arXiv subjects
Publications and source records attributed to S. V. Vasiliev.
We consider second order linear differential operators possessing a term depending on the unknown function with a fixed argument and study the uniqueness of recovering the operators from the spectrum. We also obtain a constructive procedure for solving this inverse problem along with necessary and sufficient conditions of its solvability.
We studied the critical state stability in a large cubic sample of a single crystalline La(1.85)Sr(0.15)CuO(4) for different sample orientations with respect to the external magnetic field as well as the dynamics of the flux jumps. It is shown that thermomagnetic avalanches develop in dynamic conditions characterized by significantly lower magnetic diffusivity than the thermal one. In this case, critical state stability depends strongly on cooling conditions. We compared predictions of the isothermal model and of the model for the weakly cooled sample with experimental results. In both models, the field of the first flux jump decreases with an increase of sweep rate of the external magnetic field. We also investigated the influence of external magnetic field on the dynamics of the following stages of the thermomagnetic avalanche. It is shown that the dynamics of the flux jumps is correlated with the magnetic diffusivity proportional to the flux flow resistivity.
We have monitored new peculiarities of the dynamics of catastrophic avalanches of the magnetic flux in superconducting Nb, Nb-Ti, and YBaCuO samples: i) convergent oscillations of the magnetic flux; ii) a threshold for entering the huge flux avalanches in the shielding experiments; iii) a threshold for the exit of a residual flux in the trapping experiments. The observed phenomena are interpreted in terms of a theoretical model which takes into account the inertial properties of the vortex matter.