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

Beam Commissioning of Synchrotron Ring at Hyogo Ion Beam Medical CenterY. lshi, A. Itano*, Y. Yamamoto, H. Inoue, Y. Kijima, J. Matsui, S. Fukushima**,
A. Fujita**, H. Morita**, T. Kagawa**, K. Nishikigori***, H. Isa***, Y. Honda***Mitsubishi Electric Corporation, Kobe, Japan*Hyogo Ion Beam Medical Center, Hyogo, Japan**Mitsubishi Plant Engineering Corporation, Kobe, Japan***Accelerator Engineering Corporation, Chiba, JapanAbstract
Beam commissioning of the synchrotron at Hyogo Ion
Beam Medical Center started on March 2000. The requirements for the beam has been successfully attained. Regular
operation for clinical trial has been carried out since May2001.

1 INTRODUC TION
The synchrotron at Byogo Ion Beam Medical Center[!]
was designed to provide proton, helium and carbon beams
whose required intensity is 5Gy/min at the end of thehigh energy beam transport line. The injection energy is5MeV/u for all the beam species. The extraction energy
range are 70- 230MeV/u for proton and helium, and 70320MeV/u for carbon. Corresponding range of magneticrigidity is 0.3235 - 5.576Tm. A third integer resonance isused for the slow beam extraction. The ring has 6-fold symmetry(Figure 1); each superperiod consists of two regular
FODO cells(Figure 2). Operating tunes are (3.69, 3.14)
at the injection and (3.67,3.12) at the extraction as shownin Figure 3. The main parameters of the synchrotron areshown in Table 1

010

Path Length(m)Figure 2: Lattice Functions.

Extraction energy
Beam intensity

Extraction

BM: Dipole
QF: Focusing Quadrupole
QD: Defocusing Quadrupole
SXF,SXD: Sextupole for
Chromaticity Correction
ESD: Electrostatic Deflector
SM: Septum Magnet
ESI: Electrostatic Inflector
RFC: RF Cavity

Repetition rate
CircuJpference
Symmetry
Structure
Number of cells
Operating point
Harmonic number
RF frequency
RFVoltage
Number of bending magnets
Number of quadrupole magnets
Bending field

70-230 MeV/u {p, He)
70-320 MeV/u (C)7.2e10pps (p)1.8e10pps (He)
1.2e9pps (C)0.25- 1Hz
· 93.6m
6-foldFODO
12(3.69,3.14) injection(3.67,3.12) extraction ·30.993-6.417 MHz
5.2kV(3kV operation)
12 ( +1 for monitor)
24
0.076T ~ 1.324T

Table 1: The main parameters of the synchrotron.

Figure 1: Layout of the Synchrotron.

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

3.5 "'"I"""~----.-----.--,~,___...,,....,,,-I-.---.;.7"71III,- .... ._,._

I--"'':',-.-\

I,'

shown in Figure 4. Nominally 200p.s pulse is injected. The
injection efficiency is calculated as 35%.

//\- -\\\._, ,:/~..._._._._-----'--\\ - - - - : ,,··-~-~-- I~ -'-\,/ ->~II\3.3', -:r-....

3.4
I I\I'~ ~\IIII.... ,_- ' f'II_) .- ....-/I

1',".-\'_,_.. . . . ,:-'-- -\- -.~-'- ~- -_-. . -.,,:'~::: =- ~.7- ~---~..... :...

I\- ---~f--_-3.2

I-\', \,'I
I\'//1 I,"\I,-(._injection,·.....

I'/-.t._,, .• ) . l
3.1

•I'

I.·:- ... • •,' ~/\--~.exl(actiq_n/1\//I/,._ ._I' II' I·\,',\I,I-- --. -. - . ",\....

I•/,\

3~-~-~~-~~----~--~~~~

3.5

3.8

3.7

3.6

3.9

4

Figure 3: Operating Point.

2
2.1

Figure 4: Injection beam and pulse of the bump magnets.

BEAM COMMISSIONING

Excitation pattern of magnets

Prior to practical beam commissioning, excitation patternsof pulse magnets had been made using data from magnetic
field measurements. We assumed that the field as a function of the excitation current can be fitted to the polynomial functions. Fifth order polynomials are used for maindipoles, main quadrupole and sextupoles. These functions
realize good agreement even in low and high field region
where remanent and saturation effects are signifiacat respectively. Other magnets i.e. bumpers, steerers and correction quadrupoles are fitted to 2nd order polynomials.
Field measurements were done by using long coil. Thus,in the case of main dipole, we obtained Bl as a function ofI represented as
5Bl(I) =L aJi.

(1)

i=O

All the patterns are produced on a computer as datapoints. A pattern has data points corresponding frequencyof 1440 Hz. Data sets are sent to the man-machineinterface(MMI), then it is modified if necessary by an operator and sent to VME controller which is connected to eachmagnet power supply[2].
During ramping of the magnets, RF frequency of theaccelerating cavity is varied by a B clock counter. One
count of the B clock corresponds to 0.2 gauss in the bending field measured by using a reference bending magnet in
the power supply room.

2.2

Beam InjectionWe started beam commissioning from helium beam. The
first turn beam injection was observed by using faraday cup
at right up stream of the injection septum inflector withoutchanging any parameters from the design values.
A multi-turn injection is performed with four bump magnets. Injection beam and pulse of the bump magnets are

2.3

RF Acceleration

The frequency of RF acceleration is determined by the circumference of the ring, energy of the beam and the mass.
The frJ for the flat top and the flat bottom which arecalled t-clock regions are set to constant frequencies. In
the acceleration and deceleration regions which are called
b-clock regions, the frequency patterns are determined by
the derivative of the bending magnet field. The RF cavity
is ferrite loaded tuned type. The harmonic number h = 3.
The minimum frequency is 0.993MHz which corresponds
to 5MeV proton beam, and the maximum is 6.417MHz for
320MeV carbon beam. Fort-clock regions, we give ·appropriate frequencies from the MMI terminal. On the otherhand, for b-clock region, data array of frequency as a function of BM field is provided. The pointer of the array isincremented if one pulse comes from the b-clock pulse generator which generates a pulse when the magnetic field ischanged by 0.2 gauss. The initial value of the frequency
in the b-clock region is chosen so that the difference fromthe frequency in the t-clock region takes minimum. At thetransit from b-clock to t-clock, if there is a frequency gap,
they are connected linearly at a fixed rate. It has been set to
2.8kHz/ms.
The RF frequency and the bending field at the flat bottom
is adjusted for the injector energy so that the incident beamcan circulate at the center of the beam duct. At the flat top,assuming that circumference of 93.6m is correct, the RFfrequency is calculated for each required extraction energy.
Then we determine the bending field so that the orbit isat the center. At this time, COD should be corrected. To
measure COD I2 horizontal and II vertical beam position
monitors are used. And to correct COD I2 horizontal andI2 vertical steerers are used. All the quadrupoles except
for one QD at the beam extraction section has a set of a
BPM and a steerers in the neighborhood[3]. By the best-173-The .J3th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

I

corrector method, COD at the maximum of 25mm has beensuccessfully corrected to the maximum of 2mm at the flatbottom and 5mm at the flat top.
The beam is captured 3.5ms after injection changing theRF voltage from OV to 200V within 0.7ms. The RF voltage
is kept at 200V until smoothing starts. It raise up to 3kVduring 50ms smoothing, and is hold at 3kV all the time
region after smoothing ends. The capture voltage and themaximum voltage have been optimized from precise beamtuning to minimize beam loss. Capture and acceleration
efficiency is summarized in Table 2. In the case of 320Me V
carbon, a typical beam signals are shown in Figure 5.

Septum electrode at 71 mm

0.01\~\\'· \ \\\\ ..

\0\\.\.

~~~.

'•-0.01

-0.05

00.05

0.1

Figure 6: The optimized separatrix obtained by beam tuning.

Table 2: The efficiencies of RF capture, acceleration, extraction and the number of particles for each beam species.
BeamProton
Figure 5: Typical acceleration and beam extraction figure
for 320MeV/u carbon beam.

2.4Carbon

Energy
MeV/u
150
190
230
250
320

Cap. eff.

Ace. eff.

%%

Ext. eff.
%

50.9
51.9
49.1
88.9
86.4

83.5
89.0
91.7
91.1
92.6

89.6
81.9
91.4
98.5
82.6

Number ofparticles PPI
7.62x10 107.56x10 108.85x10 103.62x109
3.95x109

Slow Beam Extraction

The beam is extracted from the ring by using third orderresonance slow extraction method to obtain spill length of400ms. The natural chromaticity of (-4.1,-3.0) has beencorrected to (-0.2,-5.8) by focusing sextupole SXF. For thetuning of beam extraction, main focusing quadrupole QF,resonance exciter SXFr, SXDr and orbit bumper BMPl4 are utilized to adjust the separatrix in the phase space.
Figure 6 shows the optimized separatrix obtained after thetuning. It is the case of 150MeV proton beam.
The extraction efficiency and the number of particles foreach beam species are shown in Table 2. These were measured at the beam stopper installed in the high energy beamtransport line.

the tolerance by adjusting the steering magnets in the transport line.

3 SUMMARYIn Heavy Ion Beam Medical Center, three kinds of protons,
two kinds of carbon, and a total of five kinds of operation
patterns are performing supply operation for clinical trial.
The beam intensity of 2 Gy/min has been attained for every operation pattern. Operation with the intensity up to5Gy/min has been permitted since April2001. Because thereproducibility of the machine is good, daily adjustment isalmost unnecessary.

REFERENCES

2.5 Daily Operation
Machine operation for clinical trial has been carried out
since May 2001. It is run by two operators. They areperforming not only the synchrotron but operation of theinjector or beam transport systems. Adjustment for thesynchrotron is usually unnecessary. On the other hand, ingantry rooms, a drift of the beam axis exceeding the tolerance of 2mm occurs occasionally. Then it is made within[1] A.ltano, in these proceedings.
[2] T. Kokubo, et al., Proc. 12th Symposium on Accel. Sci. Tech.
Wako, Saitama, Japan(1999), pp.447-449.
[3] Y. Yamamoto, et al., Proc. 12th Symposium on Accel. Sci.
Tech. Wako, Saitama, Japan(1999), pp.507-509.

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