Repetitive high current density pseudospark-produced ion beams

Abstract

A multigap pseudospark device filled with hydrogen or argon gas is operated up to 20 kV and ejected ion beam characteristics are experimentally investigated. The ion beam of peak current density in excess of ∼500 A/cm2 and pulse duration ∼50 ns is extracted at repetitive frequency of several tens of Hz. Results of the scaling study for the ion beam current with breakdown voltage, external capacitance, and number of insulator gaps are presented.

Micro-Raman and Resistance Measurements of Epitaxial La0.7Sr0.3MnO3 Films

“…At low temperatures the tunneling is dumped leading to the observed resistance increasing. We can conclude that not only the oxygen annealing but even the use of oxygen as a working gas is not necessary for the deposition of high quality stoichiometrical films of La 0X7 Sr 0X3 MnO 3 . This means that the target molecules are not destroyed by Channel-Spark ablation, but move as separate molecules and small clusters of a stoichiometrical compound.…”

“…In order to estimate the film quality we shall mainly analyze the phonon peaks. Differently from the orthorhombic LaMnO 3 system [7], the phonon peaks of rhombohedrically distorted perovskite La 1Àx M x MnO 3 are not yet well identified. Nevertheless, by analogy the 200 and 425 cm À1 modes should reflect the rare-earth/MnO 6 vibration mode and the apical oxygen bending mode of MnO 6 octahedra, respectively.…”

“…Because of the radial component of the electrical field in the hollow cathode, the electron avalanches are focused to the vertical axis and escape as a tiny beam to the high voltage (up to 20 kV) acceleration section. In spite of the carrier repulsion, the magnetic self-pinching provides high current densities [3]. The resulting pulses have energy density of about 1 J cm À2 and duration about 100 ns.…”

“…Such outgrowths are typical for the perovskite films, and were in detail studied on 123 system thin films [7]. The spectra for both films consist of a sum of NdGaO 3 and La 0X7 Sr 0X3 MnO 3 spectra (the 425 cm À1 energy is indicated by dotted line). The La 0X7 Sr 0X3 MnO 3 mode is well visible, although it is slightly obscured by the substrate 405 cm À1 mode for the film 2.…”

“…Gas pressure was kept constant during the process ± ± P 3 Â 10 À2 mbar. The sample was heated by a stainless steel heater to temperatures about 700 to 750 C. Stoichiometrical targets were produced by a conventional pellet sintering [4] at 1200 or 1500 C, providing densities of about 5.5 and 6 g/cm 3 , respectively. Target±sample distance was about 40 mm.…”