Review of waveguide components development for CLIC
I. Syratchev, CERN
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
• Many hundred thousands of waveguide components are
needed for CLIC. The fabrication cost and waveguide network
logistic are serious issues that are needed to be addressed to
make an optimal RF waveguide distribution system.
• The RF network in CLIC connects at a short distance (~ 0.5 m)
broadband decelerating structure (PETS) and narrowband
accelerating structure. Thus, all the waveguide components
should be optimised to avoid parasitic circulation of the reflected
signals in a system.
• We have developed the special RF components to provide
specific to CLIC operational properties.
• In general, the particular choice of individual components could
seriously affect the RF network layout and cost.
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
CLIC module RF network
ON/OFF mechanism
3 dB splitter
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
Choke flange with circular groove
To allow the independent transverse alignment of the two linacs in CLIC, the special, contact-free choke mode
flanges are planned to be used. By specification, the 0.25 mm transverse misalignment should be tolerated.
Throughout the design, reflection and matched radiation
through the choke were minimized
S-parameters, dB
11.424 GHz choke mode flange prototype has
been tested at SLAC up to 90 MW 200 ns.
Reflection
Matched radiation
choke
In this geometry shift along narrow wall of the waveguide causes severe coupling to
the trapped TM02 mode, which is close to the operating frequency.
0
F1
y ±0.5mm
S11, dB
10
20
30
y ±0.25mm
40
y
50
11
11.2
11.4
11.6
11.8
x
Frequency, GHz
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
S11, dB
Modified, double-sector choke flange
y ±0.5mm
x ±0.5mm
y
x
Frequency, GHz
The new geometry allows for ±0.5mm sheer
shift in both directions. It also can tolerate
twist <10 and kink < 30. Matched radiation
through the choke is below -40 dB.
The slot is 2.5 mm wide.
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
Choke flange. Other applications
Mini UHV gate valve
- Ready to be used as a part of the compact RF/vacuum valve.
- Building block of the RF phase stable long waveguide line. It will naturally
compensate the thermal expansion without introducing extra RF phase advance.
- Rotatable (3600) high RF power waveguide contact free joint (with circular grove).
Designed for C-band medical accelerator.
Polarizer converts H10 in rectangular
WG into rotating H11 in a circular WG
Choke flange
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
3dB H-plane splitter
The 11.424 GHz version of the splitter was
tested at SLAC up to 150 MW x 260 ns.
Compact vacuum pumping port
(design)
S-parameters, dB
S11, dB
Radiation into
the vacuum port
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
H-plane#1
S13,S14
3 dB hybrids (WR90)
SLAC-type
S11,S12
H-plane#2
KEK-type
E-plane
CLIC choice.
32 MV/m surface E-field at 100 MW.
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
Cross Potent family
H-plane
Hybrid solution
E-plane
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
Compact design of the high RF power variable (mechanically) reflector
0
ON
Transmitted
OFF
 20
 30
Reflected
Stroke 7.7 mm
 40
 50
2
4
6
8
10
12
ON
OFF
S-parameters, dB
Piston position (gap width), mm
Radiation through
the chokes
The variable reflector is a core element of
the PETS ON/OFF mechanism. It is
activated when the local termination of the
RF power production in PETS is required.
S-parameters, dB
RF power, dB
 10
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
Influence of the external waveguide circuit bandwidth on the PETS RF power production
Variable reflector with compact H20 -> H01 mode convertor
PETS output signal
1.5
1
Amplitude
Amplitude
1.5
0.5
0
0
20
40
60
80
100
0.5
0
Time, ns
0
20
40
60
Time, ns
Phase, deg.
Phase, deg.
1
Time, ns
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
Time, ns
80
100
PETS ON/OFF operation
ON
OFF
Power extracted
from the drive beam
Power to the structure
The simulations have been done with HFSS, when
the discrete current elements were representing the
steady state current at a fixed frequency.
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
High RF power variable reflector. Other applications
Variable splitter
Variable attenuator
(phase shifter)
Load
(short circuit)
"OFF" case
0
S Parameters [dB]
-10
-20
-30
-40
S41
-50
-60
S31
S21
S11
12
Frequency [GHz]
12.5
"OFF" case
13
"ON" case
"OFF" case
0
0
-10
-10
"OFF" case
0
0
-10
-10
-20
-20
S Parameters [dB]
11.5
S Parameters [dB]
-70
11
-30
-40
S41
-50
-30
-40
S41
-50
-50
-60
S31
S21
S41
-50
-60
11.5
12
Frequency [GHz]
12.5
13
11.2
11.4
S11
11.6
11.8
12
12.2
Frequency [GHz]
12.4
12.6
12.8
-70
11
13
11.2
11.4
11.6
11.8
12
12.2
Frequency [GHz]
12.4
12.6
12.8
13
12.4
12.6
12.8
13
-40
S11
-70
11
-70
11
-30
-70
11
"OFF" case
"OFF" case
"ON" case
0
0
S21
-10
-10
-10
-10
S11
-20
-20
-20
-20
11.5
-30
-40
12
Frequency [GHz]
12.5
13
S41
-50
S31
-60
-30
-40
11.2
11.4
11.6
-30
-40
-50
S41
-50
-60
-60
S21
S11
-70
11
0
S41
11.8
12
12.2
Frequency [GHz]
12.4
12.6
12.8
13
-70
11
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
S11
-70
11
11.2 11.4
-30
-40
S41
-50
S31
S31
S21
"ON"
case
0
-10
"ON" case
0
S31
S Parameters [dB]
S41
S21
-60
S11
S Parameters [dB]
-40
S31
S21
-60
S Parameters [dB]
-30
-20
S Parameters [dB]
S Parameters [dB]
S Parameters [dB]
S31
-20
S31
S21
S21
-60
S11
11.2
11.6
11.4 11.6 11.8
12
12.2 12.4 12.6
11.8
12
12.2 12.4 12.6 12.8
13
Frequency [GHz]
Frequency [GHz]
S11
12.8
13
-70
11
11.2
11.4
11.6
11.8
12
12.2
Frequency [GHz]
X-band moderate peak power ‘dry’ RF load with SiC absorber (design).
The 15 MW peak RF power loads are the most common components in CLIC module.
~ 350 000 loads will be needed for 3 TeV CLIC option.
100 mm
Max. E-fields on the ceramic surface
15 MW
normal
tangential
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
SiC
X-band high peak power (>50 MW) broadband ‘dry’ stainless steel load.
Design specifics
Pulsed heating distributions
along the load:
150
dT, degres (135MW, 240ns)
H-field plot
(quarter of the
period)
We have received about 50 loads. The companies provide very reproducible
results with reflection <-30dB at frequencies above 11.35 GHz. The loads
have been tested up to 60MWx400ns (KEK) and 25MWx1600ns (SLAC).
10
275
100
100
50
0
Loads #36-39
0
100
200
300
Distance, mm
The load half
Load regular part
cross section
WR90
Matching taper
E
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
Green – design
Red - measured