High Quality MgB₂/Nb Deposited by HPCVD Method

Abstract:

Niobium with the transition temperature of 9 K is the usual material for TESLA superconducting accelerate cavity. The cavity must work at the temperature range of of 2~1.8 K, which would consume large energy. In addition, the low upper critical field is one of reasons causing the problem of accelerate cavities Q-slop. Comparing with Nb material, MgB₂ has several advantages in this application, such as higher Tc of ~39 K, higher upper critical field and the possible lower microwave loss, which would help increasing accelerating gradient and saving operation cost. Because of these benefit, more and more focus is put on this style of accelerating cavity, MgB₂-thick-film/metal-cavity-body. Using Hybrid Physical-Chemical Vapor Deposition method, the micronmeter-thick MgB₂ film on Nb substrate was prepared in the present investigation. The experimental results showed that Tc(0) reached 38.5 K and the Hc₂ was about 20 T. In order to test the films fracture toughness the film as the inner surface was bended. It was found that at small bending angle the influence on the superconducting properties was little. When the bend radius increased to 5 mm, some cracks smaller than 1 micron occured on the film surface. However, the film still attached to the Nb substrate and the Tc was as high as ~33.5 K, showing that the MgB₂ film fabricated by HPCVD had a good compact state with the Nb substrate and good mechanical toughness. These results indicate that the clean MgB₂ thick film has a better feature in the application of superconducting accelerate cavity.

• Periodical: Materials Science Forum (Volumes 745-746)
• Pages: 203-207
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.745-746.203
• Online since: February 2013
• Authors: Li Ping Chen, Fa He, Chen Zhang, Yan Zhang, Yi Ling Chen, Qing Rong Feng, Zi Zhao Gan
• Keywords: MgB₂, Superconducting Accelerator

References

[1] J.K. Hao, K. Zhao, Recent progresses on RF superconductivity. High Power Laser and Particle Beams 17(1) (2005) 1096-1100.

[2] J. Liu, T. Shu and J. Zhang, Research development on free electron laser in Europe, Laser & Optoelectronics Progress 44(6) (2007) 43-47.

[3] S.L. Huang, J.J. Zhuang, K. Zhao, J.E. Cheng, Initial design considerations of PKU-FEL, High Power Laser and Particle Beams 15(1) (2003) 26-29.

[4] M.Q. Ge, S.C. Zhao, H. Sun and J. Gao, Design study on 1. 3 GHz mono-cell high gradient low loss superconducting cavity, High. Energ. Phys. Nuc. 30(4) (2006) 354-358.

[5] T. Tajima, A. Canabal, Y. Zhao, A. Romanenko, B.H. Mocekly, C.D. Nantista, S. Tantawi, L. Phillips, Y. Iwashita and I.E. Campisi, MgB2 for application to RF cavities for accelerators. IEEE Trans. Appl. Supercond. 17 (2) (2007) 1330-1333.

DOI: 10.1109/tasc.2007.899876

[6] F. He, D.T. Xie, Q.R. Feng and K.X. Liu, MgB2 films fabricated on molybdenum substrate by hybrid physical-chemical vapor deposition for superconducting RF cavity applications, Supercond. Sci. Technol. 25 (2012) 065003.

DOI: 10.1088/0953-2048/25/6/065003

[7] X.X. Xi, MgB2 thin film, Supercond. Sci. Technol. 22 (2009) 0403001.

[8] T. Tajima, A. Canabal, Y. Zhao, A. Romanenko, C. Nantista, S. Tantawi, L. Phillips, Y. Iwashita, I. Campisi, B. Moeckly: tests on MgB2 for application to SRF cavities, 2006 Proc. 10th European Particle Accelerator Conf. (Edinburgh, UK).

DOI: 10.1109/tasc.2007.899876

[9] T. Tajima, Possibility of MgB2 application to superconducting cavities, 2002 Proc. 8th European Particle Accelerator Conf. (Paris, June).

[10] M.M. Farahani, F. Attia and K. Salama, hydrogen embrittlement in single- and poly-crystal niobium, Metall. Mater. Trans. A12(4) (1981) 631-638.

DOI: 10.1007/bf02649738