High Performance SDN WLAN Architecture

Wireless Local Area Network (WLAN) infrastructure is a dominant technology for direct access to the Internet and for cellular mobile data traffic offloading to WLANs. Additionally, the enterprise infrastructure can be used to provide functionality for the Internet of Things and Machine to Machine scenarios. This work is focused on improvements of radio resources control scalability similar to mobile networks via handover between cells. We introduce an improved IEEE 802.11 architecture utilizing Software-Defined Networks (SDNs). The proposed architecture allows communications during device movements without losing a quality of service (QoS). The fast seamless handover with QoS enables efficient usage of radio resources in large networks. Our improvements consist of integrating wireless management to OpenFlow protocol, separating encryption and decryption from an access point. In parallel, this feature as a side effect unloads processing at the Access Points (APs). Finally, the functionality of architecture design and scalability was proven by Colored Petri Nets (CPNs). The second proof of our concept was performed on two scenarios. The first scenario was applied to a delay sensitive use case. The second scenario considers a network congestion in real world conditions. Client’s mobility was integrated into both scenarios. The design was developed to demonstrate SDN WLAN architecture efficiency

Magnetic Field Penetration of Niobium Thin Films Produced by the ARIES Collaboration

Superconducting (SC) thin film coatings on Cu substrates are already widely used as an alternative to bulk Nb SRF structures. Using Cu allows improved thermal stability compared to Nb due to having a greater thermal conductivity. Niobium thin film coatings also reduce the amount of Nb required to produce a cavity. The performance of thin film Nb cavities is not as good as bulk Nb cavities. The H2020 ARIES WP15 collaboration studied the impact of substrate polishing and the effect produced on Nb thin film depositions. Multiple samples were produced from Cu and polished with various techniques. The polished Cu substrates were then coated with a Nb film at partner institutions. These samples were characterised with surface characterisation techniques for film morphology and structure. The SC properties were studied with 2 DC techniques, a vibrating sample magnetometer (VSM) and a magnetic field penetration (MFP) facility. The results conclude that both chemical polishing and electropolishing produce the best DC properties in the MFP facility. A comparison between the VSM and the MFP facility can be made for 10 $\mu$m thick samples, but not for 3 $\mu$m thick samples

Main highlights of ARIES WP15 collaboration

International audienceAn international collaboration of research teams from CEA (France), CERN (Switzerland), INFN/LNL (Italy), HZB and USI (Germany), IEE (Slovakia), RTU (Latvia) and STFC/DL (UK), are working together on better understanding of how to improve the properties of superconducting thin films (ScTF) for RF cavities. The collaboration has been formed as WP15 in the H2020 ARIES project funded by EC. The systematic study of ScTF covers: Cu substrate polishing with different techniques (EP, SUBU, EP+SUBU, tumbling, laser), Nb, NbN, Nb₃Sn and SIS film deposition and characterisation, Laser post deposition treatments, DC magnetisation characterisation, application of all obtained knowledge on polishing, deposition and characterisation, Laser post deposition treatments, DC magnetisation characterisation, application to the QPR samples for testing the films at RF conditions. The preparation, deposition and characterisation of each sample involves 3-5 partners enhancing the capability of each other and resulting in a more complete analysis of each film. The talk will give an overview of the collaborative research and will be an introduction to the detailed talks given by the team members

Progress in European Thin Film Activities

International audienceThin-film cavities with higher Tc superconductors (SC) than Nb promise to move the operating temperature from 2 to 4.5 K with savings 3 orders of magnitude in cryogenic power consumption. Several European labs are coordinating their efforts to obtain a first 1.3 GHz cavity prototype through the I.FAST collaboration and other informal collaborations with CERN and DESY. R&D covers the entire production chain. In particular, new production techniques of seamless Copper and Niobium elliptical cavities via additive manufacturing are studied and evaluated. New acid-free polishing techniques to reduce surface roughness in a more sustainable way such as plasma electropolishing and metallographic polishing have been tested. Optimization of coating parameters of higher Tc SC than Nb (Nb₃Sn, V₃Si, NbTiN) via PVD and multilayer via ALD are on the way. Finally, rapid heat treatments such as Flash Lamp Annealing and Laser Annealing are used to avoid or reduce Cu diffusion in the SC film. The development and characterization of SC coatings is done on planar samples, 6 GHz cavities, choke cavities, QPR and 1.3 GHz cavities. This work presents the progress status of these coordinated efforts