Surface Analysis of CLAM steel,EUROFER97 steel and W Irradiated in HT-7 Tokamak

1. Surface Analysis of CLAM steel,EUROFER97 steel and W Irradiated in HT-7 Tokamak Qiang Li1,2 Qunying Huang1 Jinnan Yu3 Jiangang Li1 Yican Wu1 Xiaoxiong He1,2 1 Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui, 230031, CHINA 2 Hefei University of Science and Technology, Hefei, Anhui, 230039, CHINA 3 China Institute of Atomic Energy, Beijing 102413, CHINA

2. OUTLINE • About CLAM steel,EUROFER97 steel and W • Experiment procedure Sample Irradiation experiment Surface analysis • Result and discussion Surface morphology Surface composition • conclusion

3. About CLAM steel,EUROFER97 steel and W • CLAM steel and EUROFER97 steel • low activation ferritic/martensitic steel • Good properties for thermal and neutron irradiation • Being considered as structural material and the first wall material in tokamak

4. About CLAM steel,EUROFER97 steel and W • W • Refractory high-Z material • High melting ponit,low vapor pressure,good thermal conductivity,high temperture strength and sputtering resistance • Being considered as plasma facing components

5. Experiment procedure • Sample • Composition of CLAM steel, EUROFER97 steel( wt％) pure multicrystal tungsten(~99.99% wt) • Size:15*7*1.5 mm • All samples were polished and cleaned with acetone and absolute alcohol,and then were dried by hot air.

6. Experiment procedure • Irradiation experiment • HT-7 tokamak • medium size with limiter, and R=1.22m, a=0.285m, BT≤2.2T • the first wall material is 1Cr18Ni9Ti stainless steel, and the limiter material is graphite coated with SiC

7. Experiment procedure • Sample shelf and its position in HT-7

8. Experiment procedure • Plasma average parameters during experiment center: boundary: Ip =125kA ne=1.5*1019m-3 Te =700eV Ti =450eV All samples were irradiated by 802 shots， total irradiation time is about 1200 seconds

9. Experiment procedure • Surface analysis • Scanning Electron Microscope (SEM) • X-ray Photoelectron Spectroscopy (XPS)

10. Result and discussion • Surface morphology • CLAM

11. Result and discussion • EUROFER97

12. Result and discussion • W

13. Result and discussion • Number and diameter of blisters • it seemly equal for blister number in CLAM steel surface and EUROFER97 steel surface, and most of blister diameter is less than 1μm • the blisters in W surface are very little ,their diameter are more than 1μm

14. Result and discussion • Summary • The surface blisters of CLAM steel and EUROFER97 steel are very dense • The blisters seemly range along line in the suface of two kinds of steels • Blisters are observed in the surface of W • Blisters are not observed in the surface of all samples which are far to center plasma

15. Result and discussion • Surface composition • Si Si peaks are obvious in No.2 samples surface, but it is not obvious for No.1 samples • Other elements No obvious change for No.1 samples and No.2 samples

16. conclusion • Relative to W,CLAM steel and EUROFER97 steel are more easy to blister when irradiated by plasma • low activation ferritic steel can be used as fisrt wall materials when considering its plasma irradiation resistance ability • If select W as the plasma facing materials,such as divertor armor, more deep researchs must be proceeded