The objective of the proposed project is to elucidate the nature of the flux line lattice (FLL) instabilities in type II superconductors. The main attention will be paid to the relation of the instabilities to the anisotropy of crystals, their shapes, and I-V characteristics. To attain this objective the following tasks will be solved.
1. The samples with controlled anisotropy and of desired shape will be prepared. They include single crystals and thin films of rare-earth-123, Bi-based, MgB2 superconductors, and specially formed mesoscopic structures. The anisotropy of the samples will be controlled by twin boundaries and heavy-ion irradiation, and regular mesoscopic arrays. As a result, the teams will have a comprehensive set of specially prepared and properly characterized samples to fulfil the research program;
2. The determination and analysis of the anisotropy parameters (components of the critical current density, I-V characteristics) using measurements of the ac magnetic susceptibility, static magnetization, four-probe and inductive transport methods, as well as the magneto-optical and Hall probe magnetic flux visualization will be performed. It is also planned to study the evolution of the FLL in the anisotropic samples under effect of crossed ac and dc magnetic fields. This study allows one to clarify the role of the anisotropy in non-stationary processes in high-Tc superconductors;
3. Flux flow instabilities will be directly observed using the advanced magneto-optical technique and the Hall probe method for the visualization of the flux structures. These techniques allow us to study the flux line lattice dynamics in a wide magnetic field range with the resolution up to individual vortices. The striking phenomenon of the flux turbulence in YBCO crystals will be studied accounting for the real I-V characteristics as well as the effect of the controlled sample anisotropy. A special attention will be focused on the dendritic instability of the flux penetration recently discovered in MgB2. The noise and dissipation phenomena accompanying the different kinds of instabilities will be analysed to reveal the characteristic features of the flux dynamics;
4. Using the advantages of the magneto-optical technique and earlier developed theoretical approaches, the local characteristics of the flux-line structure close to the mesoscopic objects (such as quantum dots and their arrays) will be determined.

It is expected to reveal the mechanism and give adequate theoretical description of the macroturbulence in anisotropic superconductors and to clarify the origin of the dendritic instability. Additionally, new approaches to the analysis of the electromagnetic processes in anisotropic superconductors will be elaborated. The possible types of the magnetic flux instabilities in superconductors with regular mesoscopic arrays of pinning sites will be found.
The main result of the project is filling, at least partially, a gap in the in the current knowledge in the electrodynamics of type II superconductors related to the problem of the FLL instabilities.