1. Study of MgB 2 Thin Films on Nb by Pulse Laser Deposition S.Mitsunobu, S.Inagaki, H.Nakanishi, M.Wake and M.Fukutomi* KEK,NIMR*

2. Scope of talk Introduction Forming method Mgb2 thin film PLD equipment PLD equipment Precursor annealing Precursor annealing RF Measurement of the MgB2 thin film and Nb Measurement of photo electron from the MgB2 thin film and Nb Summary

3. INTRODUCTION The large efforts have been concentrated on Nb cavities for International Linear Collider (ILC). The maximum accelerating field gradient of Nb cavities is limited about 50 MV/m due to Hcsh. MgB2 have higher Tc than Nb and expected to have higher Hcsh. Thin films of MgB2 on Nb is useful to increase future ILC energy upgrading. At KEK, the preliminary test of thin films on Nb by Pulse Laser Deposition(PLD) method have been started and initially the direct deposition of MgB2 film on Nb was studied.

4. Conceptual Drawing of Pulse Laser Deposition

5. Laser system of PLD

6. Vacuum Chamber of PLD

7. MgB2 Target Substrate

8. PLD Processing

10. Heating 620 o C in 1atom Ar

12. MgB2 film directly formed on Nb of 2.5mm thick

13. Heating 620 o C

14. Q measurement system

15. Cu Cold test cavity

16. Q measurement system

19. Photo electron measurement by PLD system

20. NbMgB2 film on Nb Relative Intensity of Photo electron by 284nm laser wave length

21. Summery MgB2 precursor films formed on Nb by PLD. The precursor film annealed at 620 o C. Cold RF measurement have been done. The film partially superconducting. Preliminary, photo electrons were measured for Nb and MgB2. Some damaging of MgB2 surface was induced by defocused laser beam. More study will be continued.