Presented by H. Li 1 J.L. Chen 1 , J.G. Li 1 , Z.X. Li 2 lhua@ipp.ac

1. High heat load properties of actively cooled tungsten/copper mock-ups joining by explosive compound Presented byH. Li1 J.L. Chen1, J.G. Li1, Z.X. Li2 lhua@ipp.ac.cn 1. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, P.R.China 2. Northwest Institute for Non-ferrous Metal Research, Xi’ an710016, P.R.China

2. Outline • Motivation • Mock-ups and experiments • ---- Mock-ups, Tungsten(2mm) as PFM , CuCr alloy as heat sink , explosive compound • ---- Electron high heat flux experiments high heat load limit test; heat transfer properties ---- Numerical Simulation • ---- Microstructure analysis • Results and discussion • Conclusions

3. Motivations • Tungsten, candidate of PFM • High melting point, Low erosion, low tritium retention etc., • Copper alloy, heat sink material • High conductivity, high strength at elevated temp.(CuCrZr) • Disadvantages in joining technique • Large differences in CTEs and elastic modulus resulting in high stress. • Structure reliability and lifetime in cycling operation. • W/CuCr mock-ups joining by explosive compound Developed and manufactured for EAST in ASIPP.

4. Mock-ups W plate with 2mm thickness by forging A, 30*60mm B, 30*30mm

5. 2mm 6mm 10mm Cooling conditions 3mm Pressure 0.3MPa Temperature 300C Flow rate 3m3/s Heat load conditions Heat flux 1~10MW/m2 Cross-sectional view of the mock-up

6. Electron beam facility

7. Heat load limit test • Joint temp. reached about 4700C and then rising rapidly. • One side of the mock-up appeared continuous hot spots and red. • delamination happened. • The heat load limit is 7MW/m2. Mock-up A

8. Microstructure analysis W Delamination Cu • Cracks originated at the edge and then expanded to center, which resulted in delamination. • A larger mumber of cracks appeared at the other side of the copper/filler joint-face after tests. • At high temp.(4700C), high stress and large plastic strain happeded near the copper/filler material joint-face.

9. Mock-up B Heat load properties • Under2, 4MW/m2,good agreement in temp. between tests and simulation, which indicated • good thermal contact and high heat trasfer capability at the joint. • Under6MW/m2, • joint temp. higher than simulation and slightly rising in the end of the heat loading, which meant the thermal contact was not good as that under 4MW/m2. • The cooling time,slightly longer under 6MW/m2 than under other heat flux.

10. Microstructure analysis After tests Before tests • Tungsten/filler joint-face is good before and after heat load. • Before tests(after joining), pores appeared in the filler material. • After heat loads, the cracks appeared near the filler/Cu joint face and reduced the heat transfer capability, which resulted in higher joint temp. • For W/Cu joints, the cracks or faluires often happened near the copper. Avoiding the strength reduction of the copper and improving the filler material’s properties (CTEs, modulus, ductibility, adhesion, etc.) is the key issue.

11. Simulation 6MW/m2 h=6mm • High temp. of the joint-faceunderHeat flux of 6MW/m2 is dangerious for W/Cu joint. • if reducing the distance between the vertex and jointface to 3mm, the temp. of the joint-face (center) decreased from 3600C to 3000C under 6MW/m2 and the mock-up would have more structure reliability.

12. Conclusion • Two mock-ups with forging W plate and CuCr heat sink joining by explosive compund were developed, manufactured and tested. • The heat load limit of the mock-up is 7MW/m2, and delamination happened. But the mock-up can sustain about 6MW/m2 although some cracks happened at the joint face. • If the heat load does not exceed 4MW/m2, the mock-up will have good heat transfer properties and good structure stability. • If reducing the distance between the vertex of the channel and the joint-face from 6mm to 3mm, it is expected that the mock-up has higher reliability due to lower temp. at the joint-face. • The cracks or failures often originated and developed at copper/filler joint-face,especially near the edge. For W/CuCr explosive compund, the properties of filler materials and the adhesion strength are very important to its reliability and lifetime under high heat loading.

13. Thanks