SRF2011 - List of Authors (Zhuang, C.G.)

Paper	Title	Page
THPO045	MgB2 Nonlinear Properties Investigated Under Localized High RF Magnetic Field Excitation	826
	T.M. Tai, B.G. Ghamsari CNAM, UMD, College Park, USA S. M. Anlage UMD, College Park, Maryland, USA X. Xi, C.G. Zhuang TU, Philadelphia, USA
	Funding: We acknowledge the support of DOE/HEP under contract # DESC0004950. In order to increase the accelerating gradient of Superconducting Radio Frequency (SRF) cavities, Magnesium Diboride (MgB2) opens up hope because of its high transition temperature and low surface resistance in the high RF field regime. However, due to the presence of the small superconducting gap in the p band, the nonlinear response of MgB2 is potentially quite large compared to a single gap s-wave superconductor such as Nb. Understanding the mechanisms of nonlinearity coming from the two band structure of MgB2 is an urgent requirement. A localized and strong RF magnetic field, created by a magnetic write head, is integrated into our nonlinear-Meissner-effect scanning microwave microscope [1]. Several MgB2 films (thickness 50 nm, 140 nm), fabricated by a hybrid physical-chemical vapor deposition technique on dielectric substrates, are measured at a fixed location and show a strongly temperature-dependent third harmonic response. We propose that at least two mechanisms are responsible for this nonlinear response, one of which involves vortex nucleation and penetration into the film. [1] Tamin Tai, et al., “Nonlinear Near-Field Microwave Microscope For RF Defect Localization in Superconductors,” IEEE Trans. Appl. Supercond. 21, 2615-2618 (2011).

Paper

Title

Page

MgB2 Nonlinear Properties Investigated Under Localized High RF Magnetic Field Excitation

826

T.M. Tai, B.G. Ghamsari
CNAM, UMD, College Park, USA
S. M. Anlage
UMD, College Park, Maryland, USA
X. Xi, C.G. Zhuang
TU, Philadelphia, USA

Funding: We acknowledge the support of DOE/HEP under contract # DESC0004950.
In order to increase the accelerating gradient of Superconducting Radio Frequency (SRF) cavities, Magnesium Diboride (MgB2) opens up hope because of its high transition temperature and low surface resistance in the high RF field regime. However, due to the presence of the small superconducting gap in the p band, the nonlinear response of MgB2 is potentially quite large compared to a single gap s-wave superconductor such as Nb. Understanding the mechanisms of nonlinearity coming from the two band structure of MgB2 is an urgent requirement. A localized and strong RF magnetic field, created by a magnetic write head, is integrated into our nonlinear-Meissner-effect scanning microwave microscope [1]. Several MgB2 films (thickness 50 nm, 140 nm), fabricated by a hybrid physical-chemical vapor deposition technique on dielectric substrates, are measured at a fixed location and show a strongly temperature-dependent third harmonic response. We propose that at least two mechanisms are responsible for this nonlinear response, one of which involves vortex nucleation and penetration into the film.
[1] Tamin Tai, et al., “Nonlinear Near-Field Microwave Microscope For RF Defect Localization in Superconductors,” IEEE Trans. Appl. Supercond. 21, 2615-2618 (2011).