+ - COLLIDING BEAM RING

ALL-ALUMINUM ALLOY VACUUM SYSTEM FOR TRISTAN e e

H. Ishimaru, T. Momose, K. Narushima, H. Mizuno, K. Kanazawa, H. Watanabe and M. Shimamoto
National Laboratory for High Energy Physics, Oho-machi, Tsukuba-gun, Ibaraki-ken, 305, Japan
ABSTRACT
Design and cons~r~ction of all-aluminum alloy vacuum
system for TRISTAN e e colliding beam ring has beenpresented.

The rf insert made of Be-Cu, 0.35 mm in thickness isinstalled in the bellows to prevent the parasitic modeloss due to bunched beam. The surface of the aluminumalloy bellows is anodized to protect the corrosion due toNOx.

Straight section chamber
For the rf sections and the experimental regions,the aluminum alloy(6063-T6 -EX) circular pipes are used.
The first truely all-aluminum alloy vacuum system
Fig. 3. Tapered vacuum chambers are inserted between thefor large scale electron-pos itron colliding beam ring is
racetrack and circular chambers for smooth wall current
The construction of the accumulatiop _fing
described.
flowing. The vacuum chamber for the septum magnet ismade of all-aluminum alloy was completed in 1983. 3
fabricated from the modified quadrupole magnet chamber.
Electron beam was accelerated and stored 6.5 GeV. We
4. Thickness of the wall of the septum side is 1 mm.
Fig.
vacuumall-aluminum
theinessentiallyhave no problemof the injection is the beryllium foil whose
window
The
basicarecomponents
itsandsystem. The vavuum systemthickness is 0.3 mm. Since the injected beam line isally the same as one of the accumulation ring. Much
located inside of the ring, the moving mask against the, effort were paid to minimize the free space between thesynchrotron radiation for Be window is not required.
bending__a_ncLthe quadrupole magnets. Maximum line power
A ceramic chamber is bonded to aluminum alloy bellows
density of the synchrotron radiation along the beam pipewith a brazing sheet(4343-30 03-4343) inpieces(3003)
itron
electron-posmA
7mAx
7GeV,
30for
is 1.3 kW/mvacuum furnace. For the metallization Mo-Mn with Nibeams. The critical energy of the synchrotron radiation
bellows isis 256 keV and the penetration range is 34 mm for aluminum. plating is used. The ceramic chamber withwelded directly to the aluminum alloy chamber. This type
Required operating pressure with beam is 5 x 10- 9 Torr.
of ceramic chamber is used for the kicker magnet chamber
and the beam intensity monitor. The inner size of theBEAM CHANNEL
ceramic chamber of the kicker is 92 mm wide and 54 mm
in racetrack shape and 600 mm long. The inner
highchambermagnets
Bending and Quadrupolesurface of the ceramic chamber is coated with Ti-Mo for
The aluminum alloy(6063-T6 -EX) vacuum chambers insmooth wall current flowing. Fig. 5.
the bending and the quadrupole magnets are designed soas to accomodate the required beam clearence region andGate valve
to allow an automatic welding between the chamber and a
By relying on differential pump.ing between dual flat
racetrack type bellows. The thickness of both chambers
seals , we developed a gate valve which has no gasface
pumpingline
doublehasmagnetbending
Themm.
4
isknife edges. The sealing surfaces of the isolatingor
keteffecThepitch).
mm
60andlongmm
40slits(4 mm wide,plate are polished to a smooth mirror like finish by ative conductance of the slits is 250 1/s m. The curhardening. The
vature of the bending magnet chamber is 250 m. In bending flat diamond tool and coated with CrN for
valve seats, which are 0.1 mm thick aluminum, are pressedand slit punching process of the bending magnet chamber,by compressed air against the sealing surfaces. A closethe beam chamber was filled with the argon and oxygen
contacting, metal surface seal is obtained. The valve
filmoxide-hydrideofgrowth
thepreventtomixturegasdesign employs dual-flat-fac es togethe~ with a differensurface.
on the innerINTRODUCTION

Fig. 1 Assembly of the bending and quadrupole magnets
chambers with the bellows. Left side is electrode ofbeam position monitor.
Bellows
To absorb the mechanical tolerances, misalignment sof the components and the thermal expansion due to thebakeout procedure, a bellows between these aluminumvacuum chambers is required. An aluminum alloy seamlessbellows of racetrack shape is inserted between thealuminum chambers. Fig. 2. The bellows element isproduced by the hydraulic forming of a 0.35 mm thickseamless tube. In our design, the seamless tubes havethick wall near the ends, but are thin walled everwhere
else. The thickness of the corrugated part is reduced
to 0.35 mm while the welding edge parts are thickness 4mm. This contributes to both getting sound welds andbetter elastic performance of the bellows.

Fig. 2 Racetrack type, aluminum alloy(3004) seamlessbellows with rf insert(Be-Cu ).
tially pumped housing. The aperture of the gate valve
has the same recetrack cross section as the vacuum chamberof arc section. When the valve opens, the bellows assembly closes on the aperture of the gate valve to assuresmooth flow of the wall current. Fig. 6.
DC separators
16 DC separators are installed at both sides of thefour collision points. These are 2 types of the separator:
maximum operating voltage, +130 kV(Type 1) and +112 kV(Type 2), electrode size, 3500 mm long(Type 1) and 3300mm long(Type 2), 145 mm wide(Type 1 and 2). The chamberis 4010 mm long and 300 mm in inner diameter for both239

separators. A high voltage terminal is designed so as tobe operated at maximum voltage, ~150 kV. TiN coating on
the electrodes can be used to reduce unstable discharge
due to high secondary electron emissions of aluminumoxides. It must be mentioned that the parasitic mode
losses from a bunched beam to a vacuum chamber is not
negligible in the storage rings. The estimated parasitic
mode loss in our case is on the order of 100 W for 30 GeV,
7 mA x 7 mA and the single bunch. For cooling of the electrodes, heat pipes will be applied to simplify the structure of the separators.
Fixed mask
For physics experiments, it is necessary to reducethe background noises caused by stray electron or positron
beam and X-ray emitted by Bremsstrahlung or by synchrotron
radiation in various magnets. For this purpose couple of
fixed masks should be set in long straight section. A
fixed mask is installed in each insertion quadrupole
magnets. The fixed mask consists of 100 mm long lead
block surrounding the tapered aluminum alloy chamber.

Fig. 3 Stright section chamber with beam
position monitor electrodes.

Beam intensity monitor(DCCT) is installed in the ceramicchamber. A scraper, a beam stopper and a beam screen
monitors utilize the straight motion driving mechanism.
The driving mechanism is made of aluminum alloy. The
dynamic bellows is also an aluminum alloy. The optical
window for the visible light of synchrotron radiationconsists of an aluminum alloy(3003) sleeve and a sapphiredisk. X-ray window is made of Be and Al foil. The Be
window is mounted on the aluminum alloy base flange. TheBe foil(l5 x 27 x 0.2 mm) is welded on the flange by electron beam. Al-window 0.08 mm in thickness is sealed witha Helicoflex gasket. Both of Be and Al-window are protectedby helium gas from the corrosion due to NOx.
JOININGThe beam channels, the gate valves, the ceramic chambers and the bellows are joined by a fully automatic DCSPTIG welder. Most of the joints are non-demountable. The
automatic welder consists of a guide rail with gear and amoving stage. The moving stage is driven by a computer
controlled servo motor. The welding torch, a filler wirefeeder and an arc voltage controller are mounted on themoving stage,Fig. 9, Fig. 10Fig. 4 Straight section chamber
for septum magnet.

Cooling and X-ray shield
Cooled aluminum alloy block(lO mm high, 50 mm long)
formed on the inside wall of the beam pipe protects thealuminum alloy bellows, gate valves and the ceramic chambers against intense and hard synchrotron radiation. All
beam pipes are covered with lead of 10 mm in thickness toshield strong X-ray radiation. Fig. 7.

For demountable joints The Conflat type seal has beendeveloped in which aluminum alloy flange coated with CrN
or TiC and aluminum gaskets are used. Al-flanges(2219-T87) and the gasket(l050-Hl8) are structually same as traditional Conflat types. The CrN or TiC treatment on theknife edge surface of the flange is performed for hardening.
Anodized aluminum alloy bolts(2024-T4), non-anodized nuts
(6061-T6) and hard-anodized washers(2017-T3) are used totighten the flange.

BEAM MONITOR
Four button type pickup electrodes to detect thebeam position are installed in the quadrupole magnetchamber. SMA type vacuum feedthroughs are used. The
feedthrough consists of ceramic-aluminum alloy seal using
vacuum brazing. The beam position monitor electrodes
mounted on the qoadrupole magnet chamber were fixed to thequadrupole magnet using the aluminum casting frame. Fig.8.

Fig. 6 Dual flat face seal with differential pumping
type gate valve.

Fig. 5 Ceramic chamber with aluminum
bellows for kicker magnet.

PUMPS
The distributed sputter ion pump is installed .in thebending magnet chamber. Its anode consists of five layersof polished and perforated aluminum plate. The cathode ismade of special aluminum alloy(Al-Ti-Zr) rods 3 mm in diameter and is insulated from the vacuum chamber. Al-SHV
feedthrough is used as high voltage connectors of thedistributed ion pump. The feedthroughs are welded directly
to the bending magnet chamber by electron beam. Fig. 11Fig. 7.a Lead shield against X-ray radiation for the bending
magnet chamber.
7.b Lead shield for quadrupole magnetchamber.

240

Perforated and stacked anode cells for the standalone sputter ion pump have been used with the aim ofincreasing the conductance and active pumping surfaces.
The pump shell is made of the same extruded special
aluminum alloy(Al-Ti-Zr) as the cathode. 30 1/s ionpumps are used for the arc sections. Fig. 12. 125 1/s
and 250 1/s pumps are used for the straight section.
500 1/s ion pumps are used for the rf cavity.
The cartridge of non-evaporable getter(NEG) pumpis mounted on the Al-Conflat flange with an Al-BNC feedthrough. The module of the NEG type ST-707 pump isinstalled in the insertion quadrupole magnet chamber.

CONCLUSION
The present system satisfied conditions such as highperformance, high reliability, impedance matching,simplicity, low wasted space between magnets, small size,
low residual radioactivity and low cost.
ACKNOWLEDGMENTS
The author wishes to thank Director T. Nishikawa,Prof. T. Kamei, Y. Kimura, G. Horikoshi for their encouragement.

ROUGHING PUMP
50 1/s and 300 1/s turbomolecular pumps are made ofaluminum alloys. The flange is Al-Conflat type and thebody is also aluminum alloy(6061-T6). Especially, 300
1/s pump has oil free magnetic bearing.

Fig. 8 Beam position monitor mounted
on the quadrupole magnet chamber.

Fig. 9Fully automatic welder

All-aluminum alloy right angle valves were developed
using the sealing principle of the Helicoflex gasket.
For semi-automatic operation, a right angle valve isequipped with a closing mechanism, which consists of a
air motor. This ICF-114 type valve is useful as a safetyvalve for 50 1/s turbomolecular pumps in case of an
unexpected power outage. Fig. 13.
300 1/s magnetic bearing type turbomolecular pumpwith the manual right angle valve ICF-152 type utilizes
the automatic magnetic valve with the elastomer seal in
the back of the turbomolecular pump. This is safetysystem for an unexpected power outage.
A seamless cross piece, a T-piece and a 90° elbow
have been made of aluminum alloy(6063-T6) using a bulging
method. Al-Conflat flanges are welded to these pieces.

Fig. 11 Al-distributed sputter ion pumpis housed in the bending magnet vacuum
chamber. Left side is the pumping port.

Fig. 10 Layout of the magnets and thevacuum chambers drawn by CAD system.

1. H. Ishimaru et al., IEEE Trans. Vol. NS-28, No. 3,June, 1981, 3320
2. H. Ishimaru et al., Journal of Vacuum Science & Techno!.
A2, April-June, 1984, 1172
3. H. Ishimaru et al., Proceedings of 8th symposium on ion
source and ion assisted techno!., June, Tokyo, 1984, 185

Fig. 12 Stand alone 30 1/s ion pumpfor the arc section.

241

Fig. 13 50 1/s Al-turbomolecul arpump for the arc section.