BEAM TRANSPORT AND INJECTION SYSTEH AT TARN II AND TEST OF MULTITURN INJECTION
F. Soga, K. Noda*, K. Chida, T. Hattori*•, T. Honma, T. Katayama, A. Hizobuchi,
H. Nakai**, A. Noda, F. Sakuta, H. Sekiguchi, N. Ueda, S. Watanabe, and M. Yoshizawa

*
**
***

Institute for Nuclear Study, University of Tokyo
Midori-cho 3-2-1, Tanashi-city, Tokyo 188, JapanThe Japan Steel Works, Ltd. Tokyo Research Laboratory
Nikko-cho 1, Fuchu-city, Tokyo 183, Japan•
Research Laboratory for Nuclear 'Reactors, Tokyo Institute of Technology
Ohokayama, Meguro-ku, Tokyo 152, JapanNKK Corporation, Kumozukohkan-cho 1, Tsu-city, Mie 514-03, JapanABSTRACT

Beam transport system from the INS-SF Cyclotron
to the 'TARN II' Synchrotron Cooler Ring was designedand constructed. In the present paper, design conception and characteristics of the system as well as theeA~rimental results of the multiturn beam injection
are described.
INTRODUCTION
On the basis of the achievement of the accelerator 'TARN' , the bigger scaled ring called 'TARN
II' is constructed, aiming at the new development ofaccelerator technology and its utilization of the beamfor experiment. The upgraded ring will be operated as
an accumulatar, accelerator and cooler. The ring
diameter is about 25 m and maximum energy is 1100 MeVfor proton and 350 MeV/u for other light and heavy
ions with charge to mass ratio 1/2. The detailed
specification of the ring is described in the otherpaper in this conference.'
The SF Cyclotron is used as an injector for thisring. The Hhole system linked between the Cyclotron
and the TARN II ring is shown in Fig. 1. From theCyclotron to the entrance of the TARN II room, theconfigurations of all the optical elements and devices
such as magnets, and slits etc. are not alterd.• In
contrast, the transport line in the TARN II room arethoroughly changed, which matches the ring TARN II.

change of optics in the downstream.
(7) In order to make the kicker magnet for beam pulsing system operate effectively, the horizontal beamwidth at the associated slit position should bereasonably small.
The beam injection line in the TARN II room is
illustrated in Fig. 2, comprizing the following optical elements ; four window frame-type bending magnets3(BTl~ BT4), a C-type bending magnet (CM), four quadrupole singlets (QS1~QS4), two quadrupole doublets(QDA,QDB), a quadrupole triplet (QTA,QTB,QTC), twopairs of steering magnets (ST1,ST2) and an electrosTotal length of the line fromtatic inflector (IF).
the exit of the SF Cyclotron to the entrance of thering is 53.7 m.
The beam optics parameters are calculated using
the program 'MAGIC'. The initial and final conditions
for this calculation are summarized in Table 1. The
initial conditions are the measured values of theemittance and the momentum spread of the beam extracted from the SF Cyclotron. The final conditions
are so chosen that the beam matches to the injection
condition corresponding to the TARN II operationmodes. Three different modes are considered. As theSF Cyclotron can provide the beam of the maximum magnetic regidity of about 1200 kG· em, that is regarded
as the upper limit of characterizing beam momentum inthe transport line. Among the different modes, one of
the results in the calculation of the beam optics isshown in Fig. 3.

DESIGN OF BEA~ TRANSPORT SYSTEM
The ultimate objective of the transport line isto obtain the good efficiency of the beam transmission
and to match the optical condition of the beam injection into the main ring.
The design principles of this line are as follows.
(1) Beam is to be transported with the smallest loss.
(2) A doubly achromatic section is to be prepared forseparating the optics of transport line up to the cave
2B after the SF Cyclotron from the injection
parameters for TARN II operation modes.
( 3) The Twiss parameters of the beam at the entranceof the ring is easily adjustable to match the condition of the different modes, which facilitates themultiturn injection.
(4) The beam size at the intersecting point with theTARN II ring is to be less than 15 mm in diameter.
(5) At the narrow gap of the inflector the exit ofwhich is placed horizontally parallel to the closed
orbit of the main ring, the dispersion function
should be as small as possible.
( 6) As the arrangement of magnets in the upstream
section from the SF Cyclotron is not changed, themomentum analysing section is the same as before, but
the parameters of several Q magnets after the BA4 magnet in the cave 2B are adjusted in accord with thePresent address : National Institute of Radiological Science, Anagawa 4-9-1, Chiba 260, JapanFig. 1-276-

Layout of SF Cyclotron and TARN II.

(Mr'----------------------------------------,The initial and final conditions

Table 1101) initial c9nditions(kG· em)max. Bp
momentim spread ~PIP
90% emittance(mm· mrad)
Twiss parameters(m)
13a(m)

17a x
1'/ X
1'/(m)

13 y(m)

a Y

Hori.
15n:

Verti.
15n:

1.176-0.7760.73

0.385
0.00.0Synch.
1. 75
1.25Synch.
2.25
2.25

Cooler
1. 75
1. 25

0.6
0.0
0.0

0.6
0.0
0.0

7.35
-0.24

3.27
-0.82

0.6
0.0
0.0
0.0
3.60
-0.61

o.oo.o-5--~------~-10_'If •(M~)--------------------------------~------~

sor--------------------------- -------------,

o.o

o.o

1'/

2) final conditions
operation mode
hori. tnne v xvert. tnne v yTwiss parameters
(m)
13 X

1200± 7x 10-•FOWER SUPPLY AND ITS CXlNTROL

Each power supply for electromagnetic elements
described above, is operated in two different ways.
From the exit of the SF Cyclotron up to the first
quadrupole magnets QDA along the transport line, all
the power supplies and their control are operated in
the control room of the SF Cyclotron. In contrast,
the control of various elements in the TARN II room isoperated in the newly allocated 'TARN II control

1020BAlrn uij o 11room'.

All the power supplies for the optical elementsin the TARN II room are operated by way of digitalsystem. This is adopted because the long distance between the location of the power supplies and control
room (80 m) gives advantage to transmission with digital signal than that with analog signal, considering
the large noise caused by the radio frequency cavity
or time-varying excitement of the magnets in the ring.
The power supplies in the injection system arecotrolled and operated by use of the 16 bit microcomputer M16 and this is further linked to the minicomputer U400.
The CAMAC serial highway system is employed toregulate the power supply. The extended control boxes
which are regulated with the CAMAC module, provide 10channel digital-to-analog converters with either 12 or16 bit resolution. To regulate these boxes and forfurther control and monitoring for each power supply,
a 'process controller' of CAMAC module has been fabricated.
As a man-machine interface, a touch panel system
is employed to regulate the control, where a rotary
encorder system is used for smooth adjustment of setting parameters.•

1530
25
ORBIT .LENGIH

BTlBA4DO !!

35

50

45

40

IMIBT2BT3

BT4 Qlmum~1m1o m~~ 0Fig. 3(a) Dispersion function 17 and its derivative
17 ' and beta functions 13 x, 13 y •(b) Beam envelopes (horizontal and vertical)
along the transport line.
OONITORING DEVICES
At every section after each bending magnet, thebeam monitor system is placed as shown in Fig. 2.
Several different types of beam monitoring devices areused. In addition to the beam dump slit(Sl5) andprofile monitor (P14), emittance monitor (EM), andhorizontal slit stopper (HS), the newly fabricatedmonitors are the rod-stoppers (RSI and RS2) whichenable to measure both the beam profile and current.
A quartz viewer is placed just before the gap ofinflector to assure the final beam spot in the line.
20Fig. 4 Gain of multiturn injection versus
damping time constant ofof bump field.
(a) ~PIP= 015z~ 10Injection Line(b)~PIP=0.1%

(c)

~PIP

= 0.2%

TINE CNST. I REV. TL"1EVACUUM SYSTE!'l

Fig. 2 Transport and injection line in the TARN IIroom. See the text for each element.

As there is a intersecting point with the ring at
the middle of the transport line, the vacuum system of
the new transport line is designed such that the ductand chambers can be bakable and powerful differential
pumping system is provided. So far, 2xlO-• torr isobtained between magnet BT 2 and BT 3 even withoutbaking. It is expected to reach much better vacuum byforthcoming baking procedure.

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SCHEME OF TilE MULTI11JRN INJECTION
In order to obtain higher beam intensity in theTARN II ring, the multiturn injection method is applied. I t consists of the inflector which separates
the transverse phase space in the injection beam linefrom the acceptance of the ring and t1-10 bump magnets
which displace the closed orbit. For an efficient
multiturn injection, a detailed simulation study has
been performed. 5 The distance of the electrode whichcorresponds to the maximUITI beta oscillation amplitude
at the injection point is set horizontally 70 ITIITI apartfrom the central orbit. The two bU!Tip magnets (BGM 1,BUM 2) are positioned apart from each other at half ofa wave length of horizontal beta oscillation as shmmin Fig. 1.
The horizontal emittance of the injection beam isassU!Tied 15n: (ITIITI • mrad) based on the measurements ofthe extracted beam from the SF Cyclotron and eachparameter used for the calculation is listed in Table
2. The acceptance of the ring in the horizontal phasespace is taken to be 300n: (ITIITI • mrad). The derivativeof the horizontal beta function of the injection line
is to be zero in order to fill a beam with horizontal
phase space as much as possible. The vertical beta
function and its derivative in the injection beam line
are to be matched with those of the ring to avoid abeam dilution. On the other hand, the dispersion
function and its derivative for the injection beamline are designed to be zero at the injection point inorder to pass the beam through the gap of the inflector, while the dispersion function for the ring is 4.6
m in the same point.
On the assumption that the fields of bump magnets(maximum field 500G) are exponential dU!Tiping, a sizeand collapsing speed of the distorted closed orbit are
optimizes in accord Hith the beta functions in theinjection beam. The gain of multiturn injection invarying the dU!Tiping time constant are illustrated inFig. 4.
The cyclotron beam is operated in continuous wavemode, Hhereas the ring can accept these bunches invery short period. Therefore, the beam pulsing systemin the injection line is installed in the cave 2B,comprising a kicker magnet, two quadrupole magnets andtwo steering magnets. The magnetic field has roughly
a rectangular waveform of 10~ sec in rise and falltime, 60~ sec in width of the flat top, and about 180
gauss at maximum in field strength.
Table 21)

Parameters used in the simulation.

Fig. 5 (a) Timing relation of monitoring signals
from above, the arc of the ion source in pulsed operation, discharge current of kicker magnet and those ofbump rr~gnet 1 and 2. Horizontal scale is 50~ sec/1div.
(b) Signal from electrostatic monitor. horizontal
scale is 2 msec/1 div.
PERFORMANCE ON BEAM TRANSroRT AND INJECTION
At the beginning of 1989, the first experiment ofmultiturn injection into the ring was carried out Hiththe pulsed beam of 28 MeV a particles. At the exitof the SF Cyclotron, the beam emittance was measured
at 15n: ITIITI• mrad (horizontal) and 20n ITIITI• mrad(vertical), respectively and momentum spread was 0.2%.
The one third of the beam was transported to the injection point of the TARN II. Since then, several
times, multiturn injection Here tried by using either
28 MeV a or 20 MeV proton beams. Usually pulse
width and the repetition rate at the ion source were 3
msec and 30 Hz,. respectively. The beam was multi tum
injected into the ring with the excitation of two bump
The decay time of bump fields was set tomagnets.
approximately 40~ sec which corresponds to about 20-30
times of revolution period of the beam in the ring.
The frequency of RF field was set to be the value corresponding to the harmonic number 2 of the beam circulation (1.587 MHz in case of proton 20 MeV). InFig. 5, the signal from the beam monitor is given
together with monitoring signals of pulsed arc in thecyclotron, discharged currents of kicker magnet andthose of two bU!Tip magnets. From the signal of theelectrostatic monitor through the Intermediate
Frequency (0.455 MHz) amplifier, the gain of intensityof the circulating beam can be seen to increase by
about 14 turns, which realizes quite well the ex~ctedvalue of the simulation. The life time of the stored
beam was measured in that case to be 12sec.

Parameters of the injection beam
15n: (ITIITI • mrad)0.2nr- 0. 7m

E ;Emittancefl;
Beta functiona;its derivative
Dispersion function
7J;
its derivative
7J;/:,.PIP
Momentum spread2)

(b)

(a)

000o~

o.2%

Parameters of the ring at injection point
Horizontal tune
Beta function
its derivative
Dispersion function
its derivative
AcceptancePhase advance between
two bump magnets
Phase advance frombU!Tip 1 to injectionpoint
septum thickness

VX

fJ Xa x
7J X
7J X.

Ax/::,.~

1. 75
9.06m
-0.18
4.55m
0300n (ITIITI • mrad)1.05n:

8 v

0. 58n:t

0.5!TIITIACKNOWLEDGEMENT
The authors ex~ress their sincere gratitude toProf. Y. Hirao for his continuous encouragement. They
are indebted to Mr. Mizutani and other staffs of themachine shop in the institute. The simulation is performed with use of FACOM M380 at the INS computer center.
REFERENCES
1) T. Katayama et al., "Present status of cooler
synchrotron TARN II" presented in this conference.
2) T.Hattori et al.,INS-NUMA-25(1980)
3) T. Hori et al.,INS-NUMA-24(1980)
4) S. Watanabe and M. Takano, INS-NUMA-56 ( 1984)
5) K. Noda et al.,Proceeding of the 1987 IEEE
Particle Accelerator Conference P1275.

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