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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 1
CouplersDesign and Fabrication Issues of
High Power & Higher Order Modes Couplers for Superconducting Cavities
Shuichi Noguchi, KEK
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 2
ContentsDesign Issues of Input CouplerDesign Issues of HOM Coupler
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 3
RF Power Input Coupler
CavityCoupler
Power Source
WarmAir
ColdVacuum
RF Power
Ceramic Window
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 4
Coupler Design & Fabrication
Design Fabrication
RF GeometryCoaxial
Rectangular
Mechanical Material Cu Plated SUS
Thermal MethodTig Welding
Brazing, EBW
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 5
Design Issues of Input Coupler
Type ; Coaxial or Wave GuidePosition ; Cell or Beam PipeNumber of Windows ; Single or DoubleCooling ; Conduction, G-He, L-He, L-N2, WaterNumber of Couplers
FrequencyMaximum PowerOperation ModeHeat LoadCoupling Tune-ability
Requirements/ Specification
Choices
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 6
Best Choice for SCCoaxial Antenna Type Coupler on Beam Pipe is usually the Best Solution.Exception ;
Low β Cavity ; Coaxial Antenna on CavityHigh Frequency Cavity ; Wave Guide
CavityBeam Pipe
Coupler
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 7
Accelerator TRISTAN KEKB
SNS LEP FLASH CEBAF
Frequency 508MHz 805MHz 324MHz 1.3GHz 1.5GHzPower
RequirementCW
400kWPulse
400kW CW
100kWPulse
300kWCW
10kWCoupler Type Coaxial
Antenna Coaxial Antenna
Coaxial Antenna
Coaxial Antenna
Wave Guide
Window Type Size
Coaxial Disk
Coaxial Disk
Cylinder Cylinder Square
Ceramic Size φ180,t10 φ100,t9 φ150 φ40, φ60 60 x 120Used Coupler ~40 ~80 ~200 ~80 ~350
Major Couplers used
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 8
Coaxial Antenna Coupler
ExamplesComponentsCoupling
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 9
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 10
TTF-III
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 11
TTF-3 CouplerCoupler Support
CavityProcessing Stand
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Coaxial Disk Type Window Coupler
SNS KEK-JAEA
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STF-1
STF-2
KEK-ERL
TTF-V
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Bellows
STF-I & II Couplers
50Ω
Fixed
41Ω
Tune-able
Doorknob
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 15
5 k80k
CW Input Coupler for KEK-ERL
Water Cooled
Coaxial Ceramic Window
Extension to Outside of Cryostat
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 16
ERL Injector Cryomodule
e-
Vacuum VesselInput CouplerDouble Feed
Cavity3 x 2-cell
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 17
Components of Coaxial Antenna CouplerCoaxial Line (Cu Plated SUS)Window ( High Purity Al2O3 )Wave Guide to Coaxial TransformerDiagnostics
Vacuum, Arcing, Electron
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RF Design CriteriaMaximum Peak E ( Pulse High Power Application )
Loss ( CW Application )Reflection Multipacting
Fabrication, Assembly, Risk, etc.
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 19
Coaxial Waveguide ( TEM-Modes )
( ) ( )
Impedance sticCharacteri;ln2
A2,lnA
A1,A
0,0
,0,0
0
2
0
abZ
IVZ
eZ
daJIeabdrEV
erZ
Her
E
Hrr
Err
HE
i
zj
iS
zjb
a r
zj
i
zjr
r
r
π
πθ βπβ
βθ
β
θ
θ
==
====
==
=∂∂
=∂∂
==
−−
−−
∫∫
a b
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 20
Power Loss( )
ab
PZ
baZPR
ab
baZP
R
baZRbdHadHRP
ab
ZrdrdHEP
fi
fS
i
fS
iSbrarSloss
i
b
a rf
lnA
112
ln11
11A21
lnARe21
0
2
22
0
2
0
22
22
0
π
π
πθθ
πθ
π π
θθ
π
θ
=
⎟⎠⎞
⎜⎝⎛ +=⎟
⎠⎞
⎜⎝⎛ +=
⎟⎠⎞
⎜⎝⎛ +=⎥⎦
⎤⎢⎣⎡ +=
==
∫ ∫
∫ ∫
==
∗
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 21
Power Loss & E-Field Strength
4030 50 60 70Ω
0.1
0.2
0.3
1.7
1.5
1.3
Loss (Cu)W/kW.m
E FiledkV/MW.mm
Impedance
TTF-III
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WG
Coaxial Disk
Conical Capacitive Cylinder Cylinder at WG Transformer
RF Windows of Coaxial Coupler
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Coaxial Disk Window
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Ceramics Window
Al2 O3 ; 95 – 99 %ε
; ~9
Tan δ ; ∼0.0003 −
∼0.0001
MolybdenumTiN Coating on Vacuum Side
GoldBraze
Mo, Mn
( )1-mtan2 δλπ
=P
Ploss
Copper
Difference in thermal expansion coefficient is key.
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HFSS Simulation
WG Transformer
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S11 = -21.3 dB at 1.3GHz
S11 = -35. dB at 1.3GHz
Warm window and Doorknob
S11 = -26. dB at 1.3GHz
Part by Part
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Coupling / Tune-ability
b
beam
in QQPP
QQ11111;Coupling Optimum
000
+=⎟⎟⎠
⎞⎜⎜⎝
⎛+=
useful. bemay ability -Tune Coupling Current Beamon depends,;0 binbeam QQPP =>>
controll. RFbetter for desireble is107≤inQ
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 28
Double Couplers
( )zktjgg eEP
−∝ ω11 ;r )(
22 ;Ψ++∝ zktjgg eEP
ωr
1111 ; troutout EEEPrrr
+=
Coupler #1 ; β1 Coupler #2 ; β2
2222 ; troutout EEEPrrr
+=
Optimum Coupling ; 021 == outout PP
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Superposition
Pg1
Pr1
Pt2 Pt1Pg2
Pr2
Pg1
Pout1
Pg2
Pout2
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At Resonance( )
21
1
1
01
21
21
1
2
1
2
21
12
1
1
21
12
1
1
1
1
12
12
112
11
βββ
ββββ
ββββ
ββββ
++=
++==
+++
=++−+
==
gg
t
g
t
g
in
g
r
g
r
PP
EE
PP
PP
EE
PP
( )
( ) ( )Φ++++
−
==
=='
2211
1111
zktjtt
zktjrr
tjaccacc
zktjgg
eEEeEE
eEEeEEωφω
ωω
rr
rr
( ) ( )1eUndercoupl;1Overcouple;0 11 = ∗∗ βπφβφ
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 31
Optimum Coupling 021 == outout PP
( )[ ]Φ−Ψ−++=+∝ φcos2 1121212
111 trtrtrout EEEEEEPrr
Φ=Ψ= and If πφ ( )2111 trout EEP −∝
21If gg PP =2
21
21211 1
21⎟⎟⎠
⎞⎜⎜⎝
⎛
++−+−
∝ββ
ββββoutP
2
21
21212 1
21⎟⎟⎠
⎞⎜⎜⎝
⎛
++−−+
∝ββ
ββββoutP
21
21 == ββ
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Processing ( Acceptance Test )
Make them CleanKeep them CleanCareful Processing with DiagnosticsArc Detector, Electron Monitor, Vacuum
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Processing of TTF-V Couplers at KEKStep 1 ; Target for XFEL
1.0 MW / 400 μs, 500 kW / 1.3 ms, 5 Hz
20 μs5 Hz
20 μs1 Hz
20 μs5 Hz
50 μs
100 μs200 μs400 μs
0.8 ms1.3 ms1.5 ms
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TTF-V Couplers at KEKStep 2 ; Target for ILC 2.0 MW / 400 μs, 1.0 MW / 1.5 ms, 5 Hz
400 μs, 5 Hz
100 μs200 μs
10~50 μs,5 Hz10 μs,1Hz20 μs,5Hz
100 μs200 μs
400 μs
50 μs20 μs
2.0 MW
400 μs
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HOM CouplerDevice to lower Q-Values of HOM’sOutput Coupler for HOM’s excited by BeamNeed Filter for the Operating ModeSo Many HOM Couplers have been designed and used.Beam Pipe Absorber is an Alternative.
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 36
Design Issues of HOM Coupler
Type ; Coaxial or Wave GuidePosition ; Cell or Beam PipeWelded or FlangeNumber of CouplersCoolingPosition of Loads
FrequencyDumpingMaximum PowerOperation ModeHeat Load
Requirements/ Specification
Choice
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 37
Best Choice
Coaxial Loop Type Coupler on Beam Pipe is the Best Solution. ( TESLA-like )Being used up to 3.9GHz Cavity.
Cavity
Beam Pipe
Nb HOM
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HOM couplers and Beam Line Absorbers HOMThe TESLA –like HOM couplers are nowadays
designed in frequency range: 0.8-3.9 GHz
Cs Cf
Co
L1 L2 Ro
x1, z1 x2, z1
J. Sekutowitz DESY
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High-pass Filter ( + Notch Filter )
-20
-15
-10
-5
0
5
1 1.5 2 2.5 3
high pass filter transmission
S21[dB] offset=0,no stubS21[dB] offset=10,no stubS21[dB] offset=10,1stubS21[dB] offset=10,2stub,40mmS21[dB] offset=0,2stub,40mm
S21[dB]
freq[GHz]
1.3GHz
-30
-25
-20
-15
-10
-5
0
5
1 1.5 2 2.5 3
high pass filter transmission2stub, S=50mm
S21[dB] offset=0,2stub,50mmS21[dB] offset=2,2stub,50mmS21[dB] offset=4,2stub,50mmS21[dB] offset=6,2stub,50mmS21[dB] offset=8,2stub,50mmS21[dB] offset=10,2stub,50mmS21[dB] offset=-2,2stub,50mm
S21[d
B]
freq[GHz]
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HFSS Simulation HOM Coupler
H Field
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HOM couplers and Beam Line Absorbers HOMWaveguide HOM couplersC
EB
AF/
Cor
nell
1.5
GH
z HOM ports
HOM loadsDesign (1982) works at present in
CEBAF both linacs with
Ibeam ~ 80µAx4 @ Eacc 7 MV/m
HOM power is very low. It can be dissipated inside cryomodule.
Design proposed by R. Rimmer (JLab)750 MHz for 1A class ERLs
PAC2005
Design proposed by G. Wu (JLab)1500 MHz for 100 mA class ERLs
LINAC2004
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 42
Hantenna-tip ~ Hsp / 20.
Slow Quench ~ 10 sec. Fast Quench ~ 1 msec.
2 sec/div. 1 msec/div.
Pt
HOM2
Pr
PtPrHOM2
e-
At Eacc = 10 MV/m,ΔPo = 8 WP-loss (cal.) = 2 W x 2
Heating at HOM pick-up antenna
Slow Quenchτ
~ 10 sFast
Quenchτ
~ 1 ms
RecoveringTime> 30 min.
Transition from SC state to normal state occurred at the location isolated thermally.
1st test (long antenna) 2nd test(short antenna)
1st test (long antenna)
2nd test(short antenna)
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Design for CW Application needs
Lower the Magnetic Field at an Antenna.Improved Thermal Design
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KEK cERL Design H-Field Distribution
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conditions 15MV/m 20MV/m 25MV/m other
Antenna type : New , improve inner conductor (probe tip = 10 mm from HOM coupler center)
(1)c=10mm, u=5mmu=5mm
850~1000 A/m 1150~1350 A/m 1400~1650 A/m Probe gap=0.5mmOffset = 0mm
Antenna type : oldAntenna type : old c=0mm,c=0mm, u=0mm u=0mm (probe tip = 5 mm from HOM coupler center)
(0)c=0mm, (0)c=0mm, u=0mmu=0mm
24002400~~2850 A/m2850 A/m 30003000~~3500 A/m3500 A/m 37003700~~4400 A/m4400 A/m 0.5mm0.5mmOffset = 0mm
loop type : New , improve inner conductor (probe tip = 13 mm from HOM coupler center)
(1)c=10mm, u=3mm
1800~2050 A/m 2400~2720 A/m 3000~3360 A/m 0.5mm0.5mmOffset = 6mm
loop type : oldloop type : old c=0mm,c=0mm, u=0mm u=0mm (probe tip = 10 mm from HOM coupler center)
(0)c=0mm, (0)c=0mm, u=0mmu=0mm
22002200~~2400 A/m2400 A/m 29002900~~3150 A/m3150 A/m 35003500~~3850 A/m3850 A/m 0.5mm0.5mmOffset = 6mm
STF type : New , improve inner conductor (probe tip = 17 mm from HOM coupler center)
(1)c=10mm, u=2mm
----- ----- ----- Offset=10 mm
STF model : oldSTF model : old c=0mm,c=0mm, u=0mm u=0mm (probe tip = 13 mm from HOM coupler center, due to cut 2mm inner conductor )
(0)c=0mm, (0)c=0mm, u=0mmu=0mm
40004000~~4250 A/m4250 A/mHeating limit at CWHeating limit at CW
52005200~~5600 A/m5600 A/mNot use ? CW operationNot use ? CW operation
6800 6800 ~~
7200 A/m7200 A/mNot use ? CW operationNot use ? CW operation
0.5mm 0.5mm Offset=10 mm
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2 Stub HOM coupler for cERL
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Shuichi Noguchi, KEK SRF2009Tutorial, Berlin 47
Vertical Test
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Q0 -Eacc Curve for ERL 2-cell #1 @1.5K & 4.2K
48
11.3MV/m
30.1MV/mHOM #2 (antenna) heating
CouplersContentsRF Power Input CouplerCoupler Design & FabricationDesign Issues of Input CouplerBest Choice for SCMajor Couplers usedCoaxial Antenna CouplerSlide Number 9Slide Number 10Slide Number 11Coaxial Disk Type Window CouplerSlide Number 13STF-I & II CouplersSlide Number 15Slide Number 16Components�of Coaxial Antenna CouplerRF Design CriteriaSlide Number 19Slide Number 20Power Loss & E-Field StrengthRF Windows of Coaxial CouplerCoaxial Disk WindowCeramics WindowHFSS SimulationSlide Number 26Coupling / Tune-abilityDouble CouplersSuperpositionAt ResonanceOptimum CouplingProcessing ( Acceptance Test )Slide Number 33Slide Number 34HOM CouplerSlide Number 36Slide Number 37Slide Number 38High-pass Filter ( + Notch Filter )Slide Number 40Slide Number 41Slide Number 42Design for CW Application�needsSlide Number 44Slide Number 452 Stub HOM coupler for cERLSlide Number 47Slide Number 48