Lowering the activation temperature of TiZrV non-evaporable getter films

In order to reduce the activation temperature of the TiZrV alloy, thin films of various compositions were produced by three-cathode magnetron sputtering on stainless steel substrates. For the characterisation of the activation behaviour the surface chemical composition has been monitored by Auger Electron Spectroscopy (AES) during specific in situ thermal cycles. The volume elemental composition of the film has been measured by Energy Dispersive X-ray spectroscopy (EDX) and the morphology (crystal structure and size of the crystallites) has been investigated by X-ray diffraction (XRD). The criteria indicating the sample quality and its dependence on film structure and chemical composition are presented and discussed

Ion-stimulated gas desorption yields and their dependence on the surface preparation of stainless steel

Ion-induced gas desorption yields were investigated for 4.2 MeV/u lead ions incident on 316 LN stainless steel surfaces. Focussed on a possible application for the Low Energy Ion Ring (LEIR) vacuum system, the influence of surface treatments like chemical etching, electropolishing and gold-coating on the desorption yields was studied with accelerator-type vacuum chambers. The surface composition of similar prepared samples was investigated with X-ray Photoemission Spectroscopy (XPS). Desorption yields for H2, CH4, CO, Ar and CO2, which are of fundamental interest for LEIR and future accelerator applications, are reported as a function of impact angle, ion dose and charge state (+27, +53) of the lead ion beam

Electron cloud buildup and impedance effects on beam dynamics in the future circular e+e− collider and experimental characterization of thin TiZrV vacuum chamber coatings

The Future Circular Collider FCC-ee is a study toward a high luminosity electron-positron collider with a centre-of-mass energy from 91 GeV to 365 GeV. Due to the beam parameters and pipe dimensions, collective effects and electron cloud can be very critical aspects for the machine and can represent the main limitations to its performance. An estimation of the electron cloud build up in the main machine components and an impedance model are required to analyze the induced instabilities and to find solutions for their mitigation. Special attention has been given to the resistive wall impedance associated with a layer of nonevaporable getter (NEG) coating on the vacuum chamber required for electron cloud mitigation. The studies presented in this paper will show that minimizing the thickness of this coating layer is mandatory to increase the single bunch instability thresholds in the proposed lepton collider at 45.6 GeV. For this reason, NEG thin films with thicknesses below 250 nm have been investigated by means of numerical simulations to minimize the resistive wall impedance. In parallel, an extensive measurement campaign was performed at CERN to characterize these thin films, with the purpose of finding the minimum effective thickness satisfying vacuum and electron cloud requirements

Novel types of anti-ecloud surfaces

In high power RF devices for space, secondary electron emission appears as the main parameter governing the multipactor effect and as well as the e-cloud in large accelerators. Critical experimental activities included development of coatings with low secondary electron emission yield (SEY) for steel (large accelerators) and aluminium (space applications). Coatings with surface roughness of high aspect ratio producing the so-call secondary emission suppression effect appear as the selected strategy. In this work a detailed study of the SEY of these technological coatings and also the experimental deposition methods (PVD and electrochemical) are presented. The coating-design approach selected for new low SEY coatings include rough metals (Ag, Au, Al), rough alloys (NEG), particulated and magnetized surfaces, and also graphene like coatings. It was found that surface roughness also mitigate the SEY deterioration due to aging processes.Comment: 4 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba, Italy; CERN Yellow Report CERN-2013-002, pp.153-15

Role of surface microgeometries on electron escape probability and secondary electron yield of metal surfaces

The influence of microgeometries on the Secondary Electron Yield (SEY) of surfaces is investigated. Laser written structures of different aspect ratio (height to width) on a copper surface tuned the SEY of the surface and reduced its value to less than unity. The aspect ratio of microstructures was methodically controlled by varying the laser parameters. The results obtained corroborate a recent theoretical model of SEY reduction as a function of the aspect ratio of microstructures. Nanostructures - which are formed inside the microstructures during the interaction with the laser beam - provided further reduction in SEY comparable to that obtained in the simulation of structures which were coated with an absorptive layer suppressing secondary electron emission

Influence of the elemental composition and crystal structure on the vacuum properties of Ti-Zr-V non-evaporable getter films

Non-evaporable thin film getters based on the elements of the 4th and 5th columns of the periodic table have been deposited by sputtering. Among the about 20 alloys studied to date, the lowest activation temperature (about 180 °C for a 24-hour heating) has been found for the Ti-Zr-V system in a well-defined composition range. The characterization of the activation behavior of such Ti-Zr-V films is presented. The evolution of the surface chemical composition during activation is monitored by Auger Electron Spectroscopy (AES) and the functional properties are evaluated by pumping speed measurements. The pumping speed characteristics are quite similar to those already measured for commercially available NEG materials, except for the much lower saturation coverage for CO. This inconvenience, which is due to the smooth surface structure of these films, can be counteracted by increasing the roughness of the substrate

Out of focus ultrafast processing of metals for reduced secondary electron yield

We have demonstrated out-of-focus ultrafast pulsed laser processing of copper with a variable working distance, without the need for mechanical movement. This was achieved by employing a diffractive optical element. The method has been demonstrated in a practical application to reduce the secondary electron yield (SEY) of copper to below 1.3. We show that using an extended focus element not only increases the consistency of processing across a range of working distances, but also changes the topography of the produced structures, reducing the SEY. This presented approach shows promise in facilitating the Large Hadron Collider’s (LHC’s) upcoming high luminosity upgrade by preventing electron clouds

Increased cancer risk in patients undergoing dialysis: a population-based cohort study in North-Eastern Italy

open116noBACKGROUND: In southern Europe, the risk of cancer in patients with end-stage kidney disease receiving dialysis has not been well quantified. The aim of this study was to assess the overall pattern of risk for de novo malignancies (DNMs) among dialysis patients in the Friuli Venezia Giulia region, north-eastern Italy. METHODS: A population-based cohort study among 3407 dialysis patients was conducted through a record linkage between local healthcare databases and the cancer registry (1998-2013). Person-years (PYs) were calculated from 30 days after the date of first dialysis to the date of DNM diagnosis, kidney transplant, death, last follow-up or December 31, 2013, whichever came first. The risk of DNM, as compared to the general population, was estimated using standardized incidence ratios (SIRs) and 95% confidence intervals (CIs). RESULTS: During 10,798 PYs, 357 DNMs were diagnosed in 330 dialysis patients. A higher than expected risk of 1.3-fold was found for all DNMs combined (95% CI: 1.15-1.43). The risk was particularly high in younger dialysis patients (SIR = 1.88, 95% CI: 1.42-2.45 for age 40-59 years), and it decreased with age. Moreover, significantly increased DNM risks emerged during the first 3 years since dialysis initiation, especially within the first year (SIR = 8.52, 95% CI: 6.89-10.41). Elevated excess risks were observed for kidney (SIR = 3.18; 95% CI: 2.06-4.69), skin non-melanoma (SIR = 1.81, 95% CI: 1.46-2.22), oral cavity (SIR = 2.42, 95% CI: 1.36-4.00), and Kaposi's sarcoma (SIR = 10.29, 95% CI: 1.25-37.16). CONCLUSIONS: The elevated risk for DNM herein documented suggest the need to implement a targeted approach to cancer prevention and control in dialysis patients.openTaborelli, Martina; Toffolutti, Federica; Del Zotto, Stefania; Clagnan, Elena; Furian, Lucrezia; Piselli, Pierluca; Citterio, Franco; Zanier, Loris; Boscutti, Giuliano; Serraino, Diego for the Italian Transplant & Cancer Cohort Study; Sarah Shalaby, Raffaella Petrara, Patrizia Burra, Giacomo Zanus, Stefano Zanini,Paolo Rigotti; Maria Rendina, AlfredoDi Leo, Francesco Paolo Schena, Giuseppe Grandaliano, Marco Fiorentino, Augusto Lauro, Antonio Daniele Pinna, PaoloDi Gioia, Sara Pellegrini, Chiara Zanfi, Maria Piera Scolari, Sergio Stefoni, PaolaTodeschini, Laura Panicali, Chiara Valentini, Umberto Baccarani, Andrea Risaliti, Gian Luigi Adani, Dario Lorenzin, Giuseppe Maria Ettorre, Giovanni Vennarecci,Marco Colasanti, Manuela Coco, Fabrizio Ettorre, Roberto Santoro, LuciaMiglioresi, Francesco Nudo, Massimo Rossi,Gianluca Mennini, Luca Toti, GiuseppeTisone, Annachiara Casella, Laura Fazzolari, Daniele Sforza, Giuseppe Iaria,Carlo Gazia, Chiara Belardi, ClaudiaCimaglia, Alessandro Agresta, Gianpiero D’Offizi, Ubaldo Visco Comandini,Raffaella Lionetti, Marzia Montalbano, Chiara Taibi, Giovanni Fantola, Fausto Zamboni, Gian Benedetto Piredda,Maria Benigna Michittu, Maria Gavina Murgia, Bruno Onano, Lucia Fratino, Luigino Dal Maso, Paolo De Paoli, Diana Verdirosi,Emanuela Vaccher, Francesco Pisani, Antonio Famulari, Federica Delreno, Samuele Iesari, LindaDe Luca, Maurizio Iaria, Enzo Capocasale,Elena Cremaschi, Silvio Sandrini, Francesca Valerio,Valentina Mazzucotelli, Nicola Bossini, Gisella Setti, Massimiliano Veroux, Pierfrancesco Veroux, Giuseppe Giuffrida,Alessia Giaquinta, Domenico Zerbo, GhilBusnach, Laura Di Leo, Maria Luisa Perrino, Marialuisa Querques, ValerianaColombo, Maria Chiara Sghirlanzoni , Piergiorgio Messa, Antonio Leoni , Laura Galatioto, Salvatore Gruttadauria, Vito Sparacino, FlaviaCaputo, Barbara Buscemi ,Franco Cit-terio, Gionata Spagnoletti, Maria Paola Salerno, Evaldo Favi Giuseppe Paolo Segoloni, Luigi Biancone, AntonioLavacca, Maria Cristina Maresca, CarmeloCascone, Bice Virgilio, Donato Donati, Fiorella Dossi, Andrea Fontanella, Andrea Ambrosini, Marco Di CiccoTaborelli, Martina; Toffolutti, Federica; Del Zotto, Stefania; Clagnan, Elena; Furian, Lucrezia; Piselli, Pierluca; Citterio, Franco; Zanier, Loris; Boscutti, Giuliano; Serraino, Diego for the Italian Transplant & Cancer Cohort Study; Shalaby, Sarah; Petrara, MARIA RAFFAELLA; Burra, Patrizia; Zanus, Giacomo; Zanini, Stefano; Rigotti, Paolo; Maria, Rendina; Alfredodi, Leo; Francesco Paolo Schena, ; Giuseppe, Grandaliano; Marco, Fiorentino; Augusto, Lauro; Antonio Daniele Pinna, ; Paolodi, Gioia; Sara, Pellegrini; Chiara, Zanfi; Maria Piera Scolari, ; Sergio, Stefoni; Paolatodeschini, ; Laura, Panicali; Chiara, Valentini; Umberto, Baccarani; Andrea, Risaliti; Gian Luigi Adani, ; Dario, Lorenzin; Giuseppe Maria Ettorre, ; Giovanni, Vennarecci; Marco, Colasanti; Manuela, Coco; Fabrizio, Ettorre; Roberto, Santoro; Luciamiglioresi, ; Francesco, Nudo; Massimo, Rossi; Gianluca, Mennini; Luca, Toti; Giuseppetisone, ; Annachiara, Casella; Laura, Fazzolari; Daniele, Sforza; Giuseppe, Iaria; Carlo, Gazia; Chiara, Belardi; Claudiacimaglia, ; Alessandro, Agresta; Gianpiero, D’Offizi; Ubaldo Visco Comandini, ; Raffaella, Lionetti; Marzia, Montalbano; Chiara, Taibi; Giovanni, Fantola; Fausto, Zamboni; Gian Benedetto Piredda, ; Maria Benigna Michittu, ; Maria Gavina Murgia, ; Bruno, Onano; Lucia, Fratino; Luigino Dal Maso, ; Paolo De Paoli, ; Diana, Verdirosi; Emanuela, Vaccher; Francesco, Pisani; Antonio, Famulari; Federica, Delreno; Samuele, Iesari; Lindade, Luca; Maurizio, Iaria; Enzo, Capocasale; Elena, Cremaschi; Silvio, Sandrini; Francesca, Valerio; Valentina, Mazzucotelli; Nicola, Bossini; Gisella, Setti; Massimiliano, Veroux; Pierfrancesco, Veroux; Giuseppe, Giuffrida; Alessia, Giaquinta; Domenico, Zerbo; Ghilbusnach, ; Laura Di Leo, ; Maria Luisa Perrino, ; Marialuisa, Querques; Valerianacolombo, ; Maria Chiara Sghirlanzoni, ; Piergiorgio, Messa; Antonio, Leoni; Laura, Galatioto; Salvatore, Gruttadauria; Vito, Sparacino; Flaviacaputo, ; Barbara, Buscemi; Franco, Cit-terio; Gionata, Spagnoletti; Maria Paola Salerno, ; Evaldo Favi Giuseppe Paolo Segoloni, ; Luigi, Biancone; Antoniolavacca, ; Maria Cristina Maresca, ; Carmelocascone, ; Bice, Virgilio; Donato, Donati; Fiorella, Dossi; Andrea, Fontanella; Andrea, Ambrosini; Marco Di Cicco

Progress with the Upgrade of the SPS for the HL-LHC Era

The demanding beam performance requirements of the High Luminosity (HL-) LHC project translate into a set of requirements and upgrade paths for the LHC injector complex. In this paper the performance requirements for the SPS and the known limitations are reviewed in the light of the 2012 operational experience. The various SPS upgrades in progress and still under consideration are described, in addition to the machine studies and simulations performed in 2012. The expected machine performance reach is estimated on the basis of the present knowledge, and the remaining decisions that still need to be made concerning upgrade options are detailed.Comment: 3 p. Presented at 4th International Particle Accelerator Conference (IPAC 2013

Experimental Studies of Carbon Coatings as Possible Means of Suppressing Beam Induced Electron Multipacting in the CERN SPS

Electron cloud build-up is a major limitation for the operation of the SPS with LHC beam above nominal intensity. These beams are envisaged in the frame of the LHC luminosity upgrade and will be available from the new injectors LPSPL and PS2. A series of studies have been conducted in order to identify possible means to suppress electron multipacting by coating the existing SPS vacuum chambers with thin films of amorphous carbon. After a description of the experimental apparatus installed in the SPS, the results of the tests performed with beam in 2008 will be presented