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16 results on '"Bouat, S."'

4. Epitaxial growth of sputtered ultra-thin NbN layers and junctions on sapphire

Author

Villegier, J.-C., Bouat, S., Cavalier, P., Setzu, R., Espiau de Lamaestre, R., Jorel, C., Odier, P., Guillet, B., Mechin, L., Chauvat, M.P., and Ruterana, P.

Subjects
Magnesium oxide -- Electric properties, Magnesium oxide -- Magnetic properties, Niobium -- Electric properties, Niobium -- Magnetic properties, Sapphires -- Electric properties, Sputtering (Physics) -- Usage, Business, Electronics, Electronics and electrical industries
Published
2009

6. Characterization of superconducting nanometric multilayer samples for SRF applications: first evidence of magnetic screening effect

Author

Antoine, C Z, Berry, S, Bouat, S, Jacquot, J-F, Villegier, J-C, Lamura, G, and Gurevich, A

Subjects
SC RF technology for higher intensity proton accelerators and higher energy electron linacs [10], Accelerators and Storage Rings
Abstract

Best rf bulk niobium accelerating cavities have nearly reached their ultimate limits at rf equatorial magnetic field H ~ 200 mT close to the thermodynamic critical field Hc. In 2006 Gurevich proposed to use nanoscale layers of superconducting materials with high values of Hc > HcNb for magnetic shielding of bulk niobium to increase the breakdown magnetic field of SC rf cavities 1. Depositing good quality layers inside a whole cavity is rather difficult So as a first step, characterization of single layer coating and multilayers was conducted on high quality sputtered samples by applying the technique used for the preparation of superconducting electronics circuits. The samples were characterized by X-ray reflectivity, dc resistivity (PPMS) and dc magnetization (SQUID) measurements. Dc magnetization curves of a 250 nm thick Nb film have been measured, with and without a magnetron sputtered coating of a single or multiple stack of 15 nm MgO and 25 nm NbN layers. The Nb samples with/without the coating exhibit different behaviors and clearly show an enhancement of the magnetic penetration field Because SQUID measurements are influenced by edge and shape effects we propose to develop a specific local magnetic measurement of HC1 based on ac third harmonic analysis in order to reveal the true screening effect of multilayers.

Published
2010

7. Characterization of superconducting multilayers samples

Author

Antoine, C Z, Aguilal, A, Berry, S, Bouat, S, Jacquot, J F, Villegier, J C, Lamura, G, and Gurevich, A

Subjects
SC RF technology for higher intensity proton accelerators and higher energy electron linacs [10], Accelerators and Storage Rings
Abstract

Best RF bulk niobium accelerating cavities have nearly reached their ultimate limits at rf equatorial magnetic field H  200 mT close to the thermodynamic critical field Hc. In 2006 Gurevich proposed to use nanoscale layers of superconducting materials with high values of Hc > HcNb for magnetic shielding of bulk niobium to increase the breakdown magnetic field inside SC RF cavities [1]. Depositing good quality layers inside a whole cavity is rather difficult but we have sputtered high quality samples by applying the technique used for the preparation of superconducting electronics circuits and characterized these samples by X-ray reflectivity, dc resistivity (PPMS) and dc magnetization (SQUID). Dc magnetization curves of a 250 nm thick Nb film have been measured, with and without a magnetron sputtered coating of a single or multiple stack of 15 nm MgO and 25 nm NbN layers. The Nb samples with/without the coating clearly exhibit different behaviors. Because SQUID measurements are influenced by edge and shape effects we propose to develop a specific local magnetic measurement of HC1 based on ac third harmonic analysis in order to reveal the screening effect of multilayers.

Published
2009

15. Thermal stability of sputtered Ni"8"1Fe"1"9/Ag multilayers

Author

Bouat, S., Auffret, S., and Rodmacq, B.

Abstract

From the observation of magnetic and structural properties of Ag/Ni"8"1Fe"1"9 multilayers, we show that two diffusion mechanisms are involved in the thermal evolution of such structures: the diffusion of Ag at interfaces and at grain boundaries. Upon annealing, they first lead to a decrease in interface roughness and then cause the layers to become discontinuous. We have also observed that thermal treatments under an applied magnetic field have an influence on the magnetoresistive properties of the samples. This could be due to some modification of the domain structure, resulting in a different contribution of electron scattering by domains walls.

Published
1997
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16. Frequency scaling with miniature COmpact MIcrowave and Coaxial ion sources.

Author

Sortais P, André T, Angot J, Bouat S, Jacob J, Lamy T, and Sole P

Abstract

We will present recent basic developments about possible extension of the COMIC (for COmpact MIcrowave and Coaxial) devices up to 5.8 GHz in place of the present 2.45 GHz operation [P. Sortais, T. Lamy, J. Médard, J. Angot, L. Latrasse, and T. Thuillier, Rev. Sci. Instrum. 81, 02B314 (2010)]. New applications associating multiple COMIC devices for thin film deposition will be described and we will explain why an increase of the current density delivered by each individual ion source could lead to the increase of the deposition rate. For this purpose, we will present results of about two devices working at 5.8 GHz. The first one is a tiny ion source, the world smallest microwave ion source, exactly similar to COMIC but operating at 5.8 GHz with a quarter wave cavity structure and a few watts microwave power consumption. We will show that the frequency scaling effect is effective inside such small machines. The second one is a more ambitious ion source designed around a three quarter wave structure that works with a few tens of watts at 5.8 GHz.

Published
2014
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