PRESENT STATUS OF TARN-II VACUUM SYSTEM
K. Chida, A. Mizobuchi.
Institute for Nuclear Study, University of Tokyo
Midori-cho 3-2-1, Tanashi-shi, 188 Tokyo, JapanVacuum chamber

Abstract
The vacuum system for new cooler/synchrotron,TA RNAll vacuum
II, was constructed in the fall of 1988.
system is designed in the condition of the organic freeNow, the pressure ofand is bakable up to 350•c.
4x10-1°Torr is achived at good region.
Introduction
The heavy ion cooler/synchrotron,TA RN-II, was conThis ring has the performance
structed in 1988.
which accelerates ions up to the energy of 1.1 GeV for
protons and 370 MeV/u for heavier ions with the charge
The ring has
to mass ratio of 1/2, respectively[1-5].
mean radius of 12. 4 m and circumference of 78 m and has
24 dipole magnets and 18 quadrupole magnets, and 6 longstraight sections in which beam injection, extruction,
electron cooling device and rf cavity are located.
The vacuum pressure better than 10-10 Torr isrequired to obtain long life time of heavy ions forbeam storage and cooling experiments at TARN-II.
In order to keep the pressure lower than 10-1•Torr,the out gassing rate from the chamber wall must beThen the vacuum system is fabrireduced to minimum.
This constitucated with the organic free materials.
tion is efficient for the high temperature baking.
Low out gassing rate lower than 1x10-12Torr·l/s·cm• was
already obtained by baking experiment of thechamber[6], so the required pressure will be obtained
after high temperature baking.

Operation mode of TARN-II is planed rather slow
acceleration period as 0.1 Hz, so the vacuum chambers
as dipole and quadrupole magnets are used 3161
Thein thickness.
stainless steel plates of 4mm
vacuum chamber which correspond to two stage of thedipole magnets has 3 m in length and has cross sectional area of 240 mm (horizontal) x 53mm (vertical).
The vacuum pump port and auxiliary port are located in
The flange of the boththe middle of the chamber.
side of the chamber are 325mm in diameter and thestainless steel 0-ring gaskets coated with silver are
Layout of the chambers are shown in Fig. 1.
used.
The vacuum chambers of the quadrupole magnets havediamond shape of cross section of 190 mm (horizontal) xThe bump mag90 mm (vertical) and 460 mm in length.
net chambers are made from pure alumina ceramics andits cross sectional area is 190 mm (horizontal) x 33.5
The chambers ofmm (vertical) and 520 mm in length.
the ring are connected by mainly conflat flanges withoxygen free copper gaskets and partly metal 0-ring seal
and helicoflex seal are used.

-Design and construction of the vacuum system
Basic

Q-M

O-M

D-M

design of the vacuum system

TARN-II is operated as heavy ion storage ring, so
the vacuum pressure of better than 10-10 Torr isthe vacuumrequired to keep long beam life time.
system was designed on the basis of following points.
1. Organic free materials as stainless steel andpure alumina ceramics are chosen for vacuumchambers.
2. All vacuum chambers are bakable at 350• C.
3. All metal gaskets are used and elastmer is notused.
4. Ion pumps, Titanium sublimation pumps andTurbo-molecular pumps are employed.
Table 1
Parameters of the TARN-II vacuum system
Circumference
Total surface area
Required vacuum pressure
Total pump speed
Titanium sublimation pumpSputter ion pump
Turbo-molecular pump
Out gassing load (Required)m78
5 X 10 5 cm 2
< 1 X 10- 1 0Torr
1.7x 10 4 1/s
1500 X 7800 X 5400 X 3500 X 3

@+=-·

.

t·.
:-L.J:sr~·....

0on . ..,::1

< 2 x 10- 6 Torr·l/s

Out gassing rate (Required)< 4 x 10-12 Torr·l/s·cm 2:~!

240.

t

Fig. 1 The chamber of the dipole magnet section.

-139-Pump svstem
The parameters and arrengement of the pump systemof TARN-II are shown in Table 1 and Fig. 2.
The ionpumps of 800 1/s and 400 1/s and the titanium sublimation pumps of 1500 1/s are assembled to pump ports ofthe dipole magnet chambers.
The ion pumps of 800 1/s
are equipped at inflector chamber, S1, and beam crosspoint of TARN-II ring and transport line for the

purpose of reinforce of pump speed.
The turbomolecular pumps of 500 1/s are located at 81, 83 and 85
correspond to symmetrical position of the ring.
Themechanical booster pumps are equipped in roughing pumpstation of 83 and 85 in order to reduce back diffusionof oil vapour.
Vacuum pressure of the ring is measured byBayard-Alpert ionization gauges with modulator and thegauges are equipped with near pump ports of the dipole
magnet chamber.
The residual gas of the chamber ofthe ring is measured by quadrupole mass analyzer.

The chambers of the dipole magnets are baked bymeans of supplying DC current through themselves, so
the all chambers of the ring are insulated electricalyfrom the ground.
The baking of the other chambers
and the pumps are done by sheath heaters or mantle
heaters.
The glass wool sheets of 25 mm in thickness
are used for the heat insulation of chambers.

-104.2 •10~co;az

LEGENDEi : sputter ion pumpg

e: turbo-mclei:ular pump

M/e 2:tEl: titanium sublimation pump~:root pump&:J: rotary pump
N: valve

Fig. 428

18The residual gas spectrum of the TARN-II.

,(l.-----------------,The vacuum system of the TARN-II.

20MeV, P

1~r----------.----------r----------r---,T l/e= 12 sec

Fig. 2

Torr

PUMP DOWN CURVE(TARN-II)

P= 2 x 11)9 Torr-- · · - - .. - 0 . . - _ .. _ _ _ .. __o.. - -.. -lU!§VlVl~109 -

00-.

ll.

0-1010 ~1re;;]

r.;;;t~ 1 2~3 4 §1;:;;15 6 ~ 7 8 ~ 9 10 ~11 12Gauge posit JonFig. 5

The vacuum pressure of the TARN-II at the beam
experiment.
Results and Conclusion

200

400600

PUMP DOWN TlME (HOUR )Fig. 3The pump do'm curve of the TARN-II.

A characteristic of typical pumping down is shownin Fig. 3 and the vacuum pressure has attained to 4 x
1Q-lOTorr at good region.
The vacuum gauge settled
at six position around the ring are indicated the value
betJ.;een 2xlO-• to 4xlO-IOTorr. Also, a spectrum of theresidual gas is shown in Fig. 4.
For example, thevacuum pressure at beam e:>-tJeriment is shown in Fig 5.
In this time, the beam life time of 12 sec was measured-140-

from the beam acctnnUlation e}>.-periment for 20 MeV proton
beams. The beam signal of the electrostatic monitor isshown in Fig. 6.
From the beam life time, the averagepressure is estimated at 2 x 10-• Torr.
At present, the baking process does not applied tothe vacuum system except pump stations.
The requiredvacuum of the order of 10- I I Torr will be attained
easily after high temperature baking of 3oo•c.
The following important problems about vacuum system must be equipped:

Acknowledgements
The authors would like to express their thanks tomembers of Accelerator Research Division, Institute forNuclear study, University of Tokyo and Mr H. Tsujikawa,Japan Steel Works for their collaboration.
We arealso grateful to Professor Y. Hirao, National Instituteof Radiological Science.
References1) Application of the high temperature baking of 30~C.
2) Well-equipped centralize controle of vacuum system.
3) Improvement of differential pumping system at thebeam transport line.

Fig. 5

1. Y. Hirao, 'Operation of TARNJ , in IEEE Trans, Vol NS
28 2086 (1981).
2. T. Katayama, 'Beam accumulation and cooling at
TARNJ ,inProc.10th Int.Conf. on Cyclotrons andtheir Applications,(1984) p 595-600.
3. K. Chida, A. Mizobuchi, H, Tsujikawa, T, Morimoto,
K. Kaneko,and A. Miyahara. Proc. 2nd Symp. onAccelerator Science andTechnology. (1978) p 35.
4. H. Tsujikawa, K. Chida, T. Mizobuchi andA. Miyahara. 'Vacuum system for the Test AcctnnUlation Ring for Numatron project (TARN)J Proc. 8thInternational Vacuum Congress (1980) p 151.
5. T. Katayama, 'Heavy Ion Accelerator and Cooler
TARN-IIJ,
Proc. 11th Int. Conf. on Cyclotron andtheir Applications, (1986), Tokyo, Japan p 128.
6. K.Chida, H.Tsujikawa and A. Mizobuchi. 'Vacuum
System of TARN-IIJ Proc. 6th Symp. on Accelerator
Scienceand Technology. (1987) p147.

The beam signal of the electrostatic monitor.
The scales are 2 sec/div (horizontal)
and 2 v/div (vertical).

-141-