Ultrasonic crystallizer of CuSO4 solution: Engineering simulation

Ultrasound crystallizer of copper sulfate solution based on creating the solidification front with the aid of a gradient of temperature, which was exposed to ultrasonic waves with use of a magnetostrictive transducer, was proposed. The algorithm for the calculation of critical process parameters of the crystallization was developed jointly using the differential transport equations of momentum, mass, energy, sound waves, and a method of similarity and dimensional analysis.     

Particle-in-cell simulation of generation of an HF sequence of short current pulses in the vircator with counter-propagating beams

We performed a particle-in-cell (PIC) simulation of a vircator with counter electron beams in a cylindrical cavity with metal walls. Two pairs of counter-propagating superlimiting electron beams with different energy and current in each pair are injected along the cylinder axis. It is found that the electron charge in the cavity is formed as a sequence of pulses corresponding to slow accumulation and fast discharge. It is shown that the pulses are related to the characteristic dynamics of the squeezed beam state, the distributed virtual cathode. This regime can be used to generate anHF sequence of ultrawideband electromagnetic pulses.     

Magnetochemical effects occurring upon treatment of the thin ferromagnetic film surface in an acidic medium

The results from magnetooptical studies of the influence of magnetochemical effects on the surface morphology and local magnetic properties of FeN alloy thin films and thin-film systems that consist of alternating silicon dioxide and FeN layers of submicron thickness, are shown. The dramatic influence of chemical etching on the surface morphology and magnetic characteristics of the investigated samples is revealed.     

Self-polarization and migratory polarization in thin lead zirconate-titanate films

This paper reports on a study of the electrical properties of 0.7–1-μm-thick textured PZT ferroelectric films prepared by rf magnetron sputtering of a PbZr_0.54Ti_0.46O₃ target which additionally contained 10 mol % lead oxide. Such films are shown to feature a combination of a self-polarized state and migratory polarization. The totality of the data obtained suggest that the films had n-type conduction. As shown by the laser beam modulation technique, the polarization was distributed nonuniformly in depth, with most of the poled state localized near the lower interface of the thin-film ferroelectric capacitor. The mechanism underlying the onset of this self-polarization is related to the charging of the lower interface of the structure by electrons, which occurs during the cooling following the high-temperature treatment of the PZT film, and to poling of the bulk of the film by the charged interface. This mechanism of the self-polarization of ferroelectric films is believed to have a universal character. __________ Translated from Fizika Tverdogo Tela, Vol. 44, No. 4, 2002, pp. 739–744. Original Russian Text Copyright ? 2002 by Pronin, Kaptelov, Tarakanov, Shaplygina, Afanas’ev, Pankrashkin.     

Simulation results of the Coulomb explosion of metal

By the example of a plasma layer, the problem of the Coulomb explosion of metal during exposure to a powerful picosecond laser pulse was numerically simulated. It was shown that plasma electrons leave the plasma layer under the ponderomotive force in the direction against the gradient of the laser radiation field, while ions fly apart in the field of the self-charge.     

The measurement and verification of parameters of pulse electromagnetic radiation generated by a large-radius ring current

Experimental and analytic studies of the generation and propagation of electromagnetic radiation due to repetitive current pulses of a nanosecond duration (peak power to 1 MW, current slew rate of 3.5 A/ns) are presented. The radiation source was a fine-wire ring antenna of large radius (ρ_a=1.4 m). The antenna was driven along its full length instantaneously within the time τ shorter than the time of wave travel along the ring diameter (τ≤2ρ_a/c). Parameters of the emitted wave were measured. The experimental data are consistent with the calculated emitted-wave parameters that take into account radiation reflection from the conducting walls of the laboratory. The efficiency of transformation of drive pulse energy into ultra-wideband radiation was found to be approximately 15%. A ring antenna driven by repetitive current pulses (within the time τ≤2ρ_a/c) is suggested to be used as a reference ultra-wideband emitter.