The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Tao Qian - One of the best experts on this subject based on the ideXlab platform.
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selenium doped carbon nanosheets with strong Electron Cloud delocalization for nondeposition of metal oxides on air cathode of zinc air battery
ACS Applied Materials & Interfaces, 2019Co-Authors: Mengfan Wang, Tao QianAbstract:The deposition of metal oxides on the air cathode is a well-known problem for metal–air batteries, since it can cover the active surface and block the oxygen gas diffusion pathway, resulting in poor battery performance and serious cell degeneration. Herein, through deliberate selenium doping in nitrogen-doped carbon, a strong Electron Cloud delocalization among the carbon matrix is realized, which can prevent the air cathode from zinc oxide poisoning during zinc–air battery operation, as confirmed by experimental results and density functional theory simulations. In situ X-ray powder diffraction observation confirms that the increased Electron Cloud density of the surrounding carbon caused by Electron delocalization from selenium atom could repulse the access of zincate ions, effectively prohibiting the oxide deposition on the air cathode. An amazingly long zinc–air battery cycle life reaching 780 cycles is thus obtained.
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Selenium-Doped Carbon Nanosheets with Strong Electron Cloud Delocalization for Nondeposition of Metal Oxides on Air Cathode of Zinc–Air Battery
2019Co-Authors: Sisi Liu, Mengfan Wang, Tao Qian, Jie Liu, Chenglin YanAbstract:The deposition of metal oxides on the air cathode is a well-known problem for metal–air batteries, since it can cover the active surface and block the oxygen gas diffusion pathway, resulting in poor battery performance and serious cell degeneration. Herein, through deliberate selenium doping in nitrogen-doped carbon, a strong Electron Cloud delocalization among the carbon matrix is realized, which can prevent the air cathode from zinc oxide poisoning during zinc–air battery operation, as confirmed by experimental results and density functional theory simulations. In situ X-ray powder diffraction observation confirms that the increased Electron Cloud density of the surrounding carbon caused by Electron delocalization from selenium atom could repulse the access of zincate ions, effectively prohibiting the oxide deposition on the air cathode. An amazingly long zinc–air battery cycle life reaching 780 cycles is thus obtained
G Rumolo - One of the best experts on this subject based on the ideXlab platform.
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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
Physical review accelerators and beams, 2018Co-Authors: Eleonora Belli, G Rumolo, Costa P Pinto, M Taborelli, A. Sapountzis, T. Sinkovits, M. Zobov, G. Castorina, B Spataro, M. MiglioratiAbstract: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.
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Electron Cloud buildup driving spontaneous vertical instabilities of stored beams in the large hadron collider
Physical review accelerators and beams, 2018Co-Authors: Annalisa Romano, Giovanni Iadarola, Oliver Boinefrankenheim, Xavier Buffat, G RumoloAbstract:A beam instability driven by an Electron Cloud manifests itself hours after beam injection, when the beam intensity has significantly decreased from its maximum initial value.
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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
American Physical Society, 2018Co-Authors: E. Elli, G Rumolo, Costa P Pinto, M Taborelli, A. Sapountzis, T. Sinkovits, . Spataro, M. Zobov, G. Castorina, M. MiglioratiAbstract: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
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proceedings of eCloud 12 joint infn cern eucard accnet workshop on Electron Cloud effects la biodola isola d elba italy 5 9 jun 2012
arXiv: Accelerator Physics, 2014Co-Authors: R Cimino, G Rumolo, F ZimmermannAbstract:This report contains the Proceedings of the Joint INFN-Frascati, INFN-Pisa, CERN-LER and EuCARD-AccNet Mini-Workshop on Electron-Cloud Effects, "ECloud12", held at La Biodola, Isola d'Elba, from 5 to 9 June 2012. The ECloud12 workshop reviewed many recent Electron-Cloud (EC) observations at existing storage rings, EC predictions for future accelerators, Electron-Cloud studies at DAFNE, EC mitigation by clearing electrodes and graphite/carbon coatings, modeling of incoherent EC effects, self-consistent simulations, synergies with other communities like the Valencia Space Consortium and the European Space Agency. ECloud12 discussed new EC observations at existing machines including LHC, CesrTA, PETRA-3, J-PARC, and FNAL MI; latest experimental efforts to characterize the EC - including EC diagnostics, experimental techniques, mitigation techniques such as coating and conditioning, advanced chemical and physical analyses of various vacuum-chamber surfaces, beam instabilities and emittance growth -; the status of EC physics models and (new, more versatile and additional) simulation codes and their comparison with recently acquired experimental data; and the mitigation requirements and potential performance limitations imposed by the EC on upgraded and future machines, including HL-LHC, FAIR, ILC, Project-X, SuperB and SuperKEKB. A dedicated session addressed problems related to RF breakdown and multipacting for space applications. A number of open questions and future R&D needs were identified.
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benchmarking headtail with Electron Cloud instabilities observed in the lhc
arXiv: Accelerator Physics, 2013Co-Authors: Hannes Bartosik, W Hofle, Giovanni Iadarola, Y Papaphilippou, G RumoloAbstract:After a successful scrubbing run in the beginning of 2011, the LHC can be presently operated with high intensity proton beams with 50 ns bunch spacing. However, strong Electron Cloud effects were observed during machine studies with the nominal beam with 25 ns bunch spacing. In particular, fast transverse instabilities were observed when attempting to inject trains of 48 bunches into the LHC for the first time. An analysis of the turn-by-turn bunch-bybunch data from the transverse damper pick-ups during these injection studies is presented, showing a clear signature of the Electron Cloud effect. These experimental observations are reproduced using numerical simulations: the Electron distribution before each bunch passage is generated with PyECloud and used as input for a set of HEADTAIL simulations. This paper describes the simulation method as well as the sensitivity of the results to the initial conditions for the Electron build-up. The potential of this type of simulations and their clear limitations on the other hand are discussed.
Mengfan Wang - One of the best experts on this subject based on the ideXlab platform.
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selenium doped carbon nanosheets with strong Electron Cloud delocalization for nondeposition of metal oxides on air cathode of zinc air battery
ACS Applied Materials & Interfaces, 2019Co-Authors: Mengfan Wang, Tao QianAbstract:The deposition of metal oxides on the air cathode is a well-known problem for metal–air batteries, since it can cover the active surface and block the oxygen gas diffusion pathway, resulting in poor battery performance and serious cell degeneration. Herein, through deliberate selenium doping in nitrogen-doped carbon, a strong Electron Cloud delocalization among the carbon matrix is realized, which can prevent the air cathode from zinc oxide poisoning during zinc–air battery operation, as confirmed by experimental results and density functional theory simulations. In situ X-ray powder diffraction observation confirms that the increased Electron Cloud density of the surrounding carbon caused by Electron delocalization from selenium atom could repulse the access of zincate ions, effectively prohibiting the oxide deposition on the air cathode. An amazingly long zinc–air battery cycle life reaching 780 cycles is thus obtained.
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Selenium-Doped Carbon Nanosheets with Strong Electron Cloud Delocalization for Nondeposition of Metal Oxides on Air Cathode of Zinc–Air Battery
2019Co-Authors: Sisi Liu, Mengfan Wang, Tao Qian, Jie Liu, Chenglin YanAbstract:The deposition of metal oxides on the air cathode is a well-known problem for metal–air batteries, since it can cover the active surface and block the oxygen gas diffusion pathway, resulting in poor battery performance and serious cell degeneration. Herein, through deliberate selenium doping in nitrogen-doped carbon, a strong Electron Cloud delocalization among the carbon matrix is realized, which can prevent the air cathode from zinc oxide poisoning during zinc–air battery operation, as confirmed by experimental results and density functional theory simulations. In situ X-ray powder diffraction observation confirms that the increased Electron Cloud density of the surrounding carbon caused by Electron delocalization from selenium atom could repulse the access of zincate ions, effectively prohibiting the oxide deposition on the air cathode. An amazingly long zinc–air battery cycle life reaching 780 cycles is thus obtained
J P Sikora - One of the best experts on this subject based on the ideXlab platform.
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Electron Cloud density measurements in accelerator beam pipe using resonant microwave excitation
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2014Co-Authors: J P Sikora, B Carlson, Danielle Duggins, K C Hammond, Stefano De Santis, Alister J TencateAbstract:Abstract An accelerator beam can generate low energy Electrons in the beam-pipe, generally called Electron Cloud, that can produce instabilities in a positively charged beam. One method of measuring the Electron Cloud density is by coupling microwaves into and out of the beam-pipe and observing the response of the microwaves to the presence of the Electron Cloud. In the original technique, microwaves are transmitted through a section of beam-pipe and a change in EC density produces a change in the phase of the transmitted signal. This paper describes a variation on this technique in which the beam-pipe is resonantly excited with microwaves and the Electron Cloud density calculated from the change that it produces in the resonant frequency of the beam-pipe. The resonant technique has the advantage that measurements can be localized to sections of beam-pipe that are a meter or less in length with a greatly improved signal to noise ratio.
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shielded button electrodes for time resolved measurements of Electron Cloud buildup
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2014Co-Authors: J Crittenden, M Palmer, Michael Billing, J P SikoraAbstract:Abstract We report on the design, deployment and signal analysis for shielded button electrodes sensitive to Electron Cloud buildup at the Cornell Electron Storage Ring. These simple detectors, derived from a beam-position monitor electrode design, have provided detailed information on the physical processes underlying the local production and the lifetime of Electron densities in the storage ring. Digitizing oscilloscopes are used to record Electron fluxes incident on the vacuum chamber wall in 1024 time steps of 100 ps or more. The fine time steps provide a detailed characterization of the Cloud, allowing the independent estimation of processes contributing on differing time scales and providing sensitivity to the characteristic kinetic energies of the Electrons making up the Cloud. By varying the spacing and population of Electron and positron beam bunches, we map the time development of the various Cloud production and re-absorption processes. The excellent reproducibility of the measurements also permits the measurement of long-term conditioning of vacuum chamber surfaces.
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Electron Cloud buildup characterization using shielded pickup measurements and custom modeling code at cesrta
arXiv: Accelerator Physics, 2013Co-Authors: J Crittenden, J P SikoraAbstract:The Cornell Electron Storage Ring Test Accelerator experimental program includes investigations into Electron Cloud buildup, applying various mitigation techniques in custom vacuum chambers. Among these are two 1.1-m-long sections located symmetrically in the east and west arc regions. These chambers are equipped with pickup detectors shielded against the direct beam-induced signal. They detect Cloud Electrons migrating through an 18-mm-diameter pattern of small holes in the top of the chamber. A digitizing oscilloscope is used to record the signals, providing time-resolved information on Cloud development. Carbon-coated, TiN-coated and uncoated aluminum chambers have been tested. Electron and positron beams of 2.1, 4.0 and 5.3 GeV with a variety of bunch populations and spacings in steps of 4 and 14 ns have been used. Here we report on results from the ECloud modeling code which highlight the sensitivity of these measurements to the physical phenomena determining Cloud buildup such as the photoElectron production azimuthal and energy distributions, and the secondary yield parameters including the true secondary, re-diffused, and elastic yield values.
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resonant te wave measurement of Electron Cloud density using multiple sidebands
2013Co-Authors: J P Sikora, S De Santis, Calculating SpectraAbstract:A change in Electron Cloud (EC) density will change the resonant frequency of a section of beam-pipe. With a fixed drive frequency, the resulting dynamic phase shift across the resonant section will include the convolution of the frequency shift with the impulse response of the reso- nance. The effect of the convolution on the calculated mod- ulation sidebands is in agreement with measured data, in- cluding the absolute value of the EC density obtained from ECloud simulations. These measurements were made at the Cornell Electron Storage Ring (CESR) which has been reconfigured as a test accelerator (CESRTA) with positron or Electron beam energies ranging from 2 GeV to 5 GeV.
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modeling for time resolved retarding field analyzer measurements of Electron Cloud buildup at cesrta
2013Co-Authors: J Crittenden, Xianghong Liu, M A Palmer, J P SikoraAbstract:The Cornell Electron Storage Ring Test Accelerator program includes investigations into Electron Cloud buildup mitigation techniques using custom vacuum chambers. Multibunch Electron and positron beams of energies between 2.1 and 5.3 GeV with bunch spacings from 4 to 98 ns and bunch populations ranging from 1e10 to 16e10 provide highly differentiated sensitivity to the processes contributing to Cloud buildup such as photoElectron production, Cloud space-charge dynamics, and secondary Electron emission. Measurements of the time dependence of Cloud buildup using BPM-style shielded pickups have been shown to provide tight constraints on Cloud buildup models. Recently, time-resolving retarding-field analyzers have been designed, installed and commissioned. These novel detectors combine the time-resolving feature of the shielded pickups with the fine transverse segmentation and Cloud Electron energy sensitivity of the time-integrating retarding-field analyzers used previously. We report on progress in modeling these measurements and quantify their sensitivity to various parameters describing the underlying physical processes contributing to Cloud buildup.
F Zimmermann - One of the best experts on this subject based on the ideXlab platform.
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proceedings of eCloud 12 joint infn cern eucard accnet workshop on Electron Cloud effects la biodola isola d elba italy 5 9 jun 2012
arXiv: Accelerator Physics, 2014Co-Authors: R Cimino, G Rumolo, F ZimmermannAbstract:This report contains the Proceedings of the Joint INFN-Frascati, INFN-Pisa, CERN-LER and EuCARD-AccNet Mini-Workshop on Electron-Cloud Effects, "ECloud12", held at La Biodola, Isola d'Elba, from 5 to 9 June 2012. The ECloud12 workshop reviewed many recent Electron-Cloud (EC) observations at existing storage rings, EC predictions for future accelerators, Electron-Cloud studies at DAFNE, EC mitigation by clearing electrodes and graphite/carbon coatings, modeling of incoherent EC effects, self-consistent simulations, synergies with other communities like the Valencia Space Consortium and the European Space Agency. ECloud12 discussed new EC observations at existing machines including LHC, CesrTA, PETRA-3, J-PARC, and FNAL MI; latest experimental efforts to characterize the EC - including EC diagnostics, experimental techniques, mitigation techniques such as coating and conditioning, advanced chemical and physical analyses of various vacuum-chamber surfaces, beam instabilities and emittance growth -; the status of EC physics models and (new, more versatile and additional) simulation codes and their comparison with recently acquired experimental data; and the mitigation requirements and potential performance limitations imposed by the EC on upgraded and future machines, including HL-LHC, FAIR, ILC, Project-X, SuperB and SuperKEKB. A dedicated session addressed problems related to RF breakdown and multipacting for space applications. A number of open questions and future R&D needs were identified.
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Electron Cloud effects in past and future machines walk through 50 years of Electron Cloud studies
arXiv: Accelerator Physics, 2013Co-Authors: F ZimmermannAbstract:Past Electron-Cloud (e-Cloud) observations, studies and mitigation techniques are quickly reviewed along with some ongoing code developments, the preceding ECloud workshops, recent contacts with the spacecraft community, the important role of Francesco Ruggiero, and a few current Electron-Cloud topics discussed at ECloud12 in La Biodola.
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first Electron Cloud studies at the large hadron collider
Physical Review Special Topics-accelerators and Beams, 2013Co-Authors: O Dominguez, F Zimmermann, G Rumolo, G Arduini, E Metral, Maury H CunaAbstract:During the beam commissioning of the Large Hadron Collider (LHC) [LHC Design Report No. CERN-2004-003-V-1, 2004 [http://cds.cern.ch/record/782076?ln=en]; O. Bruning, H. Burkhardt, and S. Myers, Prog. Part. Nucl. Phys. 67, 705 (2012)] with 150, 75, 50, and 25-ns bunch spacing, important Electron-Cloud effects, like pressure rise, cryogenic heat load, beam instabilities, or emittance growth, were observed. Methods have been developed to infer different key beam-pipe surface parameters by benchmarking simulations and pressure rise as well as heat-load observations. These methods allow us to monitor the scrubbing process, i.e., the reduction of the secondary emission yield as a function of time, in order to decide on the most appropriate strategies for machine operation. To better understand the influence of Electron Clouds on the beam dynamics, simulations have been carried out to examine both the coherent and the incoherent effects on the beam. In this paper we present the methodology and first results for the scrubbing monitoring process at the LHC. We also review simulated instability thresholds and tune footprints for beams of different emittance, interacting with an Electron Cloud in field-free or dipole regions.
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simulation of Electron Cloud heat load for the cold arcs of the large hadron collider
Conf. Proc., 2012Co-Authors: Humberto Maury Cuna, F Zimmermann, Giovanni Iadarola, G RumoloAbstract:The heat load due to the Electron Cloud in the Large Hadron Collider (LHC) cold arcs is a concern for its performance near and beyond nominal beam current. We report the results of simulation studies, which examine the Electron-Cloud induced heat load for different values of low-energy Electron reflectivity and secondary emission yield at injection energy, as well as at beam energies of 4 TeV and 7 TeV, for two different bunch spacing: 25 ns and 50 ns. Benchmarking the simulations against heatload observations at different beam energies and bunch spacings allows an estimate of the secondary emission yield in the cold arcs of the LHC and of its evolution as a function of time.
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simulations of Electron Cloud heat load for the cold arcs of the cern large hadron collider and its high luminosity upgrade scenarios
Physical Review Special Topics-accelerators and Beams, 2012Co-Authors: Humberto Maury Cuna, Jesus Guillermo Contreras, F ZimmermannAbstract:The heat load generated by an Electron Cloud in the cold arcs of the Large Hadron Collider (LHC) is a concern for operation near and beyond nominal beam current. We report the results of simulation studies, with updated secondary-emission models, which examine the severity of the Electron heat load over a range of possible operation parameters, both for the nominal LHC and for various luminosity-upgrade scenarios, such as the so-called ``full crab crossing'' and ``early separation'' schemes, the ``large Piwinski angle'' scheme, and a variant of the latter providing ``compatibility'' with the (upgraded) LHCb experiment. The variable parameters considered are the maximum secondary-emission yield, the number of particles per bunch, and the spacing between bunches. In addition, the dependence of the heat load on the longitudinal bunch profile is investigated.