Search results for "Surfaces and interfaces"
showing 10 items of 939 documents
Microstructure development during NiAl intermetallic synthesis in reactive Ni–Al nanolayers: Numerical investigations vs. TEM observations
2013
Abstract Heterogeneous reactions leading to the formation of intermetallic compounds in nanometric Ni–Al multilayer system are examined both numerically and experimentally. On the numerical side, the reactivity of a layered Ni–Al–Ni system is studied by means of molecular dynamics simulations, using an embedded-atom method (EAM) potential. The mechanism of nucleation and growth of the intermetallic phase is determined. Four main stages in the reactive process, which lead to the formation of rounded shape grains of intermetallic phase at the Ni–Al interface, are delineated. On the experimental side, TEM imaging of quenched samples revealed the behavior of the Ni–Al reactive foils and showed …
Label-free histamine detection with nanofluidic diodes through metal ion displacement mechanism
2017
[EN] We design and characterize a nanofluidic device for the label-free specific detection of histamine neurotransmitter based on a metal ion displacement mechanism. The sensor consists of an asymmetric polymer nanopore fabricated via ion track-etching technique. The nanopore sensor surface having metal-nitrilotriacetic (NTA-Ni2+) chelates is obtained by covalent coupling of native carboxylic acid groups with N-alpha,N-alpha-bis(carboxymethyl)-L-lysine (BCML), followed by exposure to Ni2+ ion solution. The BCML immobilization and subsequent Ni2+ ion complexation with NTA moieties change the surface charge concentration, which has a significant impact on the current-voltage (I-V) curve after…
Wormlike Polystyrene Brushes in Thin Films
1997
Mono- and multilayer films were prepared on mica by solution casting of a high molecular weight polymacromonomer, i.e., a polymethacrylate of about 1000 repeating units each of which was substituted by a polystyrene chain with a molecular weight of about 5000 Da. The films were studied by tapping scanning force microscopy. The material showed a remarkable preference for forming well-defined monolayers of a thickness of 6.5 ± 0.2 nm consistent with the hard core diameter of the collapsed cylindrical brush molecules. When the films were probed with high normal force, the single molecules were observed to organize in a dense nematic-like packing as expected for inherently stiff molecules. In o…
Effect of ion irradiation on the stability of amorphous Ge2Sb2Te5 thin films
2008
The archival life of phase-change memories (PCM) is determined by the thermal stability of amorphous phase in a crystalline matrix. In this paper, we report the effect of ion beam irradiation on the crystallization kinetics of amorphous Ge2Sb2Te5 alloy (GST). The transition rate of amorphous GST films was measured by in situ time resolved reflectivity (TRR). The amorphous to crystal transformation time decreases considerably in irradiated amorphous GST samples when ion fluence increases. The stability of amorphous Ge2Sb2Te5 thin films subjected to ion irradiation is discussed in terms of the free energy variation of the amorphous state because of damage accumulation. © 2008 Elsevier B.V. Al…
Effect of double frequency heating on the lead afterglow beam currents of an electron cyclotron resonance ion source
2017
International audience; The effect of double frequency heating on the performance of the CERN GTS-LHC 14.5 GHz ElectronCyclotron Resonance (ECR) ion source in afterglow mode is reported. The source of the secondary microwave frequency was operated both in pulsed and continuous wave (CW) modes within the range of 12–18 GHz. The results demonstrate that the addition of the secondary frequency can significantly impact the extracted beam currents and the temporal stability of the beam during the afterglow discharge. For example, up to a factor of 2.6 increase was achieved for 208Pb35+ and a factor of 3.1 for 208Pb37+ compared to single frequency afterglow currents. It is shown that these effect…
Vacuum electrical breakdown conditioning study in a parallel plate electrode pulsed dc system
2019
Conditioning of a metal structure in a high-voltage system is the progressive development of resistance to vacuum arcing over the operational life of the system. This is, for instance, seen during the initial operation of radio frequency (rf) cavities in particle accelerators. It is a relevant topic for any technology where breakdown limits performance and where conditioning continues for a significant duration of system run time. Projected future linear accelerators require structures with accelerating gradients of up to 100 MV/m. Currently, this performance level is achievable only after a multimonth conditioning period. In this work, a pulsed dc system applying voltage pulses over paral…
Diagnostics of a charge breeder electron cyclotron resonance ion source helium plasma with the injection ofNa231+ions
2016
This work describes the utilization of an injected 23Na1+ ion beam as a diagnostics of the helium plasma of a charge breeder electron cyclotron resonance ion source. The obtained data allows estimating the upper limit for the ion-ion collision mean-free path of the incident sodium ions, the lower limit of ion-ion collision frequencies for all charge states of the sodium ions and the lower limit of the helium plasma density. The ion-ion collision frequencies of high charge state ions are shown to be at least on the order of 1–10 MHz and the plasma density is estimated to be on the order of 1011 cm−3 or higher. The experimental results are compared to simulations of the 23Na1+ capture into t…
Toroidal magnetized iron neutrino detector for a neutrino factory
2013
A neutrino factory has unparalleled physics reach for the discovery and measurement of CP violation in the neutrino sector. A far detector for a neutrino factory must have good charge identification with excellent background rejection and a large mass. An elegant solution is to construct a magnetized iron neutrino detector (MIND) along the lines of MINOS, where iron plates provide a toroidal magnetic field and scintillator planes provide 3D space points. In this paper, the current status of a simulation of a toroidal MIND for a neutrino factory is discussed in light of the recent measurements of large theta(13). The response and performance using the 10 GeV neutrino factory configuration ar…
High-gradient testing of an $S$-band, normal-conducting low phase velocity accelerating structure
2020
A novel high-gradient accelerating structure with low phase velocity, $v/c=0.38$, has been designed, manufactured and high-power tested. The structure was designed and built using the methodology and technology developed for CLIC $100\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ high-gradient accelerating structures, which have speed of light phase velocity, but adapts them to a structure for nonrelativistic particles. The parameters of the structure were optimized for the compact proton therapy linac project, and specifically to 76 MeV energy protons, but the type of structure opens more generally the possibility of compact low phase velocity linacs. The structure operates in S-band, is backward…
High intensity neutrino oscillation facilities in Europe
2013
The EUROnu project has studied three possible options for future, high intensity neutrino oscillation facilities in Europe. The first is a Super Beam, in which the neutrinos come from the decay of pions created by bombarding targets with a 4 MW proton beam from the CERN High Power Superconducting Proton Linac. The far detector for this facility is the 500 kt MEMPHYS water Cherenkov, located in the Frejus tunnel. The second facility is the Neutrino Factory, in which the neutrinos come from the decay of mu(+) and mu(-) beams in a storage ring. The far detector in this case is a 100 kt magnetized iron neutrino detector at a baseline of 2000 km. The third option is a Beta Beam, in which the neu…