The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

Vacuum System for the Cooler Ring TARN2
Katsuhisa CI-IIDA *, Tetsumi TANABE"*, Yoshitsugu ARAKAKI*, Tamaki WATANABE*,Shinpei ONO+, Morio YOSlllZAWA* andichiroKATAYAMA#**High Energy Accelerator Research Organization, Accelerator Division, Tanashi
3-2-1, Midoricho, Tanashi, Tokyo 188, Japan+Tokyo Institute of Technology, Meguro-ku, Tokyo 152, Japan#Center for Nuclear Study, University of Tokyo
3-2-1, Midoricho, Tanashi, Tokyo 188, JapanAbstract

2 Pump system

A new type Non-Evapmable Getter (NEG) pump wasresigned to obtain a better vacuum pressure in the cooler
ring TARN2. This pump is activated by a mantle heaterfrom outsire of the pump chamber. With this pump, anaverage pressure of 1xlo-s Pa has been achieved Wring thebeam time of atomic physics experiments. Change of thevacuum pressure in the ring from 1988 to 1997 is alsopresented.

The TARN2 ring has a circumference of 78 m and ishexagonal in shape with six long straight sections. In thestraight sections, electrostatic intlectors for the ion injection (Straight section:S 1), ad: current tmnsformer and abump magnet (S2), nonrestructive profile monitors (S3),an electron cooling revice (S4), an rf knock out electrore(SS), an rf cavity and a bump magnet (S6) are located. Thevacuum chamber at the electron cooling section can beisolated by a pair of all-metal gate valves. Stain less steel
316L was used as the material for vacuum chambers.
The pump system consists of Titanium Getter Pump(TGP) , Ion pump (IP) and Turbo-Molecular Pump (TMP).
TGP and IP were located in straight sections and dpolemagnet chambers. Total pump speed ofTGP andiP after
the first up~ in 1991 was 30000 1/s. The turbomolecular pumps with a pumping speed of 500 lis are
installed at the long stmight sections of S 1, S3 and SS.
Roots pumpslocatedat S3andS5 areusedonly atthetimeof pumpingdownfrom the atmosphericpressureinorderto
evacuate quickly in the intermediate flow region.
The pressure was measured by B-A type ion gauges.
Quadrupole mass filter was used for the resiillal-gas
analysis. The pump system of the ring is shown in Fig. 1.

1 Introduction
The cooler/synchrotronforlightandheavyions with anelectron cooling system,TARN2 was constructed for thestudy of accelerator technology in 1988. Experiments on
the electron cooling, the beam extmction and the beam
acceleration were successfully performed 1·3 l.
In early years, only the vacuum pumps used at theformer storage ring TARN! were available to evacuate thevacuumchamberofthering. In 1991, thefirstupgradeforthe pump system at TARN2 was performed by newly
adling titanium getter pumps and sputter ion pumps inorder to promote the study of atomic physics. As a result,an average vacuum pressure on the order of 10·8 Pa wasachieved d:tring the beam time4l. However, a further better
vacuum was required to obtain sufficiently long beam times
for collision experiments between molecular ions andelectrons. Torealizethepurpose,a furthertrial wasmadetoimprove the vacuum by utilizing a new type NEG pump.
For the atomic physics experiments, molecular ionssuch as HD/, HeW and ReD+ were injected in the ring andan average vacuum pressure of lxl0-8 Pa was maintained
illring the beam time5l. History and status of the vacuum
system at TARN2 are also reported.

3 NEGpumpIn advance of the second upgmre, we measured theperformance of the ion pumps used in the ring by the buildup method The result of experiments suggests that theseion pumps are still useful for the pumping of rare gases andmethane in 10-8 Pa region. Therefore, the pumps having ahigh pumping speed for hydrogen gas was mainly required.
As a result, the new type NEG pump reveloped at Stockholm6) was chosen and newly adled. This pump is heated-365-

The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

from outside of the pump chamber by a mantle heater. Jheactivation by heating from outside is r~onable because it
removes molecules on the swface of the pump chamber
along with the activation.

• : BA gaugt: Utanlum stJbllrnaUon pump:turbo~moleocularli!il: root pumpg]:

4 Application of the NEG pump to the system
Thirty-oneunits of this pump were installed in the ring.
A sum of pumping speedof the NEG pumps for hydrogenamounts to 12000 1/s. This value means the increase by
40% of the total pumping speed after the ftrst upgrade. Inthe section S3, more NEG pumps (eight units) wereinstalled in comparison with those at other sections,because non-destructive beam profile monitors which must
bekeptata low temperature of about 100°C during baking
was located in this region.

TARN.- II~ : sputter lon pumpof the NEG pump is shown in Fig.2.

pumprotary pumpvain

N:®: NEOpump

NEG AliVATION

52II-•

C3••• ••••Fig.l The pump system for the TARN2.

• •• .... • •••BAKING

to·'...

••to·s051015.TIME (DAY)2025Fig.3 Pumping-down curve at S3 chamber.

Fig.2 Photograph of the NEG pump.
This pump has cylindrical shape with a diameter of 100
mm anda length of a300mm and is mounted on aCF 152
flange. 24leavesofNEGstrip (whichare30mmwide,269
mm long and 0.5 mm thick) are insertedinto the cylinder.
Low temperature type S1707 NEG strip which has activation temperature of 400°C is used A pumping speed of
400 11 s for hyd-ogen is expected at one pump after activation at 300°C for 30 min6>. During operntion, the mosteffective activation process was investigated PhotographPumping-d>wn curve at S3 chamber in the ring isshown inFig.3. Baking was performed with sheath heaters
at temperatures of350°C (TGP), 250"C(IP) and 100-300°C(chambers). Dipole magnet chambers were baked by a decurrent passage through the chamberwalls around the ring at
1000 A The temperature was 150°C in the central part: ofthe dipolechamber. Baking time as long as eightdayswere
needed for sufficient outgassing treatment, because gas load
exceedng the pumping speed of TMP was imposed bybaking. Baking temperature was controlled by slide regulators to keep the vacuum pressure lower than the order of
10-3 Pa. We aimed to get a vacuum pressure of the order of10-5 Pa at the end of the baking when the full heaterpower
was supplied. Activation of NEG pump was performed after
three-days heating at 150"C and at the end of all baking
process by gradually stepping up to 400°C during 30 min.

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The II th Symposium on Accelerator Science and Technology, Harima Science Garden City, I997

to·'Fig.4 shows the vacuwn pressure at S3 after the ftrst
upgrade in 1991. The pressure graWally decreased to theorder of 10-9 Paafter the second upgrade by NEG pumps in1994. It was found that this type NEG pwnp is useful toour system.
Mass spectrum of the residial gas at S3 is shown inIP,TGPNEGat SJl...0 PressureAtmosphereI~~ '@Fig.5. About 95% of H 2 and a few% of CO, C02, ~andHP are observed.
The change of the vacuwn pressure at the beam timefrom 1988 to 1997 is shown in Fig.6. The pressures havebeen measured at eight positions in the ring. A lie beam
life time of3 sec was measuredfor 4HeH+ (12.5MeV) at anaverage vacuwn pressure of 1x10-8Pa.

~to·'uc lllQO C!
'0 IllSt99t t992 t993 t994 t995 t996 t997
Time (year)

4 Conclusion
The new type of NEG pumps activated from out-sideof
the pump chamber was successfully applied to the cooler
ring. The average vacuwn pressure of 1x10·8 Pa has been
maintained Wring the beam time of atomic physics experiments.
Features of this type of NEG pump are summarized as''6~00

Fig.4 Vaeuum pressure at S3 before and after upgrade by
NEG pump.
I;

,.

I

P=3.8xiO''Pa"·
COIN,follows;(1) Simple structure without ceramic feed-through foractivation.
(2) Effective outgassing of absorbed molecules on the innersurface of the pump chamber during activation.

co,CH4 H,Ox10; . l''Ii

Ii,IiI I!: IM/e216 182844

Acknowledgment
Fig.5 Residual gas spectrum at the S3 chamber.
The authors are gmteful to members of cyclotron stuff;
T.Yamazaki, M.Fujita, Y.Ohshiro andN.Yamazaki.

PRESSURE AT BEAM TIME.
10...

.,

~N!GIP,~!P(X

References... At111osphere

10"[1] T.Tanabe et al., Nucl.Instrm. A307 (1991)7.
[2] M.Tomizawa et al., INS-Rep.-954 (1992).
[3] T.Katayama et al., INS-Rep.-945 (1992).
[4] K.Chida et al., Vacuum 47 (1996) 633.
[5] T.Tanabe et al., Phys. Rev. Letter 75 (1995) 1066.
[6] L.Bagg et al., Vacuum 44 (1993) 497.

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eli"'~to·•~!Sx

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0LowestX

Highest Yaluevalue

X
X~~ ~~ ~.
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X

Beam extraetfon~0~ ~$000~~JS;oo ~;o/rm TcelerarXX'~· ...

~~X~~lj ~)J\Cj £liP~~~00~01991

1993 1994

P"•q ~~~~ g~~ ~GO .. ~1o·•
1!188 1989 1990

199~

1995 199,

TIME (YEAR)

Fig.6 Change of the vacuum pressure at beam time.

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