R&D Activities for ARES Upgrade
Tetsuo Abe
for KEKB-RF/ARES-cavity group

High Energy Accelerator Research Organization (KEK)＜Outline＞
1. R&D programs for SuperKEKB
2. L-band HOM-load test stand3. Input couplers with TiN coating
4. New copper electroplating for S-cav
5. Summary
KEKB Review@KEK2005.02.22

Accelerator Resonantly-coupled with Energy Storage
3-cavity system stabilized with the π/2-mode operationconsists ofz HOM-damped accelerating cavity (A-cav)
z Energy-storage cavity with TE013 (S-cav)z Coupling cavity(C-cav)
with a parasitic-mode damper

2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)1

Accelerator Resonantly-coupled with Energy Storage
3-cavity system stabilized with the π/2-mode operation

Top View

Input Coupler Port

consists ofz HOM-damped accelerating cavity (A-cav)
z Energy-storage cavity with TE013 (S-cav)z Coupling cavity(C-cav)
with a parasitic-mode damper

2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)2Upgrade Items toward
Measures against

 Larger detuningÆ Increase the energy ratio: Us/Ua = 9 → 15.
Æ Reported in the previous KEKB review
Æ Skipped this timeΔf π / 2 =Δf a
1 + Us / Ua Higher HOM powers
Æ HOM-load upgrade

 Higher input RF powers (400kW/cav → 800kW/cav)
Æ TiN coating on the coaxial lineÆ Coupler test stand upgraded for ~800kW(CW)
2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)3

R&D Programs 2004(JFY)[1] Construction of a new L-band HOM-load test standÆ Using 1.25GHz klystron (1.2MW, CW)Æ The 1st stage just finished[2] Input couplers with TiN coatingÆ Against multipactoring in the coaxial line
Æ TiN(Titanium Nitride) has low secondary-electron yields and is goodfor vacuum.
Æ Two couplers have been completed.
Æ Being tested in the upgraded coupler test stand up to 800kW.

[3] New highly-pure copper electroplating for S-cav
Æ The old facility has been retired.
Æ Reusing a facility being used for J-PARC.
2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)4

[1] L-band HOM Test Stand
ARES HOM-damped Structure

HOM

HOM

HOM

(Side view)

2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)5SiC Absorbers
 In the HOM Wave Guide (WG)z Direct water coolingzLimit: >26kW/cav (HPT) In the Grooved Beam Pipe (GBP)zIndirect water coolingÆ via the copper platezLimit: ~3.6kW/cav (HPT)Max. power which can be supplied by the old L-band klystron.
2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)6HOM Extrapolation for Super-KEKB LER(KEKB)(Super-KEKB)

Nb: 1224
 HOM in WG load (LER):
σz: 7mm26kW/cav (HPT)
Æ 80kW/cav (SuperKEKB)

4896 (full)3mmÆ Need HPTs over 26kW
Æ Increase # of absorbers /WG
Æ Enhanced water cooling HOM in GBP load (LER):
3.6kW/cav (HPT)Æ 20kW/cav (SuperKEKB)ÆNeed direct water cooling like in…
2 x GBP (Nb=1224, BL=7mm)
2 x GBP (Nb=4896, BL=4mm)
2 x GBP (Nb=4896, BL=3mm)
4 x HOM WG (Nb=1224, BL=7mm)
4 x HOM WG (Nb=4896, BL=4mm)
4 x HOM WG (Nb=4896 BL=3mm)

2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)7

Winged chamber loaded with SiC Absorbers(used in the movable-mask sections)Y. Suetsugu et al., “Development of Winged
HOM Damper for Movable Mask in KEKB”,
Proc. PAC2003.

Æ Can be a prototype.
Directly water-cooled SiC bullet

2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)8

New A-cav Design with Winged Chambers

Directly water-cooled SiC bullet

2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)9We cannot test HOM loads with high powers
for SuperKEKB.

More powerful klystron is needed
to upgrade the HOM loads.

2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)10

Construction of
New Test Stand for the HOM-load Upgrade
Reusing an L-band klystron, which is capable of 1.2
MW CW power ( freq. = 1.25 GHz).
Operating conditions (HV & cooling system etc.) aregoing to be regulated for our purpose.
The 1st stage of the construction has been justfinished.

2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)11

D01C/ARES HOM-load Test Stand
L-band klystron

Water dummy load

Output from the klystron(Taken on 2005.02.20)

2005.02.22 KEKB Review

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The 1st RF Power Comes!
2005.02.21

Output power
beyond the max. obtainedin the old L-band test stand(3.3kW)Æ Tuning to deliver more RF power up to 100 kW
2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)13[2] Input Couplers with TiN Coating
The problem is the multipactoring in the coaxial line.
Coupling Loop

Coaxial Line (WX77D)

2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)

Example of
the TV-camera snapshotsof the multipactoringin the coaxial line

14

Simulation Study Solving eq. of motion with theRunge-Kutta method
 Assuming the SEY of conditioned
copper Count number of collisions.

2005.02.22 KEKB Review

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On Which Side?
On the inner conductor

On the outer conductor

Almost single-side multipactoring on the outer conductor
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Coating Area

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Setup of the TiN Coating(DC Sputtering)z3E-4Pa before coatingzInjected gas: Ar and N2
zBeing used for TiN coating(10nm) of
RF Ceramic windows

Outer conductor

Ti electrode@MHI
2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)18

Studies on
Total gas pressure

Gas mixture ratio (Ar:N2)
Thickness meas.

~50nm

done by direct observation using SEM

set

TiN coating
Glass plate

Secondary electron yields

For the details, see the slides presented in the 6th Workshop on a Higher Luminosity B Factory:
http://belle.kek.jp/superb/workshop/2004/HL6/program.html .
2005.02.22 KEKB Review

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Two input couplers have been TiN-coatedwith the final condition.

(taken on 2004.11.10)

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After Coating

Before coating2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)21

Fabrication
Leak test

Tested in the upgrade coupler test stand2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)22

Old Setup of the Coupler Test Standz No RF output
ÆS-cav works as a dummy load.
ÆInput powers are limited: <400kW.
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R&D Activities for ARES Upgradeby T. Abe (KEK)23

Coupler Test Stand
Upgraded for Higher Power Capability: 400Æ800kW

Input coupler usedas output coupler

1M

W

Input coupler

S-cav

DL

To 1- MW Water Dummy Load2005.02.22 KEKB Review

From 1- MW CW Klystron

R&D Activities for ARES Upgradeby T. Abe (KEK)24

Another characteristic:
The coupling-loop angles of the input and output couplers
are set to be the same.

Æ No reflection (Γ~0.0)
r0Æ No Z-dependenceZ

The hardest ordeal
for couplers

2005.02.22 KEKB Review

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Power History

(β=3)

(β=1)

Routes of the old and upgraded test stands(Data taken in 2005.02.01-10 @D01A/ARES TS)

Any operating condition can be
simulated in the test stand bychanging the coupling-loop anglesof the input and output couplers!

To be compared with results on a coupler w/o TiN coating
To be tested in the D04C station? (“genuine” test stand?)2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)26

[3] New Copper Electroplating for S-cav
S-cav is made from Iron with copper electroplating.
 Present S-cav --- electroplating in a pyrophosphate bathz With brightener Æ little defect on the surface
z The facility has been retired.

 S-cav for SuperKEKB --- new electroplating in an acid sulfate bathaaaaaaaaaaaaaaaaaaaaaaaaperformed in the periodic reverse (PR) process
H. Ino, et. al, "Advanced copper lining for accelerator components",
Proc. of LAC2000, Monterey, CALIFORNIA, 1015 (2000)

z Without brightener Æ high purity, high electric conductivity (102%IACS),
but possible defects on the surface
z Using the facility being used for J-PARC
Ex. DTL tank2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)27

Difference between J-PARC and SuperKEKB¾ J-PARC casez Thickness:~1mm Æ Mechanical polishing(-0.5mm) Æ Electrolytic Polishing (EP)¾ SuperKEKB casez Thickness:~0.2mm

Æ Electrolytic Polishing (EP)Studies onzThickness (targets)
Ground(alkalinity): ~50µm
Main(acidity):~150µmElectrolytic Polishing: about -40µm
zLess defectzElectric performanceÆCheck Q0.
2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)28

Pillbox Test Cavity

Diameter: 451.2mm
Height: 260.0mm

Made from iron (SS400)(Before copper electroplating)(After copper electroplating)2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)29

Theoretical Calculationof Q0 (=Q0(cal))Cal Analytical solution of the electromagnetic field in the pillbox cavityjωµ0 mj'pπ z
J m ( mn r ) sin mθ sin
k2 rbdjωµ0 j 'mn
j 'mn
pπ z
Eθ = A 2
J 'm (r ) cos mθ sinkbbdEz = 0TEmnp modej'pπ z
1 pπ j 'mn
J 'm ( mn r ) cos mθ cos
k2 d b
b
d
j 'mn
pπ z
1 pπ mHθ = − A 2
Jm (r ) sin mθ cos
k d r
b
d
j 'mn
pπ z
H z = AJ m (r ) cos mθ sinbdHr = A Q0(m,n,p) = ωmnp

U
Pwall

U=

Pwall =

ε0jpπ z
1 pπ jmn
J 'm ( mn r ) cos mθ sin
k2 d bbdjmn
pπ z
1 pπ mEθ = A 2
Jm (r ) sin mθ sin
k d r
b
d
jmn
pπ z
Ez = AJ m (r ) cos mθ cosbdjωε 0 mjmn
pπ z
Hr = − A 2
Jm (r ) sin mθ cos
k rbdjωε 0 jmn
jmn
pπ z
Hθ = − A 2
J 'm (r ) cos mθ coskbbd
Hz = 0Er = − A

Er = A

TMmnp modeGGµ
dV | E |2 = 0 ∫ dV | H |2
cavity2 cavity

2 ∫

G 2
1 ωµ
|
|
dS
H
2 2σ ∫cavity

 Assumingz 100%IACS electric conductivity (=1/1.72E-8Ωm)
z flat surface (i.e. no defect)2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)

30

IACS
z International Annealed Copper Standard
z 100%IACS electric conductivity: 1/1.72E-8Ωm
z The electric conductivity of the highest-class oxygenfree copper: 102%IACS
Cf. Electroplating in an acid sulfate bath w/o brightener: 102%IACS

2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)312005.02.22 KEKB Review

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2005.02.22 KEKB Review

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After Trial and Error…

BarrelCopper Electroplating in an acid sulfate bath w/o brightener (PR process)EndcapFine!

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After Trial and Error…

BarrelCopper Electroplating in an acid sulfate bath w/o brightener (PR process)Electrolytic
Fine!

Endcappolishing2005.02.22 KEKB Review

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After Trial and Error…

BarrelCopper Electroplating in an acid sulfate bath w/o brightener (PR process)Electrolytic
Gorgeous!

Fine!

Endcappolishing2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)36

Thickness Measurement
ｼｱﾝ化銅メッキ＋硫酸銅メッキ膜厚Barrel before electrolytic polishing
280
260

Thickness[µm]
膜厚(μm)

240
220

1
3
5
7

200
180
160
140
120
250

240

230

220

210

200

190

180

170

160

150

140

130

120

110

100

90

80

70

60

50

40

30

20

10

100

上端面からの距離mm)
Distancefrom the edge [mm]2005.02.22 KEKB Review

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Setup of the Q0 Measurement

2005.02.22 KEKB Review

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Setup (close view)

Loop
couples with magnetic field.

Antennacouples with electric field.

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Results of the Q0 Measurements

Electroplating in a pyrophosphate bathwith brightener (applied to the present S-cav’s)(no temperature correction)

2005.02.22 KEKB Review

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Results of the Q0 Measurements
DC electric conductivity (102%IACS)

Frequency d epende
n ce com es from defe

cts on thesurface.

TM modesTE modesElectroplating in an acid sulfate bathwithout brightener
before electrolytic polishing(@20degC)

Electroplating in a pyrophosphate bathwith brightener (applied to the present S-cav’s)(no temperature correction)

2005.02.22 KEKB Review

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Results of the Q0 Measurements
DC electric conductivity (102%IACS)
Electroplating in an acid sulfate bathwithout brightener
after electrolytic polishing

No defect!

(@20degC)
Frequency d epende
n ce com es from defe

cts on thesurface.

TM modesTE modesElectroplating in an acid sulfate bathwithout brightener
before electrolytic polishing(@20degC)

Electroplating in the pyrophosphate bathwith brightener (applied to the present S-cav’s)(no temperature correction)

2005.02.22 KEKB Review

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Next Step: Vacuum TestzThe test cavity has been fabricated.
zThe electroplating is ongoing.
zA vacuum test will be done next month.
φ500mmBarrelEndcap2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)43

Summary ARES R&D programs are ongoing well.
 A new L-band test stand has been constructedÆ For the HOM-load upgrade.
Æ The 1st stage has been finished.
Æ To be tuned for supplying high powers.

 Input couplers with TiN coatingÆ Against multipactoring in the coaxial line.
Æ Two TiN-coated couplers have been completed.
Æ Being tested in the upgraded coupler test stand up to 800kW(CW).

 New highly-pure copper electroplating for S-cav
Æ On the slightly different condition from J-PARC.
Æ The electric performance is estimated to be excellent.
Æ A vacuum test to be done next month.
2005.02.22 KEKB Review

R&D Activities for ARES Upgradeby T. Abe (KEK)44