Fabrication and measurement of RF components for CLIC study

Thapakron Pulampong Physics department, Khon-Kaen University, Thailand

18/8/2010

CERN summer school programme 2010

• RF flanges + straight waveguides Objective: To study how Cu-plating (12-15 µm) of RF flanges affects

vacuum and RF properties after brazing with straight waveguides.

- brazing- vacuum leak test- RF measurement

• Diffusion bonding study (PSI prototype disks) Objective: To study diffusion bonding quality using metallographic observation.

- chemical cleaning for disks- diffusion bonding process- metallographic observation

RF flanges + Straight waveguides

Cu layer12-15 µm

Machining->Chemical cleaning-> Ni-plating -> Cu-plating

Machining->Chemical cleaning

Brazing of RF flanges with a waveguide

• With brazing wire Ag/Cu/Pd at 810-820 °C (Bodycote)

(Silver/Copper/Palladium)

Under vacuum

Structure after brazing

Vacuum leak testClean bolts and nuts with alcohol and ultrasound 20 minutes

Clean vacuum flanges with alcohol

Connect vacuum flanges with the structure

Vacuum leak detector

With A.Olyunin

Customer:CERN BE/RF Object: RF flanges and straight waveguide

Leak testdate:

19.07.2010

Leak detector type: LEYBOLD L200⁺ .Reference leak rate: 6.2±15% ×10⁻⁷mbar×L/sMinimum detectable leak rate: 1×10⁻¹¹ mbar×L/sTracer gas: Helium 99%System pressure: 1×10⁻³ mbarTest temperature: 20 C ̊�

Brazing

Max. measured leak rate: 3.6×10-11 mbar×L/s

CERN TE/VSC LEAK TEST CERTIFICATEDescription of examination

Examined part

Results

Good results!

RF measurement

Connect RF test flanges with RF flanges +waveguide RF test flanges

Clean all surface to be connected with alcohol

RF flanges+waveguide

Connect network analyzer with the sample and start testing

2ports network analyzerCalibrated before test

With A.Olyunin

RF measurement result

Frequency(GHz)

S-parameter (dB)S11 S22

11.4240 -31.029 -31.27311.9920 -29.395 -29.884

Good results!

Diffusion bonding test

Stack no.2 with 1 insert for test validation process of bonding or brazing.

Regular cell disk: 2-46

Wake monitor cell disk:8-43

Wake monitor dell disk:5-40

Wake monitor cell disk:4-37

Wake monitor cell disk:3-36

Regular cell disk: 2-35

INSERT1 INSERT2

Standard cell disk 2-55

Standard cell disk 2-55

Standard cell disk 2-55

Standard cell disk 2-55

Standard cell disk 2-55

Bonding temperature : 1040 °C Time : 1h 30m Atmosphere : H2

Stack no.1

Prototype disks for PSI accelerating structures

Chemical cleaning procedure

Degreasing with detergent NGL 17.4

spec. ALU III and ultrasound

Deoxidation with HCl acid

Etching with SLAC solution

Dry with nitrogen gas

Dry with oven

Final rinsing with demineralised water

and ultrasound With M.Balabaila

Vacuum before H2 injection for diffusion bonding

Primary pump 10-1 torr

Root pump 10-3 torr

Diffusion pump 10-6 torr

Bodycote

Diffusion bondingHeating system made of Molybdenum screens (melting point is 2617.0 °C): temperature of 1040 °C for the bonding process.

Cool downCooling system is composed of water cooling and air cooling.

Water spray

Cooling turbine

Air tank

Because of water spray and cooling turbine, the temperature can be reduced rapidly.

Diffusion bonding no.1

4 temperature probes (thermo-couples) in tuning holes

CERAMICS

Vacuum H2 Heat up to 1040 C weight of 16 Kg

Furnace warm up and clean up ceramics and support before bonding.

Bonding process 1:30h

Diffusion bonding no.2

CERAMICS

weight of 16 Kg

Furnace warm up and clean up before bonding.

Bonding process 1:30h2 temperature probes (thermo-couples)

Stacks after BondingStack no.1

Stack no.2 with 1 insert

SOI 1

SOI 2

SOI 4

SOI 5SOI 6

SOI 7

Metallographical observation Bonding no.1

Contact reference line

Stack no.1 after cutting

M. Aicheler

SOI 1

SOI 2

SOI 3

SOI 5SOI 6

SOI 7

12345

Metallographical observation Bonding no.2

Installed insert before bonding process after cutting

Stack no.2 after cutting

M. Aicheler

Stack no.2 metallographic observation

Grain crossingGrain crossing

Designed contact zone Designed contact zone

Joint no. 4 Joint no. 5

Contact reference line

M. Aicheler

Conclusion

• Vacuum leak 3.6× 10-11 mbar·l/s (< 10-10 )( Good)• RF reflection about -30 dB (Good)

RF flanges + straight waveguides

Bonding tests• Successful: grain crossing can be found in areas with and without designed contact.• Inserts should not be diffusion bonded, but brazed, as originally foreseen.