TiN Coating and Baking of Beam Pipes

KEKB Oho Lab. (2013.2.27)
The 18th KEKB Accelerator Review Committee
March 4, 2013
Kyo Shibata (on behalf of KEKB Vacuum Group)Introduction 1• What should we do before the installation of new beam pipes?
– For HER (e‐) : Baking at the laboratory(not in‐situ)– For LER (e+) and Damping Ring : Baking & TiN coating at the laboratory• How many beam pipes should be processed?
– For HER (e‐) : 180
– For LER (e+) : 1000 (of which  25 have electron clearing electrodes andTiN coating is unnecessary. )– For Damping Ring : 100

• Pre‐installation works (coating and baking) started on last April.
– Pre‐installation work means:
Bringing beam pipes to KEKB Oho Lab. from storage area ‐> Coating (only for LER, 3days) ‐>Baking (3days) ‐> returning the beam pipes to storage area

– Large‐scale works by 10 workers with 4 coating equipments and 4 baking
equipments started on last September.
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Storage area

Flow chart ofpre‐installation work
Bringing beam pipes to KEKB
Oho Lab. from storage area
Visual check on the beam pipe
LER beam pipe
without electrode

KEKB Oho Lab.

HER beam pipe

TiN Coating

LER beam pipewith electrode

Assembling(NEG pump & BPM electrode)

KEKB Oho Lab.
3‐go‐kan Bldg.
(You are here.)
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BakingReturning the beam pipes to storage area
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3Introduction 2• What we did after last KEKB Review are– Setting up 2 more baking equipments and 4 coating equipments (vertical).
– Large‐scale work in this facility. (This will continue this year. )– Setting up 3 horizontal coating equipments for bent beam pipes. (in progress now)

• Topics discussed in this talk are– Baking & TiN coating facility, Evaluation of TiN coating, Status report on baking andcoating works and Future plan.
– Working Schedule

Last year
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Now4

Layout of Oho laboratory 1
4 baking equipments : 2 long type (5 m) and 2 short type (3 m)
5 vertical TiN coating equipments (for straight beam pipes. one of them is back up.)
3 horizontal TiN coating equipments (for bent pipes. In preparation now. )

••
•

16m
Coating equipment (horizontal type)Coating equipment (horizontal type)4.5mm

Clean room
Coating equipments(vertical type)

6.5 m

stairway

Baking equipment (short type)

Baking equipment (long type)
Baking equipment (short type)16m

Baking equipment (long type)stairway

Coating equipment (horizontal type)

Oho experimental
deck (top view)

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the 18th KEKB Accelerator Review Committee5Layout of Oho laboratory 2• View from different place.

Clean room

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6Baking 1 : Equipment• Hot‐air heating method was adopted.
– Two beam pipes are mounted up and down in one hot‐air oven.
– Hot‐air oven consists of movable insulated walls and insulated frame.
– Hot air is circulated in the hot‐air oven.
– Each pipe is evacuated by a turbo‐molecular pump (0.3 m3/sec) during the baking.
Movable walls

Now baking
Beam pipe(double decker)

Pumpingunit

Hot‐air circulator(7.5 kW)

Short type2013/3/4

Long typethe 18th KEKB Accelerator Review Committee7Baking 2 : Baking conditions•

Baking conditions– Temperature : 150 C (120 C for beam pipes with electrodes)– Baking period : 26 hours• It was confirmed that the temperature of the beam pipes in theoven became 150 C within a several hours if the temperature
setting of the hot‐air circulator was 175 C.

– Targeted pressure after baking : < 10‐7 Pa– NEG pump is activated at the same time.

•Before baking– TiN coating (if necessary)– Installation of NEG pumps and BPM electrodes at Oho cleanroom.

•Clean room

After baking– Filling with dry nitrogen up to atmospheric pressure.
– Isolating the beam pipe and putting a blank flange on the beampipe.
– Keeping the beam pipe in the storage area until the installation.
Storage area (Oho lab.)
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Baking 3 : Rate of baking output• Baking work started on last April.
– Baking work started on small scale with 2 baking equipments on last April.
– On last September large‐scale works with 4 baking equipments started.

• Total output by last month (2013/2/28) is 481.
– Averaged daily output : 0.8 (small‐scale), 2.0 (full‐scale), 1.4 (total)– Averaged weekly output : 5.5 (small‐scale), 13.9 (full‐scale), 10.0 (total)

Small‐scale work

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Large‐scale work

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9Baking 4 : Achieved pressure after baking•

For almost all beam pipes, achieved pressures after baking are below 1×10‐7 Pa.
– If achieved pressure is higher than 1×10‐7 Pa, the beam pipe is baked again. (only 3 casesso far)
– Mass pattern after baking is not monitored. (Although 2 of 4 baking equipment have RGAs,
we don’t use them.)<1122334455667788991010 <[x10‐8 Pa]
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TiN coating 1 : Coting method•

For SuperKEKB LER, it is an important issue to mitigate
the electron cloud instability.
– In order to reduce the electron cloud, inner surfaces ofalmost all LER beam pipes are coated with TiN (exceptbeam pipes with clearing electrodes).
– TiN coating tests had been performed and the coatingmethod was established.

•TiN coating is done by a DC magnetron sputtering of Ti
in Ar and N2 atmospheres.
– A Ti cathode rod (‐400 V) is set on the center axis of beampipe (hung from the top on in case of the vertical type).
– Gases are supplied into the beam pipes uniformly though
the Ti rod.
– Magnetic field (16 mT) is supplied by solenoid coils.
– Preliminary experiments were performed at a test stand todecide the coating parameters.
– Thickness of TiN coating : 200 nm (at least)– Straight beam pipes are coated by vertical type and bent
pipes are coated by horizontal type.
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Mass Flow Controller
Ar gas (2.0 Pa)
N2 gas (0.5 Pa)
Discharge
PowerSource
Solenoid CoilBeam pipe

Solenoid Coil’s
Power Source
Ti Cathode Rod(-400 V)

16 mT
Gauge

Pumping System

stand
MassTest
Spectrometer

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TiN coating 2 : Facility (vertical)• 5 vertical equipments for straight beam pipes were built last year.
– Large‐scale work started on last September with 4 verticalequipments.
– 1 equipment is backup and not available now.
– Beam pipe with a length up to 5.5 m can be coated.
– Short beam pipes and dummy pipes are connected to maketotal length 6 m.
– Two lines of the beam pipes can be mounted side‐by‐side in
one equipment.
– Combination of hot‐air oven and circulators are adopted forpre‐baking.
– It is not available for bent beam pipes.
6 mDummy pipe forlength tuning
Beam pipes

Two lines of beam pipes

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5 coating equipments (vertical)

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TiN coating 3 :View from bottom and middle floor
Viewing port and camera
at the bottom to observe
discharge

Solenoid coil

Hot air circulator

Pumping unit

Hot air circulator

Bottom floor

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Middle floor

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TiN coating 4 :View from top floor
Introduced gas line
Mass flow controllers

Control desk

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TiN coating 5 : Working process• Before coating (at Oho clean room)– Visual check on the beam pipe.
– Putting blank flanges on pumping ports and BPM ports.
– Connecting beam pipes and dummy pipes for length tuning. (if necessary)– Leakage test
– Installation of beam pipes on coating equipment.

• In coating equipment– Leakage test
– Pre‐baking (150 C, 24 hours)– TiN coating (Discharge duration : 80 min.)• After coating– Filling with dry nitrogen up to atmospheric pressure.
Leakage test before installation– Dismantling beam pipes– Installation of NEG pumps and BPM electrodes at Oho clean room.
– Baking

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TiN coating 6 : Installation of beam pipes 1

Hinge assembly to get beam pipe upright•Beam pipes are transported and installed on the coating equipment by crane.
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TiN coating 7 : Installation of beam pipes 2•

Beam pipes are transported and installed in the coating equipment by crane.

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TiN coating 8 : Installation of beam pipes 3
Introduced gas line

Ti cathodeInsulator

Bellows for
positioning of Ti
cathode rod• Ti cathode rod (6m) is also installed by crane.

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TiN coating 9 : Coating 1
Introduced gases : Ar (2.2 Pa), N2 (1.8 Pa)
Discharged current : 6.3 A
Required time : 5 min (Ti coating for base of TiN) + 75 min (TiN coating)Partial pressure during discharge (just upstream of pumping unit)
1x100

N2

1x10‐2
1x10‐3
1x10‐4

Ti cathode rod

Ar

1x10‐1

Partial Pressure [Pa]•••H2
Ti coating

TiN coating

1x10‐5
1x10‐6

View from viewportat the bottom

1x10‐7
1x10‐8Time
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TiN coating 10 : Coating 2

Electron microscopic image of TiN coating

Cu beam pipe coated with TiN

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TiN coating 11 : Performance evaluation• SEY of Al samples coated with TiN at this facility were measured.
– It was confirmed that SEY of TiN coating drops to below 0.8 after electron
irradiation (incident electron energy : 250 eV)– It was also confirmed that the cylindrical cathode rod is available for grooved
surface adopted in bent pipes.
By S. Terui

Al samples before coating

By S. Terui

2.2

1.3
1.1

TiN coated samples

0.90.72
0.5

Al flat

Al groove
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TiN coating 12 : Rate of coating output• Coating work started on last July.
– Coating work started on small scale with 1 coating equipment on last July.
– On last September large‐scale works with 4 coating equipments started.

• Total output by last month (2013/2/28) is 411.
– Averaged daily output : 1.0(small‐scale), 1.9 (full‐scale), 1.7 (total)– Averaged weekly output : 6.9 (small‐scale), 13.6 (full‐scale), 11.8 (total)Small‐scale work

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Large‐scale work

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TiN coating 13 : Horizontal type 1• Horizontal coating equipments for bent beam pipes are inpreparation now.

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TiN coating 14 : Horizontal type 2• Discharge test will be done this month• Large‐scale work with 2 equipment will start on April.

Installation test of Ti cathode rod in bent pipe

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the 18th KEKB Accelerator Review Committee24Troubles•

We had some troubles especially in the early stage.
– Deformation (1 Cu pipe) and cracks (3 Al pipes) of pipes at welding lines.
•••

Caused by stress mainly added during crane works.
Change in our assembly and handling processes to decrease stress.
Damaged beam pipes will be repaired.

– Vacuum leak at a welding line between connection flange and pipe•

Repaired by extra welding– Interruption of baking due to shutdown of pumps cased by earthquake
or electrical outage.
•Returning to the starting point of baking.

Crack at welding line

– Melting of NEG pump (GP50) during activation•

Change in power feeding method.

– Abnormal discharge during TiN coating.
••

Caused by insulation failure.
Removal of coating from insulator.

– Difficulty reducing residual H2O in coating equipment .
••Removal of dust on the bottom of coating equipment.

We have a lot less trouble recently.
– MO flange (Al) has the quality to last long and we had no problem with
it after coating and baking so far.

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Melted NEG pump25

Future plan•••Apr. 2013  Dec. 2013 : 390 beam pipes for LER and HERJan. 2014  Mar. 2014 : 80 beam pipes for Damping ring
April 2014  Dec. 2014 : 250 beam pipes for LER, HER and Damping ring

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26Summary• Pre‐installation works (coating and baking) started on last April.
– Large‐scale works by 10 workers with 4 vertical coating equipments and 4baking equipments started on last September.
– So far 411 beam pipes were coated and 481 beam pipes were baked.
– Though we had some troubles at the early stage, we have a lot less trouble
recently and we are on schedule.

• Horizontal coating facility will be operated on large scale from nextmonth.
– Coating test will be performed this month.

• During next fiscal year (April 2013 ‐ March 2014), 470 beam pipes willbe treated.

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