"Technical Physics Letters"

Mikheeva, G. M.;Mogileva, T. N.;Okotrub, A. V.;Vanyukov, V. V.

doi: 10.1134/S1063785010030016pmid: N/A

Abstract An improved scheme of z-scanning was used to study the parameters of nanosecond 1064-nm laser radiation pulses scattered at right angle under the conditions of optical limiting in an aqueous suspension of purified carbon nanotubes (CNTs). CNTs were synthesized by the electric-arc evaporation of graphite. It is established that the amplitude, shape, duration, and temporal position of the peak of scattered light pulses significantly depend on the laser radiation power density. The results agree with the mechanism of thermoinduced nonlinear scattering that is operative during the optical limiting of laser pulses in CNT suspensions.

Zarikovskaya, N. V.;Zuev, L. B.

doi: 10.1134/S1063785010030028pmid: N/A

Abstract Characteristics of the plastic strain macrolocalization are compared to parameters of the Hall-Petch relation for the flow stress in polycrystalline aluminum samples with grain sizes ranging from 0.008 to 5 mm. It is established that, in the range of brain sizes studied, there are two possible types of the dependence of the length of localized strain autowave on the grain size and two variants of the Hall-Petch relation. It is shown that the boundary between the two variants in both cases corresponds to d ≈ 0.1 mm. Interconnection of the patterns of plastic flow localization and the Hall-Petch relation is traced.

Pozdnyakov, A. O.;Ginzburg, B. M.;Pozdnyakov, O. F.

doi: 10.1134/S106378501003003Xpmid: N/A

Abstract The molecular compositions of products formed during the friction of polymers [poly(methyl methacrylate), polystyrene] in both symmetric (same materials) and asymmetric (different materials) polymer-on-polymer friction pairs have been determined by using mass spectrometry. In addition to monomers, which are formed during friction as a result of the depolymerization of the corresponding free macroradicals, the mass spectra reveal new products. The formation of these products is explained by the interaction of monomers with hydrogen molecules, which are also formed in the contact zone.

Altmark, A. M.;Kanareykin, A. D.

doi: 10.1134/S1063785010030041pmid: N/A

Abstract The wakefield electron acceleration scheme provides effective means of creating high accelerating field gradients in both dielectric-lined waveguide structures and plasma. We have studied the influence of errors in the structure of this scheme on the efficiency of energy transfer from the driving to witness (driven) electron bunches. Deviation of the wakefield frequency from the calculated optimum value leads to a misfit in the mutual positioning of bunches in the driving train and the corresponding decrease in the energy transformer ratio. It is suggested to compensate for the arising misfit by correcting distances between bunches in the driving train, with a resulting increase in the efficiency of energy transfer. Results of calculations are presented for a dielectric-filled 13-GHz structure with parameters of the Argonne Wakefield Accelerator.

Kaminsky, A. K.;Perel’shteĭn, É. A.;Sedykh, S. N.;Ginzburg, N. S.;Kuzikov, S. V.;Peskov, N. Yu.;Sergeev, A. S.

doi: 10.1134/S1063785010030053pmid: N/A

Abstract An effective narrow-band free-electron maser (FEM) with reversed axial guide magnetic field, based on a corrugated high-selectivity Bragg resonator with a jump in the ripple phase, has been constructed and tested. The FEM operates at 30 GHz with characteristics of the output radiation (power, pulse duration, spectrum width) and stability of the generation regime that allow the device to be used in testing electrodynamic components for future electron-positron supercolliders. Experiments have been performed with a high-Q resonator operating on a resonant load, which can be used to model the degradation of an accelerating structure of the CLIC collider (CERN) as a result of thermal fatigue caused by the multiply repeated (∼105 cycles) action of microwave pulses.

Korenbaum, V. I.;Tagil’tsev, A. A.

doi: 10.1134/S1063785010030065pmid: N/A

Abstract Experiments on a laboratory prototype setup showed that ultrasonic shear oscillations produce a statistically reliable decrease in the static yield point (normalized to the initial temperature) of crude oil in a near-wall layer at temperatures in the interval of −(13–17.5)°C. The observed effect amounted to about 19% at a specific power of ultrasonic oscillations on a level of 0.002 W/cm2.

Dubrovskii, V. G.

doi: 10.1134/S1063785010030077pmid: N/A

Abstract A theory of condensation is proposed for an open system in which the growth rate varies with the number of particles and the total particle concentration (supersaturation flux) varies with the time as described by power laws with arbitrary exponents (indices). It is established that the distribution of nuclei with respect to their sizes z, which is formed at the nucleation stage, is subject to fluctuational blurring. The dependence of the distribution width on the average size z is related in a nontrivial manner to the values of the growth and flux indices. Conditions for the onset of the Ostwald ripening (OR) stage in the system are analyzed with allowance for fluctuations in the number of particles. It is shown that the Kukushkin-Osipov criterion remains valid, since the transition curve occurs in a region where the distribution width grows slower than z. At the same time, the form of the initial condition and the character of evolution of the distribution at the OR stage significantly vary under the action of fluctuations.

Kondrashov, A. V.;Ustinov, A. B.;Kalinikos, B. A.

doi: 10.1134/S1063785010030089pmid: N/A

Abstract Controlled chaotic microwave generation under the conditions of four-wave parametric interaction of the surface spin waves has been experimentally studied in active resonance rings based on tangentially magnetized ferromagnetic films. It is shown that the chaotic microwave signal parameters can be effectively controlled.

Ladutenko, K. S.;Ankudinov, A. V.;Evtikhiev, V. P.

doi: 10.1134/S1063785010030090pmid: N/A

Abstract The region of the main potential drop in a sharp p +−n + junction in GaAs has been studied using the conventional and gradient scanning Kelvin probe force microscopy (KPFM) techniques. It is shown that the gradient method offers advantages for quantitative measurements. An algorithm for the program implementing the gradient KPFM method on standard commercial atomic-force microscopes is proposed. It is established that the layer of adsorbed water contributes to the measured width of the main potential drop region.

Londer, Ya. I.;Ul’yanov, K. N.

doi: 10.1134/S1063785010030107pmid: N/A

Abstract A two-dimensional mathematical model of a short high-current vacuum-arc discharge is developed, according to which magnetized electrons move in a hydrodynamic regime and fast cathode ions propagate in a free flight regime in a two-dimensional electric field. The proposed model takes into account the distribution of ions with respect to their escape angles from the cathode plasma boundary. A method for calculation of the plasma density distribution in the interelectrode gap is proposed. Two-dimensional distributions of the plasma density, electric field, and discharge current density in an external magnetic field are calculated. It is shown that ion trajectories exhibit mutual intersections, partly return to the cathode, and partly rotate in the oppositely oriented electric field at the side boundary of plasma. A decrease in the applied magnetic field intensity leads to a decrease in the number of ion trajectories reaching the anode (ion starvation), which can result in the violation of a stationary current transfer.