IHEP High Power Input Coupler Activity Report
Huang Tong-ming (黄彤明)
IHEP High Power Input Coupler Group
First Mini-workshop on IHEP 1.3 GHz Superconducting RF project
June 10th, 2009, Beijing
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
个
• 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.
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
Ceramic window
The ceramic
window is usually
located at the
minimum E-filed
of the standing
wave mode.
Tristan-type window optimization
Radial electric field of the ceramic window
dc=2 mm
dc=4 mm
dc= 6 mm
Electric field (V/m)
500000
400000
300000
200000
100000
The area near Choke tip
0
-10
0
10
20
30
40
Radial distance (mm)
50
60
70
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.
Impedance matching optimization
(b) 1.002
rw , f0
1.000
f0=500MHz
rw=171mm
rw=166mm
Mag(S21)
0.998
0.996
rw=176mm
0.994
0.992
0.990
490
492
494
496
498
500
502
504
506
508
510
Frequency (MHz)
(c)
0
0
1.000
h=94.5mm
0.999
0.998
h=90mm
0.997
0.996
0.995
0.994
0.993
0.992
h=99mm
0.991
0.990
0.989
0.988
0.987
0.986
0.985
0.984
488 490 492 494 496 498 500 502 504 506 508 510 512
f =500MHz
Frequency (MHz)
r_doorknob ,f0
(d)
1.000
f0=500MHz
r_doorknob=20mm
0.999
0.998
Mag(S21)
h ,f
Mag(S21)
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.
r_doorknob=15mm
0.997
r_doorknob=10mm
0.996
0.995
0.994
488 490 492 494 496 498 500 502 504 506 508 510 512
Frequency(MHz)
Qe calculation
Conclusion:
The results provide theoretical instruction for
coupler input port design and the positioning
of the antenna penetration depth.
1.000000E+07
3.000E+06
radius_10
radius_15
2.500E+06
2.000E+06
1.000000E+06
Qext
10*logQext
measured
simulation
1.500E+06
1.000E+06
1.000000E+05
5.000E+05
0.000E+00
-32.7 -27.7 -22.7 -17.7 -12.7 -7.7
1.000000E+04
-33
-28
-23
-18
-13 -7.7 -2.7 2.3
-2.7
2.3
7.3
12.3
17.3
22.6
27.6
29.6
7.3 12.3 17.3 22.6 27.6 29.6
antenna penetration(mm)
antenna penetration(mm)
4.500E+06
7.000E+06
4.000E+06
6.000E+06
3.500E+06
5.000E+06
Dia_SBP 220
Dia_SBP 200
2.000E+06
Qext
2.500E+06
4.000E+06
D_215.25
D_225.25
3.000E+06
1.500E+06
1.000E+06
2.000E+06
5.000E+05
1.000E+06
0.000E+00
-3
2.
7
-2
7.
7
-2
2.
7
-1
7.
7
-1
2.
7
-7
.7
-2
.7
2.
3
7.
3
12
.3
17
.3
22
.6
27
.6
29
.6
Qext
3.000E+06
antenna penetration(mm)
0.000E+00
-33 -28 -23 -18 -13 -7.7 -2.7 2.3 7.3 12.3 17.3 22.6 27.6 29.6
antenna penetration(mm)
Multipacting simulation
Tri-plots about the counter function,
final impact energy of the window:
Electron trajectory of the window :
Conclusion:
By simulation, a one order MP appears on the vacuum side of the
window at mixed wave mode.
Thermal simulation
RF heat of the coupler for BEPCII SCC
Calculated Dynamic losses
160
inner conductor
outer conductor
ceramic
140
50
100
150
200
250
300
Dynamic loss W）
Window
26
52
77
103
129
155
Inner conductor
26
51
77
102
128
153
120
RF heat(W)
Pin（kW）
Y =0.004+0.51043 X
100
Y =0.08+0.26526 X
80
60
40
Y =0.064+0.22209 X
20
Outer conductor
11
22
33
45
56
67
0
50
100
150
200
Pin(kW)
Temperature distribution
Thermal Stress distribution
250
300
Fabrication
The fabrication flows of the inner conductor and the
window:
OFHC window
parts machining
Ceramic
window frame
machining
Stainless steel
parts machining
Clean
Copper-copper
brazing
Ceramiccopper brazing
Clean
Clean
Copper or
nickel plating
Window
subassemblies
leak check
Window
subassemblies
leak check
Steel-copper
brazing
Ceramic TiN
coating
The whole
window
brazing
Window
subassemblies
leak check
Antenna and
window EBW
Stainless steel water
cooling pipes
machining
Clean
TIG
Subassemblies
leak check
The whole antenna EBW
OFHC antenna
parts machining
Clean
Final assembly
leak check
and storage
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
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.
TiN coating
Brazing and welding
Steel- copper brazing
99.5% Al2O3ceramiccopper brazing
AuCu(65%) at 1020
Ag at 962
The whole window brazing
Copper- copper brazing
AuCu(65%) at 1020
AuCu(20%) at 889 , AgCu(28%) at 779
Brazing and welding, cont.
TIG (Tungsten-arc inert-gas welding)
EBW (electron beam welding)
The ceramic shield before EBW (left) and after EBW (right)
Leakage checking and surface cleaning
Subassemblies leak check
Final assembly leak check
OFHC parts after cleaning
Assembly is processed in a
class 100 clean room
Test Results
The two key components (window and inner conductor)
were 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
200kW after conditioning
Electron 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
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.
TTF III @DESY
ERL @Cornell
电容型 @KEK STF baseline型@KEK
IHEP 1.3GHz SCC coupler
Frequency
1.3 GHz
Max Power
Test：1MW，Pulsed
（for ILC）
Oper：300 kW，Pulsed
Pulse length & rep.rate
Test：1.5msec，5Hz
（for ILC）
Oper：1.5msec，5Hz
Q e for ILC
2  10 6
低温系统
低电平控制系统
功率源系统
真空系统等
低温恒温器
高功率输入
耦合器
超导腔和调谐器
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
78
39
110
R3
R 10
R 14
82.55
7.0
4
104
40
45.2
R 1.6
R 2.0
19
R 2.0
3
4
Two parameters belong to the
doorknob( highlighted with yellow)
have been modified to get the
optimum power transmission
performance.
4
R7.0
23
Warm Part RF Structures
Warm window
1.0
R 22.6
R 52
10
50
104
45.2
116
R 2.0
6.6
50
28
3.0
R 1.5
30
25
50
44
6.6
R 22
Try to reduce the number
of bellows from 4 to 2:
only one bellow on each
conductors?
10
R 1.5
R 15
R 58
1
R 3.0
303
35.2
3.0
6.0
Inner conductor
9.0
R 1.25
5.0
2.0×9
Bellow
20
R1
2.5
2.5×11
113
Outer conductor
R 17.6
R 40.5
R1
R 1.25
Outer conductor
Inner conductor
81
Cold Part RF Structures
R 17.6
R 40.5
10
50
35.2
R2
25
35
Cold window
30
R 17.3
1
R 46
50
26
60
40
7
17.4
R 11
R 2.3
Outer conductor
40
R 1.5
6.2
50
3
20
R 1.25
1
Inner conductor
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
1MW @TW
Try to reduce the E-field
on ceramic surface,
especially air side.
RF Performance
Power transmission performance
Maximum Mag_E on ceramic
air side is 1.28e6 V/m, @ 1MW,
TW, 115deg
Before optimize
After optimize
Mesh check
1.0
1400000
1200000
Abs(Mag_E)
0.8
Mag(S21)
Radial E-field distritubion on ceramic air side
0.6
0.4
0.2
1000000
800000
600000
400000
0.0
200000
1.1
1.2
1.3
1.4
1.5
Frequency (GHz)
Mag(S21)=0.9979@1.3GHz
0
10
20
30
Radial distance (mm)
40
50
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
E-field distribution on Z-Plane
H
D
field magnitude along the on axis curve
Parameters 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;
 beam tube = 80mm
 input port = 40 mm
Distance from end-cell = ‘D’
The radius of antenna = 3mm
Coaxial line = 50 W
Qext
1.4000E+07
1.2000E+07
1.0000E+07
8.0000E+06
D=40mm
D=45mm
D=50mm
6.0000E+06
4.0000E+06
2.0000E+06
0.0000E+00
0
1
2
3
4
5
6
7
8
9
10
Part III:
Some questions to be consulted
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?
If the crest is wide enough (~2-3 mm), it
may be able to support a MP buildup, or
MP may jump across
one MP resonance
conditioned satisfied at
operating power on flat
wall
Bellows or Steps May
Lead to More Pervasive
Multipacting
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
“Coupler component Test stand Activities at SLAC/ LLNL”, TTC meeting @ KEK,
WG1-input coupler, 2006
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.
Question5:
Why does KEK STF coupler make a independent Vacuum in the inner
conductor, since it results in DC bias impossible?
Warm window
Cold window
Beam pipe
Doorknob
conversion
5K cooling
Vacuum port
80K cooling
Independent Vacuum? Why?
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 method
used in bellow
connecting?
What’s the sealing
gasket of the flange?
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
A or B?
B
TiN coating
Question10:During brazing and welding, is there any metal
vapor coming from? If there is, how to protect the ceramic?
protection mask for ceramic and RF surface, TTF-III coupler
e-beam
for support and removal
shielding against metal vapor
ceramic with copper collars
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)?
4 bellows
2 bellows
Question 12:
• what’s the stainless steel type? 316L
or 316LN?