SRF2011 - List of Authors (Berry, S.)

Paper	Title	Page
TUIOA03	Magnetic Screening of NbN Multilayers Samples	281
	C.Z. Antoine, S. Berry CEA/DSM/IRFU, France A. Andreone Naples University Federico II, Napoli, Italy Q. Famery, J. Leclerc CEA/IRFU, Gif-sur-Yvette, France G. Lamura CNR-INFM-LAMIA, Genova, Italy J.C. Villegier CEA/INAC, Grenoble Cedex 9, France
	In 2006 Gurevich proposed to use nanoscale layers of superconducting materials with high values of Hc > Hc (Nb) for magnetic shielding of bulk niobium to increase the field in Nb RF cavities. We have deposited high quality “model” samples on monocrystalline sapphire substrates. A 250 nm layer of niobium figures the bulk Nb. It was coated with a single or multiple stacks of NbN layers (25 nm or 12 nm) separated by 15 nm MgO barriers, and characterized by X-rays reflectivity and DC transport measurements. DC or AC measurement of HC1 is an important tool for multilayers evaluation during the sample optimization phase. A clear increase of HC1 at low frequency is a promising indication since HC1 is expected to be higher in RF. We have measured the first magnetic penetration field HP (~ HC1) on DC magnetization curves in a SQUID system. HP of NbN covered samples is increased compared to Nb alone. We have also developed a set-up that allows measuring HC1 over a large range of field and temperature with a local probe method based on 3rd harmonic analysis. We have confirmed the screening behavior of a single 25 nm NbN layer placed on the top of a thick Nb layer.

Paper

Title

Page

Magnetic Screening of NbN Multilayers Samples

281

C.Z. Antoine, S. Berry
CEA/DSM/IRFU, France
A. Andreone
Naples University Federico II, Napoli, Italy
Q. Famery, J. Leclerc
CEA/IRFU, Gif-sur-Yvette, France
G. Lamura
CNR-INFM-LAMIA, Genova, Italy
J.C. Villegier
CEA/INAC, Grenoble Cedex 9, France

In 2006 Gurevich proposed to use nanoscale layers of superconducting materials with high values of Hc > Hc (Nb) for magnetic shielding of bulk niobium to increase the field in Nb RF cavities. We have deposited high quality “model” samples on monocrystalline sapphire substrates. A 250 nm layer of niobium figures the bulk Nb. It was coated with a single or multiple stacks of NbN layers (25 nm or 12 nm) separated by 15 nm MgO barriers, and characterized by X-rays reflectivity and DC transport measurements. DC or AC measurement of HC1 is an important tool for multilayers evaluation during the sample optimization phase. A clear increase of HC1 at low frequency is a promising indication since HC1 is expected to be higher in RF. We have measured the first magnetic penetration field HP (~ HC1) on DC magnetization curves in a SQUID system. HP of NbN covered samples is increased compared to Nb alone. We have also developed a set-up that allows measuring HC1 over a large range of field and temperature with a local probe method based on 3rd harmonic analysis. We have confirmed the screening behavior of a single 25 nm NbN layer placed on the top of a thick Nb layer.