1. Fabrication and measurement of RF components for CLIC study
CERN summer school programme 2010
Fabrication and measurement of RF components for CLIC study
Thapakron Pulampong
Physics department, Khon-Kaen University, Thailand
18/8/2010

2. 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

3. RF flanges + Straight waveguides
Machining->Chemical cleaning
Cu layer12-15 µm
Machining->Chemical cleaning-> Ni-plating -> Cu-plating

4. Brazing of RF flanges with a waveguide
Under vacuum
With brazing wire Ag/Cu/Pd at °C (Bodycote)
(Silver/Copper/Palladium)
Structure after brazing

5. Vacuum leak test With A.Olyunin
Clean bolts and nuts with alcohol and ultrasound 20 minutes
Clean vacuum flanges with alcohol
Vacuum leak detector
Connect vacuum flanges with the structure

6. Object: RF flanges and straight waveguide
CERN TE/VSC LEAK TEST CERTIFICATE
Description of examination
Customer:
CERN BE/RF
Object: RF flanges and straight waveguide
Leak test
date:
Leak detector type: LEYBOLD L200⁺ .
Reference leak rate: ±15% ×10⁻⁷mbar×L/s
Minimum detectable leak rate: 1×10⁻¹¹ mbar×L/s
Tracer gas: Helium 99%
System pressure: ×10⁻³ mbar
Test temperature: ̊C
Examined part
Brazing
Results
Max. measured leak rate: × mbar×L/s
Good results!

7. RF measurement With A.Olyunin RF flanges+waveguide RF test flanges
Clean all surface to be connected with alcohol
Connect RF test flanges with RF flanges +waveguide
Connect network analyzer with the sample and start testing
RF test flanges
2ports network analyzer
Calibrated before test

8. RF measurement result Good results! Frequency (GHz) S-parameter (dB)
Good results!

9. Diffusion bonding test
Bonding temperature : 1040 °C
Time : 1h 30m
Atmosphere : H2
Prototype disks for PSI accelerating structures
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
Stack no.1
Stack no.2 with 1 insert for test validation process of bonding or brazing.

10. Chemical cleaning procedure
Degreasing with detergent NGL 17.4 spec. ALU III and ultrasound
Deoxidation
with HCl acid
Etching with SLAC solution
Final rinsing with demineralised water and ultrasound
Dry with nitrogen gas
Dry with oven
With M.Balabaila

11. Vacuum before H2 injection for diffusion bonding
Bodycote
Root pump 10-3 torr
Primary pump 10-1 torr
Diffusion pump 10-6 torr

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

13. Cool down Cooling system is composed of water cooling and air cooling.
Water spray
Because of water spray and cooling turbine, the temperature can be reduced rapidly.
Cooling turbine
Air tank

14. Diffusion bonding no.1 weight of 16 Kg Vacuum  H2  Heat up to 1040 C
CERAMICS
4 temperature probes
(thermo-couples) in tuning holes
Furnace warm up and clean up ceramics and support before bonding.
Bonding process 1:30h

15. Diffusion bonding no.2 weight of 16 Kg CERAMICS 2 temperature probes
(thermo-couples)
Furnace warm up and clean up before bonding.
Bonding process 1:30h

16. Stacks after Bonding
Stack no.1
Stack no.2 with 1 insert

17. Metallographical observation
M. Aicheler
Metallographical observation
Bonding no.1
SOI 6
SOI 5
SOI 1
SOI 2
SOI 7
SOI 4
Stack no.1 after cutting
Contact reference line

18. Metallographical observation
M. Aicheler
Metallographical observation
Bonding no.2 5 4 3 2 1
SOI 6
SOI 7
SOI 5
SOI 1
SOI 2
SOI 3
Stack no.2 after cutting
Installed insert before bonding process after cutting

19. Stack no.2 metallographic observation
Joint no. 4
Joint no. 5
Grain crossing
Grain crossing
Contact reference line
Designed contact zone
Designed contact zone
M. Aicheler

20. Conclusion RF flanges + straight waveguides Bonding tests
Vacuum leak 3.6× mbar·l/s (< )( Good)
RF reflection about -30 dB (Good)
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.