TiN Coating and Baking of Beam Pipes

Magnetron discharge sputtering for TiN coating

The 19th KEKB Accelerator Review Committee
March 3, 2014
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+) : Baking & TiN coating at the laboratory
For Damping Ring : TiN coating at the laboratory
For all beam pipes : assembling work (NEG pump , BPM electrode)• How many beam pipes should be processed?
– For HER (e‐) : 180
– For LER (e+) : 1000 (of which  25 have electron clearing electrodes and TiNcoating is unnecessary. )– Damping Ring : 100

• Pre‐installation work (coating and baking) started on April 2012.
– “Pre‐installation work” means:
Bringing beam pipes to KEKB Oho Lab. from storage area ‐> Coating (3days) ‐> Baking (3days) ‐>returning the beam pipes to storage area

– Large‐scale works by 10 workers started on September 2012.
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the 19th KEKB Accelerator Review Committee2Flow chart ofpre‐installation work

Storage areaBringing beam pipes to KEKB
Oho Lab. from storage area
KEKB Oho Lab.

Visual check on the beam pipe
LER beam pipe
without electrodeDR beam pipe

TiN Coating

HER beam pipe
LER beam pipewith electrode

Assembling(NEG pump & BPM electrode)

KEKB Oho Lab.

3‐go‐kan Bldg.
(You are here.)

KEK Tsukuba Campus
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BakingDR beam pipe

Returning the beam pipes to storage area

the 19th KEKB Accelerator Review Committee

3Introduction 2• What we did after last KEKB Review are– Setting up horizontal coating facility with 2 equipment systems for bent beampipes.
– Coating and baking of 430 beam pipes for LER and HER, of which 111 beam
pipes were bent pipe and coated by the new horizontal facility.
• Pre‐installation works of 925 beam pipes were finished in total so far.
• More 450 beam pipes (LER and HER : 350, Damping Ring : 100) must be coated and baked by
the end of this year.

– Modifying the horizontal coating facility for damping ring beam pipes. (inprogress now)

• Topics discussed in this talk are– Baking & TiN coating facility (review)– Status report on baking and coating works– Working ScheduleNow
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4Layout of Oho laboratory 1
Baking equipment : 2 long type (5 m) and 2 short type (3 m)
Vertical TiN coating facility with 4 equipment systems for straight beam pipes
Horizontal coating facility with 2 equipment systems for bent beam pipes

•••

16m

4.5mm

Clean room
coating facility(vertical)

6.5 m

stairway

Baking equipment (short type)

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

Baking equipment (long type)stairway

Coating facility(horizontal)

Oho experimental
deck (top view)

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the 19th KEKB Accelerator Review Committee5Layout of Oho laboratory 2• View from different place.

Clean room

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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 Committee

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Baking 2 : Baking conditions•

Baking conditions– Temperature : 150 C (120 C for beam pipes with electrodes)– Baking period : 26 hours• Temperature of the beam pipes in the oven became 150 C within
a several hours.

– 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 : Baking output••

Baking work started on April
2012.
Total output by last month(2014/2/28) is 925.
Now we are here.
(waiting for new beam pipes.)•More 350 beam pipes must
be baked by the end ofNovember at the latest.
– Last year 367 beam pipes werebaked in 7 months (from April toOctober).
– Baking work will restart fromApril.

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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.
– Mass pattern after baking is not monitored. (Though 2 of 4 baking equipment systems
have RGAs, we don’t use them.)<1122334455667788991010 <[x10‐8 Pa]
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10TiN coating 1 : Coting method•

For SuperKEKB LER and DR, it is an important issue tomitigate the electron cloud instability.
– In order to reduce the electron cloud, inner surfaces ofalmost all LER beam pipes are coated with TiN (except
beam pipes with clearing electrodes).
– TiN coating tests had been performed and the coating
method 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.
– 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 to
decide 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 mTGauge

Pumping System

stand
MassTest
Spectrometer

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TiN coating 2 : Facility (vertical)• Straight beam pipes are coated by vertical facility with 4 equipment
systems..
–––––––

Ti cathode is hung from the top of the pipe.
Beam pipe with a length up to 5.5 m can be coated.
Short beam pipes and dummy pipes are connected to make total
length 6 m.
Two lines of the beam pipes can be mounted side‐by‐side in oneequipment.
Combination of hot‐air oven and circulators are adopted for pre‐baking.
It is not available for bent beam pipes.
Large‐scale work started on September 2012.
6 m

Dummy pipe forlength tuning
Beam pipes

Two lines of beam pipes

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Vertical coating facility

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TiN coating 3 : Facility (horizontal)• Bent beam pipes are coated by horizontal facility with 2 equipment
systems.
– Basically, horizontal equipment has the same structure with vertical equipment.
– Beam pipes lie down in the solenoid coils.
– Ti cathode is set horizontally on the center axis of beam pipe by the ceramics
supports with wheels.
– Large‐scale work started on April 2013.

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TiN coating 4 : 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 5 : 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)
Vertical typePartial pressure during discharge (just upstream of pumping unit)
1x100

Ar

1x10‐1N2

1x10‐2

Partial Pressure [Pa]•••Ti cathode rod

1x10‐3
1x10‐4

H2
Ti coating

Horizontal type

TiN coating

1x10‐5
1x10‐6
1x10‐7
1x10‐8Time
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TiN coating 6 : Coating 2

Electron microscopic image of TiN coating

Beam pipe (bent type) was successfully coated.
Though the color of the ceramic support was changed,
insulation breakdown did not occurred.

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TiN coating 7 : 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)
By S. Terui

Al samples before coating

By S. Terui

2.2

1.3
1.1

TiN coated samples

0.9

0.72
0.5

Al flat

Al groove

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TiN coating 8 : Modification for DR 1••

Coating of beam pipes for DR are done by the horizontal facility.
New Ti cathode plate with the same curvature as the beam pipe is required.

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TiN coating 9 : Modification for DR 2••

Modification for DR is nearly done.
Coating work will start soon.
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TiN coating 10 : Coating output••

Coating work started on July2012.
Total output by last month(2014/2/28) is 805.

Damping ring (100)
LER (180)•More 280 beam pipes(LER:180, DR:100) must be
coated by the end of this year.
– Last year 345 beam pipes werecoated in 7 months (from April toOctober).
– LER : From April to October at
the latest.
– DR : March, November andDecember.

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Now we are here.
(modifying the horizontal facility
and waiting for new beam pipes.)the 19th KEKB Accelerator Review Committee

20Summary•

Pre‐installation works (coating and baking) started on April 2012.
– Large‐scale works by 10 workers started on September 2012.
– Coating of bent beam pipes started on last April by the horizontal coating facility– Pre‐installation works of 925 beam pipes were finished in total, of which 111 beam pipes werebent pipe and coated by the horizontal facility.

•Pre‐installation work has been performed well so far without any serious problems.
– Though many connection flanges (MO flange) required treatment for scratches on the vacuum
sealing surfaces after coating, this problem was solved by burnishing sealing surfaces with hand.
– Pre‐installation work is almost on schedule so far.

•Modifying the horizontal coating facility for damping ring beam pipes is in progress now.
– Coating work will start soon.

•By the end of this year, 450 beam pipes must be baked and coated.
– LER and HER (350): From April to November at the latest.
– Damping Ring (100): March, November and December.
– “450 beam pipes” seem to be an achievable goal.

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