CERN summer school programme 2010 Fabrication and measurement

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

• 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 Machining->Chemical cleaning Cu layer 12 -15 µm Machining->Chemical cleaning-> Ni-plating -> Cu-plating

Brazing of RF flanges with a waveguide Under vacuum • With brazing wire Ag/Cu/Pd at 810 -820 °C (Silver/Copper/Palladium) Structure after brazing (Bodycote)

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

CERN TE/VSC Description of examination Customer: CERN BE/RF LEAK TEST CERTIFICATE Object: RF flanges and straight waveguide Leak detector type: Reference leak rate: Minimum detectable leak rate: Tracer gas: System pressure: Test temperature: Leak test date: 19. 07. 2010 LEYBOLD L 200⁺. 6. 2± 15% × 10⁻⁷mbar×L/s 1× 10⁻¹¹ mbar×L/s Helium 99% 1× 10⁻³ mbar 20 C Examined part Brazing Results Max. measured leak rate: 3. 6× 10 -11 mbar×L/s Good results!

With A. Olyunin RF measurement RF flanges+waveguide RF test flanges 2 ports network analyzer Calibrated before test 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 measurement result Frequency (GHz) 11. 4240 11. 9920 S-parameter (d. B) S 11 S 22 -31. 029 -31. 273 -29. 395 -29. 884 Good results!

Diffusion bonding test Bonding temperature : 1040 °C Time : 1 h 30 m Atmosphere : H 2 Prototype disks for PSI accelerating structures Regular cell disk: 2 -35 Standard cell disk 2 -55 Wake monitor cell disk: 3 -36 Standard cell disk 2 -55 Wake monitor cell disk: 4 -37 Standard cell disk 2 -55 Stack no. 1 Wake monitor dell disk: 5 -40 INSERT 2 Wake monitor cell disk: 8 -43 Regular cell disk: 2 -46 Stack no. 2 with 1 insert for test validation process of bonding or brazing. INSERT 1

Chemical cleaning procedure Degreasing with detergent NGL 17. 4 spec. ALU III and ultrasound Final rinsing with demineralised water and ultrasound Deoxidation with HCl acid Dry with nitrogen gas Etching with SLAC solution Dry with oven With M. Balabaila

Vacuum before H 2 injection for diffusion bonding Bodycote Root pump 10 -3 torr Primary pump 10 -1 torr Diffusion pump 10 -6 torr

Diffusion bonding Heating system made of Molybdenum screens (melting point is 2617. 0 °C): temperature of 1040 °C for the bonding process.

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

Diffusion bonding no. 1 Vacuum H 2 Heat up to 1040 C weight of 16 Kg CERAMICS 4 temperature probes (thermo-couples) in tuning holes Furnace warm up and clean up ceramics and support before bonding. Bonding process 1: 30 h

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: 30 h

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

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 M. Aicheler

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

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

Conclusion RF flanges + straight waveguides • • Vacuum leak 3. 6× 10 -11 mbar·l/s (< 10 -10 )( Good) RF reflection about -30 d. B (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.