Charged-Surface Instability Development in Liquid Helium; Exact Solutions

The nonlinear dynamics of charged-surface instability development was investigated for liquid helium far above the critical point. It is found that, if the surface charge completely screens the field above the surface, the equations of three-dimensional (3D) potential motion of a fluid are reduced to the well-known equations describing the 3D Laplacian growth process. The integrability of these equations in 2D geometry allows the analytic description of the free-surface evolution up to the formation of cuspidal singularities at the surface.Comment: latex, 5 pages, no figure

Phase Diagram of Multilayer Magnetic Structures

Multilayer "ferromagnet-layered antiferromagnet" (Fe/Cr) structures frustrated due to the roughness of layer interfaces are studied by numerical modeling methods. The "thickness-roughness" phase diagrams for the case of thin ferromagnetic film on the surface of bulk antiferromagnet and for two ferromagnetic layers separated by an antiferromagnetic interlayer are obtained and the order parameter distributions for all phases are found. The phase transitions nature in such systems is considered. The range of applicability for the "magnetic proximity model" proposed by Slonczewski is evaluated.Comment: 8 pages, 8 figure

Long-distance transfer of microwaves in sliding-mode virtual plasma waveguides

Experimentally an effective channeling and transfer of the sliding mode of the 35.3 GHz (λ ≈ 8.5 mm) microwave signal along 60 m distance has been demonstrated in the low-density (ne ∼ 1012 cm−3) 10 cm diameter hollow plasma waveguide created by the 100 ns UV pulse of GARPUN KrF laser in the laboratory air. The mechanism of the transfer is the total internal reflection of the signal on the optically less dense walls of the waveguide. The theory of this sliding mode propagation in large-diameter (D � λ) plasma waveguides is developed, which is in good accordance with our experimental results

Resistance of two-dimensional superconducting films

We consider the problem of finite resistance R in superconducting films with geometry of a strip of width W near zero temperature. The resistance is generated by vortex configurations of the phase field. In the first type of process, quantum phase slip, the vortex world line in 2+1 dimensional space-time is spacelike (i.e., the superconducting phase winds in time and space). In the second type, vortex tunneling, the world line is timelike (i.e., the phase winds in the two spatial directions) and connects opposite edges of the film. For moderately disordered samples, processes of the second type favor a train of vortices, each of which tunnels only across a fraction of the sample. Optimization with respect to the number of vortices yields a tunneling distance of the order of the coherence length ξ , and the train of vortices becomes equivalent to a quantum phase slip. Based on this theory, we find the resistance ln R ∼ − gW/ξ , where g is the dimensionless normal-state conductance. Incorporation of quantum fluctuations indicates a quantum phase transition to an insulating state for g 1

Charged particle acceleration by an intense wake-field excited in plasmas by either laser pulse or relativistic electron bunch

The results from theoretical and experimental studies, as well as from 2.5-dimensional (2.5-D) numerical simulation of plasma wake field excitation, by either relativistic electron bunch, laser pulse, and the charged particle wake field acceleration are discussed. The results of these investigations make it possible to evaluate the potentialities of the wake field acceleration method and to analyze whether it can serve as a basis for creating a new generation of devices capable of charged particle accelerating at substantially higher (on the order of two to three magnitudes) rates in comparison with those achievable in classical linear high-frequency (resonant) accelerators