Measurement of Hc1 in superconducting thin films

N. HABERKORN; L. CIVALE; B. MOECKLY; Y. Y. ZHANG; R. SCHULZE; M. HAWLEY; Q. X. JIA; T. TAJIMA

Chicago

Conferencia; 15th International Conference on RF Superconductivity; 2011

Fermilab

Superconducting ratio frequency (SRF) cavities are the leading technology for particle accelerators. Niobium cavities are the core of many existing accelerators and will used in several future systems currently under construction or design. The performance of Nb Cavities has been continuously improved over many years, but presently this technology is approaching to the fundamental limit set by the superconducting critical field of bulk Nb, around 2000 Oe. Gurevich [Appl. Phys. Lett.  88, 012511 (2006)] suggest that performance (maximum accelerating field) of Nb cavities could be extended by covering the internal walls with a superconductor / insulator multilayer. The central idea is that when the thickness of the superconducting layer is smaller than the penetration depth, a size effect results in an increase of the lower critical field Hc1 where the vortex penetration becomes favorable. In this work we explore the enhancement of the Hc1 on MgB2, Nb, and MoN thin films of different thickness. Preliminary results indicate an enhancement of Hc1 in comparison with bulk values, up to values exceeding those currently achievable in Nb cavities. We also found that the thickness dependence of the Hc1 is consistent with the expectation. These results are very promising for SRF applications.