SRF2013 - List of Authors (Yang, Q.G.)

Paper	Title	Page
TUP084	Reciprocal Space XRD Mapping with Varied Incident Angle as a Probe of Structure Variation within Surface Depth	651
	X. Zhao JLab, Newport News, Virginia, USA M. Krishnan AASC, San Leandro, California, USA C.E. Reece JLAB, Newport News, Virginia, USA F. Williams, Q.G. Yang NSU, Norfolk, USA
	Funding: This research is supported at AASC by DOE via Grant No. DE-FG02-08ER85162 and Grant No. DE-SC0004994 and by Jefferson Science Associates, LLC under U.S. DOE Contract No. DEAC05- 06OR23177 In this study, we used a differential-depth X-Ray diffraction Reciprocal Spacing Mapping (XRD RSM) technique to investigate the crystal quality of a variety of SRF-relevant Nb film and bulk materials. By choosing different X-ray probing depths, the RSM study successfully revealed the materials’ microstructure evolutions after different materials processes, such as energetic condensation or surface polishing. The RSM data clearly measured the materials’ crystal quality at different thickness. Through a novel differential-depth RSM technique, this study found: I. for a heteroepitaxy Nb film Nb(100)/MgO(100), the film thickening process, via a cathodic arc-discharge Nb ion deposition, created a near-perfect single crystal Nb on the surface’s top-layer; II. for a mechanic polished single-crystal bulk Nb material, the microstructure on the top surface layer is more disordered than that in-grain.

TUP088	NbTiN Based SIS Multilayer Structures for SRF Applications	670
	A-M. Valente-Feliciano, G.V. Eremeev, H.L. Phillips, C.E. Reece JLAB, Newport News, Virginia, USA A.D. Batchelor NCSU AIF, Raleigh, North Carolina, USA R.A. Lukaszew The College of William and Mary, Williamsburg, USA J.K. Spradlin JLab, Newport News, Virginia, USA Q.G. Yang NSU, Norfolk, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. For the past three decades, bulk niobium has been the material of choice for SRF cavities applications. RF cavity performance is now approaching the theoretical limit for bulk niobium. For further improvement of RF cavity performance for future accelerator projects, Superconductor-Insulator-Superconductor (SIS) multilayer structures (as recently proposed by Alex Gurevich) present the theoretical prospect to reach RF performance beyond bulk Nb, using thinly layered higher-Tc superconductors with enhanced Hc1. Jefferson Lab (JLab) is pursuing this approach with the development of NbTiN and AlN based multilayer SIS structures via magnetron sputtering and High Power Impulse Magnetron Sputtering (HiPIMS). This paper presents the results on the characteristics of NbTiN and insulator films and the first RF measurements on NbTiN-based multilayer structure on thick Nb films.

Paper

Title

Page

Reciprocal Space XRD Mapping with Varied Incident Angle as a Probe of Structure Variation within Surface Depth

651

X. Zhao
JLab, Newport News, Virginia, USA
M. Krishnan
AASC, San Leandro, California, USA
C.E. Reece
JLAB, Newport News, Virginia, USA
F. Williams, Q.G. Yang
NSU, Norfolk, USA

Funding: This research is supported at AASC by DOE via Grant No. DE-FG02-08ER85162 and Grant No. DE-SC0004994 and by Jefferson Science Associates, LLC under U.S. DOE Contract No. DEAC05- 06OR23177
In this study, we used a differential-depth X-Ray diffraction Reciprocal Spacing Mapping (XRD RSM) technique to investigate the crystal quality of a variety of SRF-relevant Nb film and bulk materials. By choosing different X-ray probing depths, the RSM study successfully revealed the materials’ microstructure evolutions after different materials processes, such as energetic condensation or surface polishing. The RSM data clearly measured the materials’ crystal quality at different thickness. Through a novel differential-depth RSM technique, this study found: I. for a heteroepitaxy Nb film Nb(100)/MgO(100), the film thickening process, via a cathodic arc-discharge Nb ion deposition, created a near-perfect single crystal Nb on the surface’s top-layer; II. for a mechanic polished single-crystal bulk Nb material, the microstructure on the top surface layer is more disordered than that in-grain.

TUP088

NbTiN Based SIS Multilayer Structures for SRF Applications

670

A-M. Valente-Feliciano, G.V. Eremeev, H.L. Phillips, C.E. Reece
JLAB, Newport News, Virginia, USA
A.D. Batchelor
NCSU AIF, Raleigh, North Carolina, USA
R.A. Lukaszew
The College of William and Mary, Williamsburg, USA
J.K. Spradlin
JLab, Newport News, Virginia, USA
Q.G. Yang
NSU, Norfolk, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
For the past three decades, bulk niobium has been the material of choice for SRF cavities applications. RF cavity performance is now approaching the theoretical limit for bulk niobium. For further improvement of RF cavity performance for future accelerator projects, Superconductor-Insulator-Superconductor (SIS) multilayer structures (as recently proposed by Alex Gurevich) present the theoretical prospect to reach RF performance beyond bulk Nb, using thinly layered higher-Tc superconductors with enhanced Hc1. Jefferson Lab (JLab) is pursuing this approach with the development of NbTiN and AlN based multilayer SIS structures via magnetron sputtering and High Power Impulse Magnetron Sputtering (HiPIMS). This paper presents the results on the characteristics of NbTiN and insulator films and the first RF measurements on NbTiN-based multilayer structure on thick Nb films.