7,614 research outputs found
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
- …