Vacuum Components R&D
for High Current Machine
Y.Suetsugu

KEKB Vacuum GroupContents
1. Beam Duct with Ante-chambers
2. Bellows Chamber and Gate Valve
3. Vacuum Flange
4. Movable Masks (preliminary)
5. Summary
2006/3/21

2006 KEKB Review

11. Beam Duct with Ante-chambers! Features

Beam duct with antechamber! Low SR power density atside wall
! Little photoelectrons in beamchannel! Low impedance[NEG Strip]

BeamSR! R&D points[SR Channel][Beam Channel]! Trial Manufacturing! Use Copper! Establish fabrication methods! Get base of cost estimation! Experimental demonstrationof photoelectron reduction
2006/3/21

2006 KEKB Review21. Beam Duct with Ante-chambers! Beam duct with one antechamber (2003-2004)! Model: for arc section! OFC(t6), w159, h94, L5.4 m

Beam duct with ante-chamber! Fabrication methods:! Forming (from plates)! Cold drawing! Both methods were possible.
! Test chambers were installed

into LER arc (2003).

! No serious problem was found up! " #$

to now.
! At the beginning, pressure bursts
were observed at (may be)transverse connection.
! To be cared in practical cases
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2006 KEKB Review

31. Beam Duct with Ante-chambers! Electron number in the beam channel (2003)! Measured by an electron

3.77 buckets spacing

Circular duct

Duct withante-chamber

Measurement limit

2006/3/21[Log Scale]monitor at the bottom ofduct (Bias = -30V)! The reduction was byorders at low current(Ib " 100mA).
! The reduction was byfactors at high current(Ib #1000 mA).
!Multipactoring becomes
important at highercurrent.

2006 KEKB Review

41. Beam Duct with Ante-chambers! Beam duct with two antechambers (2005)! Model: for wiggler section! OFC(t6), w224, h94, L4.7 m! Fabrication methods:! Forming (from plates)! Manufacturing was successful.

Forming! Degree of accuracy should be

improved in future

Inside view
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2006 KEKB Review

Final check5

1. Beam Duct with Ante-chambers! Beam test (2005)! Test duct was installed intoPhotons

Normalized here
Electroncurrent(at low beam current)

LER wiggler section.
! No problem was found up to1.7 A stored current.
! No pressure burst wasfound.
! Electron density in thebeam channel was alsomeasured.
! Reduction of photoelectrons

were confirmed again.

2006/3/21

2006 KEKB Review

Ante-chamber

Circular61. Beam Duct with Ante-chambers! Next step
! Reduction of secondary electrons in the beam channel.
! Study on surfaces with a low SEY is undergoing in parallel.

! Further studies for more practical cases! Combination with a coating with a low SEY to suppress electron

multipactoring.
! Bending for arc section.
! Manufacturing of beam duct with BPM for Q or SX magnet.

2006/3/21

2006 KEKB Review

72. Bellows Chamber and Gate Valve! Comb-type RF-shieldVer. 0! Has been studied from 2003

! Features! High thermal strength! Low impedance

Teeth! Effective RF shielding! Applicable to any cross section! R&D points! Experimental demonstration! Trial manufacturing

Back shield! Cost reduction

Shield finger! Simplification
2006/3/21

2006 KEKB Review82. Bellows Chamber and Gate Valve! Ver.0 (2003)! With back shield and shield finger! Trial model (!94) was installed

into LER (2003)! Temperature of bellows
decreased to 1/6 ofconventional one.
! Temperature of teeth was
about 50°C at 1.5 A.
! No problem was found up to1.7 A.
! Applied to bellows
for movable masks(2004).
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2006 KEKB Review

92. Bellows Chamber and Gate Valve! Ver.1 (2004)! Without back shield to simplify

the structure! Test model was installed intoLER (2004).
! Temperature of bellows wasalmost same as theconventional one.
! Pressure burst (may be dueto arcing) was observed
during operation in 2005.
! Will be removed andinvestigated during this
shutdown (2006).
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2006 KEKB Review

Pressure burst

PIb102. Bellows Chamber and Gate Valve! Ver.2 (2004)

Back shield! Without shield finger to simplify

the structure! Test model was installed into

HER (150x50) and LER (!94)(2005)! Temperature of bellows was
about 1/3~1/4 of conventionalone.

Temperature of bellows
Finger! RF shielding is still effective.
! Structure is much simplified.

! Temperature of teeth was 90°

C at 1.7 A.
! Applicable to gate valve.

! No abrasion between teeth
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2006 KEKB Review

Ver.2Ver.011

2. Bellows Chamber and Gate Valve! Application of Ver.2 to antechamber-type bellows! Manufactured at BINP (2005)! Copper cooling channel! Improve cooling of teeth! Two bellows chamber wereinstalled into LER wiggler (2005).
! No problem was found up to 1.7 A.

2006/3/21

2006 KEKB Review

122. Bellows Chamber and Gate Valve! Gate valve with Ver.2 shield! Manufactured by VAT Co.

(collaborative project)! Circular type was installed intoLER (2005)! Temperature of body was
about 1/3~1/6 of conventionalone.
! No problem was found up to1.7 A

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2006 KEKB Review

Temperature of body13

2. Bellows Chamber and Gate Valve! Next step
! Understand the reason of failureof Ver.1 shield.
! Inside check! It was OK in calculation. Why?

! Expand application of Ver.2

shield to bellows chambers andgate valves.
! Replace with broken bellows

chamber in KEKB.
! Racetrack gate valve with Ver.2
shield will be installed in KEKB thisspring (2006), and the performance
will be checked.
Inside view of racetrack gate valve
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2006 KEKB Review

143. Vacuum Flange! MO (Matsumoto-Ohtsuka) type flange! Has been studied since 2003

! Features! Seal a vacuum at only the innersurface! Vacuum seal doubles as RFbridge! No gap and step at the inner surface! Can follow the complicated crosssection! R&D points! Experimental demonstration
for non-uniform cross section! Beam test
Rectangular model (for waveguide)
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2006 KEKB Review15

3. Vacuum Flange! Bench test (2003-2004)

Trial models (only flanges)! Using blank flanges

SS! Vacuum sealing was

possible with a reasonable
fastening force.
! Stress of bolts is well below
the tensile strength.
! Baking up to 250°C, twistup to 5 mrad were OK.
! Promising results wereobtained.

Cu

Leak rate

SS flange
Cu gasket
2006/3/21

Inside view
2006 KEKB Review16

3. Vacuum Flange! Application to bellows chamber and ducts (2005)! MO-flange was applied to beam duct with ante-chambers

and their bellows chambers, and installed into LER.
! No problem was found up to 1.7 A.

! Temperature of bellows was almost same to conventional ones(circular). ~30 °C .
SS flange

Bellows chamber

Cu gasket

MO-type flange for beam duct withantechambers for wiggler section
2006/3/21

MO-type flange for bellows chamber

2006 KEKB Review17

3. Vacuum Flange! Next step
! Need further assessment ofperformance in real machine.
! Application of copper-alloy flange

was also tested, and good results
were obtained (2005).
! Continue further study.

Copper-alloy MO-type flange(courtesy of K. Sennyu, MHI)

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2006 KEKB Review

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4. Movable Mask
! Stealth type
! Has been studied since 2003

Ver.4 at present! Features! Ceramics support! Little interference with beam

! Carbon headHead (C)! Little damage by beam

! With HOM absorber (SiC)

SiC! R&D points (still preliminary)! Trapped mode

SiC! Heating of head
! Charge up

Beam! Experimental demonstration
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2006 KEKB Review

Support (ceramics)
Beam duct19

4. Movable Mask
! Trapped modes

$94

L300
SiC 2 x L45-90 x 45°! S11 were calculated.

! Two modes are trapped underTE11 cut off (1.87GHz @ $94)
Metal Support

Head 8 x 7 x 90
Support (%r=4), 6 x 4 x 30

Ceramics Support
S11

Mode 2(~0.7 GHz)
Mode 1(~1.4GHz)
0.5 GHz
2006/3/21

1 GHzTE111(~1.8GHz)

1.5 GHz

2 GHz

Mode 1(~1.4GHz)
0.5 GHz2006 KEKB Review

1 GHz

TE111
(~1.8GHz)

1.5 GHz

2 GHz20

4. Movable Mask
! Mode 2! Mode 1! f ~0.68 GHz! f ~ 1.38 GHz! Current flows back andforth along head

! Current flows back andforth along support.
! The mode that troubled
Ver.1~ 3 masks.

HHII

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2006 KEKB Review21

4. Movable Mask
! Mode 1 (f~1.38 GHz)
! Little dependence on the conductivity of support.
! For metal or ceramics support, Rs=100~10&, Q~1000! With SiC 2 x 45° x 45mm

! Not problem for CBI! Mode 2 (f~0.68 GHz)
! Rs (should) depend on the conductivity of support.
! For metal support, Rs~100k&, Q~1000 (even with SiC)
! Big problem for CBI, if metal support! To achieve a growth rate less than

30 s-1 for SKEKB,
Rs should be less than ~500 &.
! How much is the tolerable
conductivity? - not obtained yet.
2006/3/21

2006 KEKB Review! Required '-1 for SKEKB

Damping time = 30 msec(=2.7E-4, fs=3.1E3, 9.4 A,5120 bunches! # of mask=16!
!

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4. Movable Mask
! Heating of head
! If only radiation is considered, temperature ~ 800° C for

an input power of ~100 W.

! Emissivity ~ 0.5 for rough (dark) surface! Joule loss: ~50W (10A, Cu head, 10mm form beam)! Trapped mode: ??

! Need Rs!

! Charge up of head
! Metal coating (ex.Ti) with 0.1~1µm thick on the support isconsidered at present.
! Otherwise, TiN coating, or any paint with large
resistivity, as used in DAFNE.
! Coating method depends on the required conductivity.
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2006 KEKB Review23

4. Movable Mask
! Cold model! Al pipe, L300 mm, $94 mm! Carbon head with relatively complicated structure wassuccessfully manufactured.
! BN support: possible, but coating was found to be difficult.
! Consider possibility of Al2O3 (%r ~ 8)

! Measurement of RF characteristics is planed.
Trial carbon head
SiC bars(replaceable)
BN support

2006/3/21

Inside view

Setup for Q measurement

2006 KEKB Review

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4. Movable Mask
! Ex. S12 Measurement! Al head (w8 x t7 x L90)
! Measure Q, fr, and Rs (How? )Metal Support (Al)Ceramics (BN) Support
S12Mode 2(~0.7 GHz)

0.5 GHz
2006/3/21

Mode 1(~1.4GHz)

Mode 1(~1.4GHz)

2 GHz

0.5 GHz2006 KEKB Review

2 GHz25

4. Movable Mask
! Next step
! Evaluate RF properties for a support with a thin finite-conductive layer.

! Calculation by simulation codes (Microwave Studio and Mafia) has

been tried, but not yet completed.
! Actually, the R&D stopped in this point.
! Just in the midst of a struggle.
! Check RF characteristics by a cold model.
! How control the conductivity of support? This is also a problem.

! Continue further study.
! Can we get any hint for clearing electrodes??

2006/3/21

2006 KEKB Review

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5. Summary! R&D of vacuum components are progressingsteadily.

Beam duct with ante-chambers! Bellows chamber and gate valves with comb-type RF shield (Ver.2)! MO-type vacuum flange! Stealth type movable mask!

! Beam duct with antechamber, comb-type RF-shielding and MO-type flange are close to practicaluse.
!

Apply to KEKB and accumulate practical experience.

! Further studies are required for stealth-type

movable mask.
!

RF characteristics for a support with a thin finite-conductive layer
is required at first.

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2006 KEKB Review

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