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