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IHEP High Power Input Coupler Activity Report. Huang Tong-ming ( 黄彤明 ). First Mini-workshop on IHEP 1.3 GHz Superconducting RF project June 10th, 2009, Beijing. IHEP High Power Input Coupler Group. Outline. - PowerPoint PPT Presentation
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IHEP High Power Input Coupler Activity Report
First Mini-workshop on IHEP 1.3 GHz Superconducting RF project
June 10th, 2009, Beijing
IHEP High Power Input Coupler Group
Huang Tong-ming ( 黄彤明 )
Outline• The construction of the high power input coupler
for BEPCII 500MHz superconducting cavity;• The preliminary consideration about the input
coupler for IHEP 1.3GHz superconducting RF project;
• Some questions to be consulted.
Part I:
The Construction of the High Power Input Coupler for BEPCII 500MHz Superconducting Cavity;
Design
• Considering the short time available for the BEPCII construction, the high power input coupler is modified based on the KEKB 508MHz coupler.
• In the following, some simulation works will be listed.
个
1. doorknob cover;2. doorknob;3. DC-bias component;4. ceramic;5. outer conductor;6. inner conductor;7. water-cooling pipes;8, window;9. monitor ports for vacuum 、 Arc and electron ;10. BEPCII 500MHz superconducting cavity.
Window position
The ceramic window is usually located at the minimum E-filed of the standing wave mode.
Ceramic window
Tristan-type window optimization
-10 0 10 20 30 40 50 60 700
100000
200000
300000
400000
500000
Radial electric field of the ceramic window
Ele
ctri
c fie
ld (
V/m
)
Radial distance (mm)
dc=2 mm dc=4 mm dc= 6 mm
The area near Choke tip
Conclusion: • The E-field near the choke tip
increases obviously, so the distance from the choke tip to the ceramic surface should be carefully selected.
• The H-field gratitude along the ceramic radius is high, especially the H-field on the inner conductor is quite high, so the dimension of the ceramic window inner conductor is not allowed to be too small.
490 492 494 496 498 500 502 504 506 508 510
0.990
0.992
0.994
0.996
0.998
1.000
1.002
rw=171mm
Mag
(S21
)
Frequency (MHz)
rw=176mm
rw=166mm
rw f0,
f0=500MHz
(b)
488 490 492 494 496 498 500 502 504 506 508 510 5120.9840.9850.9860.9870.9880.9890.9900.9910.9920.9930.9940.9950.9960.9970.9980.9991.000
h=99mm
h=94.5mm
Mag
(S
21)
Frequency (MHz)
h ,f0
h=90mm
(c)
f0=500MHz
488 490 492 494 496 498 500 502 504 506 508 510 512
0.994
0.995
0.996
0.997
0.998
0.999
1.000
r_doorknob=15mm
r_doorknob=20mm
Mag
(S21
)
Frequency(MHz)
r_doorknob ,f0
r_doorknob=10mm
(d)f0=500MHz
Impedance matching optimization
Conclusion:
• ‘rw’, ‘h’, ‘r_doorkonb’ have a great impact to the central frequency;
• the parameter “h” is changed to 94.5mm to shift the central frequency to 500MHz.
1.000000E+04
1.000000E+05
1.000000E+06
1.000000E+07
-33 -28 -23 -18 -13 -7. 7 -2. 7 2. 3 7. 3 12.3 17.3 22.6 27.6 29.6
antenna penetrati on(mm)
10*l
ogQe
xt
measuredsi mul ati on
0. 000E+00
5. 000E+05
1. 000E+06
1. 500E+06
2. 000E+06
2. 500E+06
3. 000E+06
-32. 7 -27. 7 -22. 7 -17. 7 -12. 7 -7. 7 -2. 7 2. 3 7. 3 12. 3 17. 3 22. 6 27. 6 29. 6
antenna penetrati on(mm)
Qext
radi us_10radi us_15
0. 000E+00
5. 000E+05
1. 000E+06
1. 500E+06
2. 000E+06
2. 500E+06
3. 000E+06
3. 500E+06
4. 000E+06
4. 500E+06
antenna penetrati on(mm)
Qext Di a_SBP 220
Di a_SBP 200
0. 000E+00
1. 000E+06
2. 000E+06
3. 000E+06
4. 000E+06
5. 000E+06
6. 000E+06
7. 000E+06
-33 -28 -23 -18 -13 -7. 7 -2. 7 2. 3 7. 3 12. 3 17. 3 22. 6 27. 6 29. 6
antenna penetrati on(mm)
Qext D_215. 25
D_225. 25
Qe calculationConclusion:
The results provide theoretical instruction for coupler input port design and the positioning of the antenna penetration depth.
Multipacting simulation
Electron trajectory of the window :Tri-plots about the counter function, final impact energy of the window:
Conclusion:
By simulation, a one order MP appears on the vacuum side of the window at mixed wave mode.
Thermal simulation
Pin(kW)
Dynamic loss W)
50 100 150 200 250 300
Window 26 52 77 103 129 155
Inner conductor 26 51 77 102 128 153
Outer conductor 11 22 33 45 56 67
Temperature distribution
Thermal Stress distribution
Calculated Dynamic losses
50 100 150 200 250 3000
20
40
60
80
100
120
140
160
RF heat of the coupler for BEPCII SCC
Y =0.08+0.26526 X
Y =0.064+0.22209 X
Y =0.004+0.51043 X
RF
hea
t(W
)
Pin(kW)
inner conductor outer conductor ceramic
Fabrication
Clean
Ceramic window frame
machiningClean
Ceramic-copper brazing
Ceramic TiN coating
The whole window brazing
Stainless steel parts machining
CleanCopper or
nickel plating
OFHC window parts machining
Copper-copper brazing
Window subassemblies
leak check
Window subassemblies
leak check
Steel-copper brazing
Window subassemblies
leak check
Stainless steel water cooling pipes
machiningClean TIG
Subassemblies leak check
OFHC antenna parts machining
Clean
Antenna and window EBW
Final assembly leak checkand storage
The whole antenna EBW
The fabrication flows of the inner conductor and the window:
Copper plating and TiN coating
Copper plating A good sample (left) and a bad sample (right) of copper plating: bubbles on the bad sample due to too high current
TiN coating
A plate shape Ti target acted as anode and the outer conductor of the window as the cathode. The desired film thickness is 8 nm.
Copper- copper brazing
AuCu(65%) at 1020
The whole window brazingAuCu(20%) at 889 , AgCu(28%) at 779
Brazing and welding
99.5% Al2O3ceramic- copper brazing
Ag at 962
Steel- copper brazing
AuCu(65%) at 1020
TIG (Tungsten-arc inert-gas welding)
EBW (electron beam welding)
The ceramic shield before EBW (left) and after EBW (right)
Brazing and welding, cont.
Leakage checking and surface cleaning
Subassemblies leak check Final assembly leak check
Assembly is processed in a
class 100 clean room OFHC parts after cleaning
Test ResultsThe two key components (window and inner conductor) wer
e fabricated in China and then received high power test in KEK. Professor Takaaki Furuya has given us great help about the test. The maximum power reached is 270kW in CW.
Test result (Cont.) No electron and outgasing were found at CW of 20
0kW after conditioningElectron current state: Keeping power test at 100kW ,150kW and
200kW
Part II:
The preliminary consideration about the
input coupler for IHEP 1.3GHz
superconducting RF project
IHEP 1.3GHz SCC couplerTTF III @DESY ERL @Cornell
STF baseline 型 @KEK电容型 @KEK
Through carefully investigating and considering our fabrication experiences, we choose the STF baseline type coupler as IHEP 1.3GHz coupler design prototype in the first research phase.
超导腔和调谐器
高功率输入耦合器
低温恒温器
真空系统等
功率源系统
低电平控制系统
低温系统
Frequency 1.3 GHz
Max Power
(for ILC)
Test:1MW,Pulsed
Oper:300 kW,Pulsed
Pulse length & rep.rate
(for ILC)
Test:1.5msec,5Hz
Oper:1.5msec,5Hz
eQ for ILC 6102
What have done• Preliminary RF structures have been
calculated.
• Coupling factor calculation has been finished decide the coupler port position
Transition taper
Cold part Warm part doorknob
Doorknob RF Structures
85
784
39
R 14R 10
R 3
40
45.2R 1.6 R 2.0
82.5
5
110
104
7.0
4
4
R 2.0
23
3
R7.0
19
Two parameters belong to the doorknob( highlighted with yellow) have been modified to get the optimum power transmission performance.
104
11645.2
44 6.6
50
50
303
35.2
5010
2011
3Warm Part RF Structures
R 2.01.0
3.0
R 1.5
6.6
R 52 R 22.6
R 15R 58
25 28
R 22
10
R 1.5
R 3.01
30Inner conductorOuter conductor
R 1.25
6.0
2.5×
11
2.5
R 1.25
2.0×
9
R 1
R 1
3.0R 40.5
9.0
R 17.6
5.0
Inner conductorOuter conductor
Bellow
Warm window
Try to reduce the number of bellows from 4 to 2: only one bellow on each conductors?
Cold Part RF Structures
81
35.2
5035
5050
407
60
26
40
17.4
R 40.5 R 17.6
R 17.3
10
20
3
6.2
R 1.25
R 21
R 1.5
R 2.3 1
R 11R 46
25
30
Inner conductorOuter conductor
Cold window
In order to match with the 40mm coupler input port, a tapper was used to transit the coaxial diameter from 60mm to 40mm.
E-field and H-field distribution
1MW @TW
Try to reduce the E-field on ceramic surface, especially air side.
1MW @TW
RF Performance
1.1 1.2 1.3 1.4 1.50.0
0.2
0.4
0.6
0.8
1.0
Ma
g(S
21
)
Frequency (GHz)
Before optimize After optimizeMesh check
Power transmission performance
0 10 20 30 40 50
200000
400000
600000
800000
1000000
1200000
1400000 Radial E-field distritubion on ceramic air side
Ab
s(M
ag
_E
)
Radial distance (mm)
Mag(S21)=0.9979@1.3GHz
Maximum Mag_E on ceramic air side is 1.28e6 V/m, @ 1MW, TW, 115deg
Qe calculation
• This work discusses the positioning of the high power input coupler for IHEP 1.3GHz 9-cell SCC. It examines the method used to reduce the model to enable faster solutions whilst still maintaining accurate results.
In order to faster solving, the model was reduced to 4.5-cell since Qe scales with the number of cells. The field flatness in every cell should be assured before the coupling analysis. Two parameters related with Qe were studied: 1) the coupler input port position; 2) the antenna penetration depth
Model of 4.5-cell and simplified coupler
field magnitude along the on axis curve
E-field distribution on Z-Plane
D
HParameters related with Qe
Qe calculation Plotted results
• To obtain the optimum 2×106 , we can:– Chose the distance from
end cell to coupler port center D=40mm, adjust the antenna penetration near 4mm;
– Chose the distance from end cell to coupler port center D=45mm, adjust the antenna penetration near 7mm;
– Chose the distance from end cell to coupler port center D=50mm, adjust the antenna penetration near 10mm;
0. 0000E+00
2. 0000E+06
4. 0000E+06
6. 0000E+06
8. 0000E+06
1. 0000E+07
1. 2000E+07
1. 4000E+07
0 2 4 6 8 10
1 3 5 7 9
beam tube = 80mm input port = 40 mm Distance from end-cell = ‘D’The radius of antenna = 3mm Coaxial line = 50
Part III:
Some questions to be consulted
one MP resonance conditioned satisfied at operating power on flat wall
If the crest is wide enough (~2-3 mm), it may be able to support a MP buildup, or MP may jump across
Based on scaling, for a given bellows undulation or step, more MP resonances may be supported simultaneously, potentially increasing the conditioning area and gas load
Question 1: Have you done MP simulation? 2D or 3D simulation? Tools?Did you find MP occurs inside the coupler, especially on the bellow area during high power test? How to avoid MP?
“Coupler component Test stand Activities at SLAC/ LLNL”, TTC meeting @ KEK, WG1-input coupler, 2006
Bellows or Steps May Lead to More Pervasive Multipacting
Question2:
What’s the fabrication difficulties?
• Copper Plating on Bellows?
• Vacuum sealing of bellows?
• Other?
Question3:About ceramic:
• KEK coupler choose 95% Al2O3, why don’t you choose high purity ceramic?
• Is the thermal shock tests of the ceramic necessary? Put into liquid nitrogen repeatedly: repeated times?
Thermal Shock Test
Question4: Does the dimension shrinking from room temperature to cryo-temperature impact the power transmission performance?
Why is the central frequency a little below 1.3GHz? Does it have relationship with dimension shrinking?
My guess: Right?
The RF structures simulated
are at room temperature and after cooling down, the central frequency will shift to 1.3GHz.
5K cooling80K cooling
Beam pipe
Warm window
Doorknob conversion
Cold window
Vacuum port
Independent Vacuum? Why?
Question5:
Why does KEK STF coupler make a independent Vacuum in the inner conductor, since it results in DC bias impossible?
Questions 6 and 7:What kind of sealing gasket of flanges used between warm and cold parts, doorknob and warm parts connecting?What kind of method used in bellow connecting? Brazing or welding?
What’s the sealing gasket of the flange?
What’s the method used in bellow connecting?
Question8: Except copper plating, does the coaxial lines received other plating, e.g. ion plating? Plating method? Thickness?
One of trial to reduce electron multipactoring amplitude, Ti ion plate with ~2-µm applied (gold color) to the inner and outer conductors for the coaxial transmission line.
TTC at KEK
Question 9: When does TiN been coated on ceramic vacuum side? Before whole window assembled or after? What’s method used in TiN coating?
A TiN coating
B TiN coating
A or B?
Question10:During brazing and welding, is there any metal vapor coming from? If there is, how to protect the ceramic?
e-beam
ceramic with copper collars
shielding against metal vapor
for support and removal
protection mask for ceramic and RF surface, TTF-III coupler
ERL mini-workshop at Beijing University, 7th – 8th November 2005
Question 11: Is it necessary to use four bellows? Why not just use two bellows (it’s similar with TTF-III coupler)?
2 bellows4 bellows
Question 12:
• what’s the stainless steel type? 316L or 316LN?
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