5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
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
ON/OFF mechanism
CLIC module RF network
3 dB splitter
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
11 11.2 11.4 11.6 11.850
40
30
20
10
0
Frequency, GHz
S11
, dB
F1
11.424 GHz choke mode flange prototype has been tested at SLAC up to 90 MW 200 ns.
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.
y
x
Throughout the design, reflection and matched radiation through the choke were minimized
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.
y ±0.25mm
y ±0.5mm
Choke flange with circular groove
choke Matched radiation
Reflection
S-p
aram
eter
s, d
B
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
Modified, double-sector choke flange
Frequency, GHz
S11
, dB
y
x
y ±0.5mm
x ±0.5mm
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
- 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
Choke flange. Other applications
Mini UHV gate valve
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
3dB H-plane splitterThe 11.424 GHz version of the splitter was tested at SLAC up to 150 MW x 260 ns.
Compact vacuum pumping port(design)
S11, dB
Radiation into the vacuum port
S-p
aram
eter
s, d
B
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
S11,S12
S13,S14 3 dB hybrids (WR90)
CLIC choice.32 MV/m surface E-field at 100 MW.
H-plane#1
H-plane#2
E-plane
SLAC-type
KEK-type
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
Cross Potent family
H-plane
E-plane
Hybrid solution
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
2 4 6 8 10 1250
40
30
20
10
0
Reflected
Transmitted
Stroke 7.7 mm
RF
po
we
r, d
B
Piston position (gap width), mm
ON
ON
OFF
OFF
Compact design of the high RF power variable (mechanically) reflector
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-p
aram
eter
s, d
BS
-par
amet
ers,
dB
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
0 20 40 60 80 1000
0.5
1
1.5
Variable reflector with compact H20 -> H01 mode convertor
Pha
se,
deg.
Am
plitu
de
PETS output signal
0 20 40 60 80 1000
0.5
1
1.5
Am
plitu
deP
hase
, de
g.
Time, ns
Time, ns
Time, ns
Time, ns
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
PETS ON/OFF operation
Power to the structure
Power extracted from the drive beam
The simulations have been done with HFSS, when the discrete current elements were representing the steady state current at a fixed frequency.
ON OFF
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
High RF power variable reflector. Other applications
11 11.5 12 12.5 13-70
-60
-50
-40
-30
-20
-10
0"OFF" case
Frequency [GHz]
S P
aram
eter
s [d
B]
S41
S31
S21
S11
11 11.5 12 12.5 13-70
-60
-50
-40
-30
-20
-10
0"ON" case
Frequency [GHz]
S P
aram
eter
s [d
B]
S41
S31
S21
S11
11 11.5 12 12.5 13-70
-60
-50
-40
-30
-20
-10
0"OFF" case
Frequency [GHz]
S P
aram
eter
s [d
B]
S41
S31
S21
S11
11 11.5 12 12.5 13-70
-60
-50
-40
-30
-20
-10
0"ON" case
Frequency [GHz]
S P
aram
eter
s [d
B]
S41
S31
S21
S11
11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13-70
-60
-50
-40
-30
-20
-10
0"OFF" case
Frequency [GHz]
S P
aram
eter
s [d
B]
S41
S31
S21
S11
11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13-70
-60
-50
-40
-30
-20
-10
0"ON" case
Frequency [GHz]
S P
aram
eter
s [d
B]
S41
S31
S21
S11
11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13-70
-60
-50
-40
-30
-20
-10
0"OFF" case
Frequency [GHz]
S P
aram
eter
s [d
B]
S41
S31
S21
S11
11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13-70
-60
-50
-40
-30
-20
-10
0"ON" case
Frequency [GHz]
S P
aram
eter
s [d
B]
S41
S31
S21
S11
11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13-70
-60
-50
-40
-30
-20
-10
0"OFF" case
Frequency [GHz]
S P
aram
eter
s [d
B]
S41
S31
S21
S11
11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13-70
-60
-50
-40
-30
-20
-10
0"ON" case
Frequency [GHz]
S P
aram
eter
s [d
B]
S41
S31
S21
S11
11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13-70
-60
-50
-40
-30
-20
-10
0"OFF" case
Frequency [GHz]
S P
aram
eter
s [d
B]
S41
S31
S21
S11
11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13-70
-60
-50
-40
-30
-20
-10
0"ON" case
Frequency [GHz]
S P
aram
eter
s [d
B]
S41
S31
S21
S11
Variable attenuator(phase shifter)
Variable splitter
Load(short circuit)
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
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
tangential
normal
15 MW SiC
5th Collaboration Meeting on X-band Accelerator Structure Design and Test Program. May 2011
X-band high peak power (>50 MW) broadband ‘dry’ stainless steel load.
0 100 200 3000
50
100
150
Distance, mm
dT, d
egre
s (1
35M
W, 2
40ns
)100
27510
Pulsed heating distributions along the load:
H-field plot (quarter of the period)
Design specifics
Load regular part cross section
E
The load half
Matching taper
WR90
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).
Loads #36-39Green – designRed - measured