Conditionnement des coupleurs de puissance HF pour cavités supraconductrices en mode pulsé

Groupe SERAL'accélérateur de laser à électron libre XFEL utilise des cavités supraconductrices en mode pulsé fonctionnant sous un champ électrique supérieur à 20 MV/m à 1.3GHz [1]. Les coupleurs de puissance HF TTF-III, destinés pour cette machine, doivent assurer un transfert de puissance HF de 150 kW vers les cavités et peuvent supporter des pics de puissance allant jusqu'à 1 MW. Cette fonction ne peut être garantie qu'après un conditionnement à température ambiante de ces coupleurs, consistant à l'adaptation progressive du coupleur à supporter les champs électriques créés par le passage de la puissance HF. Un stand de tests a été installé au Laboratoire de l'Accélérateur Linéaire pour conditionner et tester les performances des coupleurs avant leur mise sur cavité. Une automatisation de ce stand a été réalisée permettant une meilleure gestion du contrôle/commande de ces opérations ainsi qu'un taux d'acquisition de données important pour analyser le comportement des coupleurs

Preparation And Conditioning Of The TTF VUV-FEL Power Couplers

http://www.lns.cornell.edu/public/SRF2005/pdfs/ThP48.pdfInternational audienceRecent advances in accelerator technology have permitted the manufacture of superconducting (SC) cavities with high gradients (> 30 MV/m). One ambitious aim now consists in making them operational in accelerator facilities (correctly matched to the RF source, preserve the cavity vacuum, cavity cleanliness and operating temperature conditions). The input power couplers have a crucial role in achieving all of these functions. Therefore, the input power couplers for these cavities are carefully designed and then prepared under very strict conditions. RF conditioning of input power couplers at room temperature is an important step in their preparation before mounting them on cavities. It allows one to test the robustness of the coupler, condition away residual absorbed gases and “burn-off” microscopic surface imperfections. The conditioning of the TTF-III couplers (for the TTF VUV-FEL accelerator at DESY) is an ideal occasion to learn about their properties and behaviour and to asses their suitability for the ILC, which will use cold RF technology. We will present the status of processing the TTF-III couplers at LAL-Orsay, an activity performed in close collaboration with DESY-Hamburg

Properties Analysis of Inconsistency-based Possibilistic Similarity Measures

International audienceThis paper deals with the problem of measuring the similarity degree between two normalized possibility distributions encoding preferences or uncertain knowledge. Many exist- ing de nitions of possibilistic similarity indexes aggregate pairwise distances between each situation in possibility distributions. This paper goes one step further, and discusses de nitions of possibilistic similarity measures that include inconsistency degrees between possibility distribu- tions. In particular, we propose a postulate-based analysis of similarity indexes which extends the basic ones that have been recently proposed in a literature

Stromal cell-derived factor 1 polymorphism in patients infected with HIV and implications for AIDS progression in Tunisia

Sameh Amara1, Jorge Domenech2, Faouzi Jenhani31Cellular Immunology and Cytometry, National Blood Transfusion Center, Tunis, Tunisia; 2Hematopoiesis Laboratory, Faculty of Medicine, University of Tours, Tours, France; 3Faculty of Pharmacy, Unit Research in Immunology, Tunis, TunisiaBackground: An interesting finding in the epidemiology of human immunodeficiency virus (HIV) infection is that certain mutations in genes coding for chemokines, and their receptors and ligands, may confer resistance or susceptibility to HIV-1 infection and acquired immunodeficiency syndrome (AIDS) progression. The mutation most frequently studied is stromal cell-derived factor (SDF)1-3'A, a single nucleotide polymorphism in the 3' untranslated region at the 801 position of the SDF1 gene, which seems to be associated with susceptibility or resistance to diseases, including AIDS. We examined the frequency of the above polymorphisms in the Tunisian population, and evaluated their contribution to a protective genetic background against HIV infection and progression.Methods and materials: One hundred forty blood samples from HIV-infected patients from the Cellular Immunology Research Laboratory at the National Blood Transfusion Center were compared with those of 164 random blood donors from the same center. Genotyping was initially performed by polymerase chain reaction (PCR) analysis. SDF1 PCR product genomic regions were further subjected to restriction fragment length polymorphism analysis for genotype determination. Screening for the SDF1 polymorphism in the HIV-infected population yielded 56 heterozygous (40%), 52 mutation homozygous (37.1%), and 32 wild-type homozygous (22.8%) subjects. In contrast, in our healthy population, we found 70/164 heterozygous (42.6%), nine mutation homozygous (5.4%), and 85 wild-type homozygous (51.8%) subjects. The allele frequencies in the HIV-infected and healthy populations were f(SD1 3'A) = 57.1%, f(SDF1) = 42.8%, f(SDF1 3'A) = 26.8%, and f(SDF1) = 73.1%, respectively. The allelic and genotypic frequencies of the SDF1 3'A in our population show significantly higher distribution profiles compared with those observed in other Caucasian, European, and African American populations. Our results were examined by X2 test and appear to confirm an association between polymorphism and AIDS progression. A higher odds ratio (>1) was found for the SDF1-3'A allele than for the wild-type allele (<1).Conclusion: This result seems to confirm that the SDF1-3'A allele is associated with acceleration and progression from HIV infection to AIDS in the Tunisian population.Keywords: human immunodeficiency virus, SDF1 polymorphism, Tunisi

Titanium Nitride Coating as a Multipactor Suppressor on RF Coupler Ceramic Windows

International audienceLAL-Orsay is developing an important effort on R&D studies on RF power couplers. One of the most critical components of those devices is the ceramic RF window that allows the power flux to be injected in the coaxial line. The presence of a dielectric window on a high power RF line has a strong influence on the multipactor phenomena. To reduce this effect, the decrease the secondary emission yield (SEY)of the ceramic window is needed. Due to its low SEY coefficient, TiN coating is used for this goal. In this framework, a TiN sputtering bench has been developed in LAL. The reactive sputtering of TiN needs the optimisation of gas flow parameters and electrical one, to obtain stoechiometric deposit. XRD analysis was performed to control the film composition and stoechiometry. Measurements point out how the Nitrogen vacancy on the film can be controlled acting on the N2 flow. In addition, the coating thickness must be optimized so that the TiN coating effectively reduces the SEY coefficient but does not cause excessive heating, due to ohmic loss. For this purposes, multipactor level breakdown and resistance measurements were done for different deposit thickness

SemCoTrip: a variety-seeking model for recommending travel activities in a composite trip

Selecting appropriate activities, especially in multi-destinations trips, is a hard task that many travellers face each time they want to plan for a trip. With the budget and time limitations, travellers will try to select activities that best fit their personal interests. Most of existing travel recommender systems don't focus on activities that a traveller might be interested in. In this paper, we go beyond the specific problem of combining regions in a composite trip to propose a variety-seeking model which is capable of providing travelllers with recommendations on what activities they can engage in when visiting different regions. A semantical hierarchical clustering-based model is proposed to guarantee diversity within the set of recommended activities. Experimental results on a real dataset have shown that the proposed approach helps the traveller to avoid doing the same or similar activities in a composite trip, thus, promoting less popular activities to be selected

Developments in Conditioning Procedures for the TTF-III Power Couplers

JACoW web site http://accelconf.web.cern.ch/AccelConf/e06/Despite extensive experience in many laboratories on power conditioning of couplers for RF superconducting accelerators, it is still not a well understood procedure and can produce many unpredictable phenomena. There remains considerable interest in reducing the power coupler conditioning time necessary for superconducting linear accelerators. This paper presents studies of optimisation of the conditioning procedure for the couplers intended for use on the European XFEL project

Tunisian reservoirs : diagnosis and biological potentialities

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