1. Samuli Heikkinen TS-MME-MM CLIC RF meeting 30 July 2008 High fatigue-strength options for brazed structures

2. Samuli Heikkinen TS-MME-MM CLIC RF meeting 30 July 2008 High fatigue-strength options for brazed structures Fatigue resistance MachinabilityElevated temperatures Breakdown resistance Oxygen-free copper C10100 -+- ? tests under way + Copper zirconium C15000 ++ - ? to be confirmed + tests under way GlidCop® Al-15 +- tests underway +? to be confirmed Samuli Heikkinen, CLIC meeting 22.2.2008 + To be confirmed - -

3. Samuli Heikkinen TS-MME-MM CLIC RF meeting 30 July 2008 High fatigue-strength options for brazed structures Higher strength is generally achieved by blocking the dislocation motion Dislocations can block the movement of each others if the dislocation density is high Cold working increases the dislocation density Impurities can block the dislocation motion  alloying Cu-OFE Cold worked material has high dislocation density. Elevated temperatures (>150°C) decrease the dislocation density and result in a softer material. Grain size has only a secondary effect. For annealed copper smaller grain size can increase the strength by blocking the dislocations moving freely in the grain. For cold worked copper the difference is not significant. cw σ Small grain size High grain size Cu-Zr Cold worked material has high dislocation density and aged material has high density 2.6*10²³ 1/m³ of small 1-4 nm Cu5Zr precipitates (average spacing 16 nm). Elevated temperatures (700°C) “overage” the material  decrease Cu5Zr precipitate density to 0.7*10²¹ 1/m³ and increase their size to 40 nm (average spacing 113 nm)  softer material. Small grain size is typically 50-100 µm.Dislocation density can be for copper 10¹² 1/cm² (spacing 10 nm) Heated layer of CLIC structures is about 20 µm. Cw + aging σ 0 0 GlidCop Cold worked and material has high dislocation density. GlidCop has “naturally” high density 1*10²² 1/m³ of small 7 nm Al2O3 particles (average spacing 46 nm). Elevated temperatures does not modify the Al2O3 particles. Dislocation density decreases and the material becomes slightly softer. Cw + aging σ 0

4. Samuli Heikkinen TS-MME-MM CLIC RF meeting 30 July 2008 High fatigue-strength options for brazed structures Tensile strengths [MPa]

5. Samuli Heikkinen TS-MME-MM CLIC RF meeting 30 July 2008 High fatigue-strength options for brazed structures Fatigue strengths [MPa] (CLIC lifetime values) Mechanical fatigue Criteria: crack RF fatigue Criteria: visually observed damage (RF still happy) CLIC limit 56ºC planned

6. Samuli Heikkinen TS-MME-MM CLIC RF meeting 30 July 2008 High fatigue-strength options for brazed structures The end / spares

7. Samuli Heikkinen TS-MME-MM CLIC RF meeting 30 July 2008 High fatigue-strength options for brazed structures RF Laser RF Ultrasound Cu-OFE (C10100), CuZr (C15000), GlidCop Al-15 Candidates: Cu-OFE (C10100), CuZr (C15000), GlidCop Al-15

8. Samuli Heikkinen TS-MME-MM CLIC RF meeting 30 July 2008 High fatigue-strength options for brazed structures Cu-OFE_1 (ΔT ~ 70ºC) after N=2*10^6 Cu-OFE_2 (ΔT ~ 110ºC) after N=2*10^6 Fatigued zone RF breakdown zones 110ºC 70ºC Fatigue by RF experiments Cu-OFE_2 (ΔT ~ 70ºC) after N=10^7 CuZr_2 (ΔT ~ 70ºC) after N=10^7 CuZr_1 (ΔT ~ 100ºC) after N=10^7 No change in RF performance was observed during the runs! “soft” CuZr!