SRF2011 - List of Authors (Proslier, Th.)

Paper

Title

Page

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]

THPO072

Raman Spectroscopy as a Probe of Surface Oxides and Hydrides on Niobium

912

J. Zasadzinski
IIT, Chicago, Illinois, USA
B. Albee, S. Bishnoi, C. Cao
Illinois Institute of Technology, Chicago, IL, USA
G. Ciovati
JLAB, Newport News, Virginia, USA
L.D. Cooley, D.C. Ford
Fermilab, Batavia, USA
Th. Proslier
ANL, Argonne, USA

Funding: ANL, FNAL
Raman microscopy/spectroscopy has been used in conjunction with AFM, tunneling and magnetic susceptibility to identify surface oxides and hydrides on annealed, recrystallized foils of high purity Nb and on single crystals of cavity grade Nb. Cold worked regions of the Nb foil as well as rough regions near grain boundaries showed clear evidence of ordered hydride phases which were identified by VASP phonon calculations. Cold worked regions also displayed enhanced surface paramagnetism. Surface enhanced Raman spectra have also been obtained using 1.0 nm Au depositon. The SERS spectra reveal hydride molecular species which are not observable by conventional Raman. These results indicate that Raman is a useful probe of Nb surfaces relevant for cavity performance

Paper	Title	Page
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]

THPO072	Raman Spectroscopy as a Probe of Surface Oxides and Hydrides on Niobium	912
	J. Zasadzinski IIT, Chicago, Illinois, USA B. Albee, S. Bishnoi, C. Cao Illinois Institute of Technology, Chicago, IL, USA G. Ciovati JLAB, Newport News, Virginia, USA L.D. Cooley, D.C. Ford Fermilab, Batavia, USA Th. Proslier ANL, Argonne, USA
	Funding: ANL, FNAL Raman microscopy/spectroscopy has been used in conjunction with AFM, tunneling and magnetic susceptibility to identify surface oxides and hydrides on annealed, recrystallized foils of high purity Nb and on single crystals of cavity grade Nb. Cold worked regions of the Nb foil as well as rough regions near grain boundaries showed clear evidence of ordered hydride phases which were identified by VASP phonon calculations. Cold worked regions also displayed enhanced surface paramagnetism. Surface enhanced Raman spectra have also been obtained using 1.0 nm Au depositon. The SERS spectra reveal hydride molecular species which are not observable by conventional Raman. These results indicate that Raman is a useful probe of Nb surfaces relevant for cavity performance