SRF2011 - List of Authors (Yoneda, C.)

Paper

Title

Page

Testing the RF Properties of Novel Super Conducting Materials

325

J. Guo, D.W. Martin, S.G. Tantawi, C. Yoneda
SLAC, Menlo Park, California, USA

Development in niobium SRF cavities has resulted in successful applications among a wide range of particle accelerator projects, due to the combination of its low surface RF resistance and high quenching field. However, new materials with better performance - especially higher quenching magnetic field - are always tempting to accelerator scientist and have attracted enormous research effort. We have developed a testing system capable to characterize both the surface RF resistance and quenching magnetic field of a superconducting material. The system uses a hemispheric resonant cavity with high quality factor and an interchangeable wall, which can host a flat sample with 2-3 inch diameter. Various samples have been tested, including Nb, MgB2 and Cu in different forms. We will present the most recent developments of the system and discuss the testing results.

TUIOA04

MgB2 Thin Film Studies

287

T. Tajima, L. Civale, N.F. Haberkorn, R.K. Schulze
LANL, Los Alamos, New Mexico, USA
V.A. Dolgashev, J. Guo, D.W. Martin, S.G. Tantawi, C. Yoneda
SLAC, Menlo Park, California, USA
H. Inoue, T. Tajima
KEK, Ibaraki, Japan
A. Matsumoto, E. Watanabe
NIMS, Tsukuba, Ibaraki, Japan
B. Moeckly, C. Yung
STI, Santa Barbara, California, USA
M.J. Pellin, Th. Proslier
ANL, Argonne, USA
X. Xi
TU, Philadelphia, USA
B. Xiao
JLAB, Newport News, Virginia, USA

Funding: This work is supported by the DOE Office of Nuclear Physics.
Demonstrating the idea of enhancing achievable surface magnetic field by coating multilayer thin film superconductors proposed by Gurevich is the main objective. DC magnetization measurements of 500 nm and 300 nm MgB2 films coated on Sapphire showed an increase in the lower critical magnetic field (Bc1) compared to that of bulk. Also, the Bc1 of a 300 nm film showed >200 mT at 4.5 K, which is >25 % higher than that of Nb (~145 mT). RF measurements using a 11.4 GHz pulsed Klystron and a TE013-like mode hemispherical copper cavity with a 2-inch (50.8 mm) diameter sample, however, have shown a low quenching field of 42 mT at 4 K. From detailed data analyses together with the data on Nb quench fields these quenches were found to be thermal, not magnetic, due to a high RF resistance caused by inter-diffusion of coated materials at the interfaces. Additionally, recent results of RF surface resistance at 7.5 GHz using a calorimetric technique at JLab will also be shown.

Slides TUIOA04 [1.144 MB]

Paper	Title	Page
TUIOB03	Testing the RF Properties of Novel Super Conducting Materials	325
	J. Guo, D.W. Martin, S.G. Tantawi, C. Yoneda SLAC, Menlo Park, California, USA
	Development in niobium SRF cavities has resulted in successful applications among a wide range of particle accelerator projects, due to the combination of its low surface RF resistance and high quenching field. However, new materials with better performance - especially higher quenching magnetic field - are always tempting to accelerator scientist and have attracted enormous research effort. We have developed a testing system capable to characterize both the surface RF resistance and quenching magnetic field of a superconducting material. The system uses a hemispheric resonant cavity with high quality factor and an interchangeable wall, which can host a flat sample with 2-3 inch diameter. Various samples have been tested, including Nb, MgB2 and Cu in different forms. We will present the most recent developments of the system and discuss the testing results.

TUIOA04	MgB2 Thin Film Studies	287
	T. Tajima, L. Civale, N.F. Haberkorn, R.K. Schulze LANL, Los Alamos, New Mexico, USA V.A. Dolgashev, J. Guo, D.W. Martin, S.G. Tantawi, C. Yoneda SLAC, Menlo Park, California, USA H. Inoue, T. Tajima KEK, Ibaraki, Japan A. Matsumoto, E. Watanabe NIMS, Tsukuba, Ibaraki, Japan B. Moeckly, C. Yung STI, Santa Barbara, California, USA M.J. Pellin, Th. Proslier ANL, Argonne, USA X. Xi TU, Philadelphia, USA B. Xiao JLAB, Newport News, Virginia, USA
	Funding: This work is supported by the DOE Office of Nuclear Physics. Demonstrating the idea of enhancing achievable surface magnetic field by coating multilayer thin film superconductors proposed by Gurevich is the main objective. DC magnetization measurements of 500 nm and 300 nm MgB2 films coated on Sapphire showed an increase in the lower critical magnetic field (Bc1) compared to that of bulk. Also, the Bc1 of a 300 nm film showed >200 mT at 4.5 K, which is >25 % higher than that of Nb (~145 mT). RF measurements using a 11.4 GHz pulsed Klystron and a TE013-like mode hemispherical copper cavity with a 2-inch (50.8 mm) diameter sample, however, have shown a low quenching field of 42 mT at 4 K. From detailed data analyses together with the data on Nb quench fields these quenches were found to be thermal, not magnetic, due to a high RF resistance caused by inter-diffusion of coated materials at the interfaces. Additionally, recent results of RF surface resistance at 7.5 GHz using a calorimetric technique at JLab will also be shown.
	Slides TUIOA04 [1.144 MB]