Results 1 - 10 of 5568
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[en] We report demonstrations of ion charge-state enhancement for an electron-beam metal-vapor vacuum-arc (E-MEVVA) ion source. Results with a lead cathode yielded a maximum ion charge state of Pb7+, which implies an ionization potential of at least 130 eV. Electron current densities j=70A/cm2 and ionization times τcongruent100μs produced jτ=9.2 x 10-3C/cm2 (5.8 x 1016electrons/cm2). Standard analysis for these conditions indicates -- somewhat surprisingly -- that successive single (stepwise) ionization accounts for the present observations, even though the charge states are substantially higher than most previous results with MEVVA-based ion sources. copyright 2001 American Institute of Physics
[en] High-nickel cathodes attract immense interest for use in lithium-ion batteries to boost Li-storage capacity while reducing cost. For overcoming the intergranular-cracking issue in polycrystals, single-crystals are considered an appealing alternative, but aggravating concerns on compromising the ionic transport and kinetic properties. We report here a quantitative assessment of redox reaction in single-crystal LiNiMnCoO using operando hard X-ray microscopy/spectroscopy, revealing a strong dependence of redox kinetics on the state of charge (SOC). Specifically, the redox is sluggish at low SOC but increases rapidly as SOC increases, both in bulk electrodes and individual particles. The observation is corroborated by transport measurements and finite-element simulation, indicating that the sluggish kinetics in single-crystals is governed by ionic transport at low SOC and may be alleviated through synergistic interaction with polycrystals integrated into a same electrode. (© 2020 Wiley‐VCH GmbH)
[en] We solve a two dimensional model describing the interaction of fermions with time dependent external fields. We work out the second quantized formulation and obtain conditions for equivalence of representations at different times. This implies the existence of sectors which describe charged states. We obtain the time dependence of charges and observe that charge differences become integer for unitary equivalent states. For scattering we require the equivalence of in- and out-representations; nevertheless charged sectors may be reached by suitable interactions and ionization is possible. 20 refs. (Author)
[en] In this paper, we report visible light emission from 320 keV Krq+ (4 ≤ q ≤ 9) ions on the Cu target. The wavelength range measured is from 300 nm to 656 nm. Two Cu I spectra deriving from different initial states and one Kr I line are detected. Specifically, the two Cu I lines belong to transitions 3d104p(2P03/2) − 3d104s (2S1/2) at 324.78 nm (A) and 3d104p(2P01/2) − 3d104s(2S1/2) at 327.42 nm (B), respectively, and the photon yield ratio of spectra lines (A) and (B) are about 2:1. The Kr I line belongs to transition 4s24p5(2P03/2)11d 2[3/2]0 − 4s24p5(2P03/2)5p 2[1/2] at 486.12 nm (C). In addition, the experimental results show that the photon yields of all lines are increasing with the charge state increase.
[en] The charge states of divacancies induced by 5 MeV self-implantation of doped silicon were investigated by positron annihilation methods. For low doping concentrations, results were found to be in agreement with the predictions of Fermi statistics. For the case of heavily boron-doped silicon (nB=1times1019cm-3) an anomalous single-negative divacancy charge state was detected. We attribute this to the introduction of new levels in the band gap, due to the capture of boron by divacancies, resulting in a boron-divacancy complex. Detailed analysis of positron annihilation spectra suggests that the boron does not reside on a nearest-neighbor site to the divacancy. Isothermal annealing experiments yield activation energy of 0.9±0.1eV for migration of this defect. [copyright] 2001 American Institute of Physics
[en] Based on the idea of a space-charge-limited mode of operation, the influence of a pair of electrostatic meshes on the beam parameters of the LBNL MEVVA-5 ion source was investigated. The meshes were placed in the expansion zone of the vacuum arc plasma. Apart from reducing the level of beam current fluctuations, this mode of operation provides significant control over the ion charge state distribution of the extracted beam. These effects can be understood taking not only space charge but also the high-directed ion drift velocities into account that are the same for different ion charge states of a material. The results of simulations of the processes involved are in good agreement with the experimental results
[en] The electric charge state and relaxation processes in HDPE+ZrO2 nanocomposites modified by the effect of γ rays have ben investigated by the thermostimulated depolarization method.Measurements have been carried out at a temperature range of 25 - 165 degreeC for pure high density polyethylene (HDPE), as well as polymer composite samples obtained with spherical nano-ZrO2 particles at different mass percentages (1 - 20%).Comparative analysis of TSD spectra of nanocomposite has been identified that the depolarization maxima occurring in the spectra take place on interphase boundaries both in the matrix, and in PE-ZrO2 nanocomposite samples as a result of the relaxation of stabilized charges in the corresponding temperature regions after corona polarization.It has been established that when the amount of filler n-ZrO2 nanoparticles is about 3 - 10%, the relaxation processes of electret charge is weakened.