651.4331
Number of dipoles
48Max._guad_gradientj_Timl
4242
Length of quad (m)0.10.1
Number of quads
1228
Circumference (m)
11.3
24.2
Superperiod
44Tunes (hor I ver)2.25 I 1.25
2.75 /1.75
Max. beta function _illx. IJti
4.42 I 11.33
4.40 I 14.73
Max. di~ersion l.ml
0.420.85
RF frequency (MHz)
1.7 - 15.0
0.6- 7.0
Harmonic number
11
Max. Ace. Voltage (kV)1326Ace. time (msec)
55
Number of RF cavities
24R~tition l.H~
<10<10Unit cell structure
ODOFBFODOFBFDD
FBF

Focusing quads close to both ends of dipoles are
introduced to increase the tunability as well as to allow-426-

The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

the normal beam entry to dipoles which will relax thedesign of the dipole magnet ends. This choice also
benefits in reducing the dispersion function a great deal byincreasing the horizontal tune to 2.25 for proton and 2.75
for heavy ion. But the drawbacks are the increases of themaximum gradient and the betatron functions for bothfocusing and defocusing quads. As the vertical betatronfunction for the dipole remains small, it does not affect tothe dipole gap height for both rings.
As the saturation of the quad yoke becomes serious at
higher gradient level, it is desirable to increase the core
length for the better tracking of the quad to the dipole
field. The estimated saturation at 45 T/m for the present
10 em core length is almost 40%.
Layouts are given in Fig.1 and their twiss parametersin Fig.2 for the proton and carbon ion ring.

p=l.43m

200 MeV proton ring
QD

QF

B

200 MeV/u C(6+) ring
QF

R=3.85m_ _ _ _ _ _ _ ____j__ _R_=I_.s_m_e3 QD
E9----'.QDLattl<e conllguratiooor C(6+) and proton rinp

Figure 1: Magnet configuration for a superperiod of theproton (right halt) and carbon ion ring (left halt).

Figure 3: RF parameters for(a) Proton ring, and (b)Carbon ion ring.

3 BEAM APERTURE ANDSEXTUPOLE COMPENSATION
Several limitations are imposed on the compact ring,that is, the useful beam aperture is within ±3 em or sohorizontally and ±2.5 em or so vertically in the dipole
magnet, the allowable momentum spread under thesynchrotron oscillation is within ±1.5%, and thenormalized emittance at injection is 101t mm•mrad or lesswhich limits the beam intensity and requires higher
machine repetition rate. Therefore, the dispersion function
should be as small as possible to reduce the horizontal
beam excursion by the large momentum shift.
The estimated beam aperture is given in Table 2 under
the above limitations.
Table 2: Half beam aperture requirement (unit: em).
The COD is not included
C 6 + ionProtonRing(hor./ver.) (7t mm mrad)f.
Dipole (hor./ver.)QF (hor./ver.)
QD (hor./ver.)Long SS (hor./ver.)Short SS (hor./ver.)10110
2.7 I 1.3
3.2 I 1.7
2.0 I 4.2
3.2 I 4.1
3.1 I 1.4

10 I 5
4.2 I 1.4
4.4 I 1.6
2.1 I 4.0
4.3 I 3.9
4.3 I 1.6.o............~........._..L_,_,~~...JQF

BQF
1.2

1.6s(m)

2

2.4

Oll3

2.8s(m)Figure 2: Twiss parameters for a superperiod of (a) proton(ODOFBF) and (b) carbon ion (ODOFBFDFBF) ring.
BX and BY are the horizontal and vertical beta-function,
respectively, and EX the horizontal dispersion function.
Lattice structures are also shown at the bottom of eachfigure.
The fundamental RF parameters are given in Table 1.
By choosing larger horizontal tune, the transition energy
increases and the momentum excursion due to thesynchrotron oscillation decreases. Other parameters areshown in Fig.3 for both rings. Acceleration of particle ina short time in a small ring requires the high RF voltage
and wide frequency range [8].

Most deteriorating field is the sextupole component in
the dipole. The method of its compensation will be doneby adding compensation windings to each dipole and/or
independent sextupole magnets at straight sections. Bothrequire the current control which tracks the dipole field.
The beautiful compensation results from controlling theflux passage in the iron pole and yoke by the current of
the embedded correction windings in the upper and lower
magnetic poles. The flux distribution in the beam apertureis affected by the locations of the windings which should
be determined by the numerical field calculations. The
resultant field distributions by the static 2D calculation
are given at the injection and maximum fields in Fig.4.
The optimum winding position should be determined
carefully by the 3D calculations.

-427-The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001___ ;_____ :___""';"'_~ __!___ _(~ FieiJ distributiok
i atinJectio~

E.

i:9'~o.,..

;

..

;

-uo·:---- E:

3.1

t:
':
=---T·--r·--:---C!l·--'It\io B(6.0k-800) (f) -y-:---o B(6.6k-800) (f) q,"JlX B(6.6k-900) (f)\ i'----:.----~-----~--~-.:---i(b) P.ield distribu.1:io~~ peak! curre*t j ;i!

! :i-··r·---1·--··r···r··-0y(em)-w.

-(a)Prbtonriag------~--------------i---~---------_._:
Sejuupole in di~e = 2.5 TJmA2iassumed.
Se:x:tupole is not ¢0rrected:

Colle(lti.on windings•..

···· ·t?:···<>·· B(S.~k-soO) (fl.

.' ''''! ----r-----------·:--·(c) Coil con&gulationof dipole magnet

2.9

0 B(O)(T)!:
0 B(6000)(T) L<---0 B(l2000) (f) . •X B(l8000) (T)· +··· B(24000)(T) ..

1..
0x(cm)x(mm)Figure 4: Improved field distribution with thecompensation windings embedded in the magnet yoke at(a) the injection field and (b) the peak field (figures are thecurrent in AT). (c) Cross-section of a quarter of the dipole.
The auxiliary windings require the bipolar operation tocompensate from the injection field to the maximum field
against the induced voltage due to the main coiL
Sextupole magnets is powerful to compensate the error
sextupole field in addition to the chromaticity controL
Their effects on the beam stability is simulated using
the beam tracing code assuming either that the sextupole
component distributed over the entire dipole or that itexists at the middle of the dipole as a thin lens. As bothcases gives the similar effect to the beam, only the latter
cases are shown in Fig.5.
In simulations for the proton ring, beams with different
momentum between -1.5 and 1.5% were traced for 2000
revolutions under the influence of the RF field assuming
the sextupole component of 2.5 T/m2 in the dipole fortwo cases with and without correction by 4 sextupole
magnets symmetrically placed at 4 straight sections. If the
sextupole field is not corrected, the betatron amplitude of
proton with large momentum deviation grows beyond theaperture allowed for the present ring.
The beam aperture dependence on the sextupole fieldstrength of the dipole is estimated for the same horizontal
and vertical emittances. The synchrotron oscillation of
proton with dp/p=±1.5% is assumed within stability limit
considering the proton survival at injection for theimposed horizontal aperture of x=±3 em. The dynamic
aperture is defined here as the emittance at the beginningof the beam tracing if the proton survives after 5000
revolutions. Two cases are given in Fig.6 for tunes (QX,QY) = (2.25, 1.25) and (2.25, 0.75) for the same proton
ring. Wider dynamic aperture is expected to the larger
vertical tune.
Authors are indebted to Professor Y. Hirao of NIRS andM. Seya of NISTEP who have paid a great effort tomaterialize this project.

Figure 5: Effect of the sextupole component of thedipole (2.5 T/m2) on the proton behavior in the horizontal
phase space at injection. Sextupole component is (a) notcorrected and (b) corrected. The effect of the synchrotron
oscillation was considered.

Sextupole strength k2 (m'3 )Figure 6: Dynamic aperture dependence on thesextupole field strength for dp/p=1.5% proton under theinfluence of the synchrotron oscillation. k2=0.5B"/Bp(Bp=0.20 T•m at injection and 2.15 T•m at 200 MeV).

REFERENCES[1] Y. Hirao, "Results from HIMAC and Other Therapy
Facilities in Japan," CYCLOTRONS 2001.
[2] 1.1. Averbukh et al, "Project of Small-Dimensional
200 MeV Proton Synchrotron," EPAC88, pp.413-6.
[3] L. Picardi et al, "Preliminary Design of aTechnologically Advanced and Compact Synchrotron
for Proton Therapy," Internal Report RT/INN/94/20,
1994. L. Picardi et al, "Preliminary Design of a Very
Compact Protosynchrotron," EPAC94, pp.2607-9.
[4] K. Endo et al, "Table-Top Proton Synchrotron Ringfor Medical Applications," EPAC2000, pp.2515-7.
[5] J. Kim, "Design Study of a Superconducting
Cyclotron for Heavy Ion Therapy," CYCLOTRONS.
[6] 1.1. Averboukh et al, "Compact Carbon-Ion
Synchrotron for Cancer Therapy," APAC'Ol, to bepuiblished.
[7] K. Endo et al, "Resonant Pulse Power Supply for
Compact Proton and/or Heavy Ion Synchrotron,"
APAC'Ol, to be published.
[8] S. Ninomiya et al, "Non-Resonant RF AcceleratingSystem," EPAC2000, pp.1981-3.

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