E. P. Krasnoperov

Developing an approach based on the formation of YBa2Cu3Ox-interlayer-YBa2Cu3Ox epitaxial structures with high current-carrying ability

An approach based on the formation of YBa2Cu3Ox-interlayer-YBa2Cu3Ox multilayer epitaxial structures with high current-carrying ability is proposed. The use of interlayers representing simple cubic oxides (SrTiO3 and CeO2) allows the growth of crystal defects during the formation of a high-temperature superconductor (HTS) layer to be stopped. The phenomenon of current transfer through 10- to 50-nm-thick interlayers has been discovered. Using the proposed approach, it is possible to increase the current-carrying ability in proportion to the number of HTS layers in the structure. This in principle solves the problem of critical current-density degradation with increasing thickness of YBa2Cu3Ox layer.

Magnetic flux relaxation in a pulse-magnetized Y-Ba-Cu-O superconductor

Trapped flux relaxation at the center of a single-domain Y-Ba-Cu-O superconductor upon pulsed field magnetization has been studied at T = 78 K. In the case of a weakly magnetized sample, the induction increases according to a logarithmic law and the creep rate (defined as S = −dlnB/dlnt) is negative. As the amplitude Ha of the magnetizing field grows, the creep rate decreases, changes sign, passes through a maximum, and tends to zero. The nonmonotonic behavior of S(Ha) is explained by a nonuniform radial distribution of the temperature during the magnetization pulse.

The break of shielding current at pulsed field magnetization of a superconducting annulus (experiment and model simulation)

During the pulsed field magnetization of a high-T c annulus in liquid nitrogen the shielding current drops abruptly, providing rapid penetration of the magnetic flux into the hole of the superconductor. After the break of current the trapped field in the hole is small and negative although the body of the annulus remains highly magnetized. In the present work the current breaking effect is investigated both experimentally and numerically. The influence of the pulse parameter on the shielding current evolution during the break is researched. A simple model for the qualitative description of this process is proposed. The model shows the development of heating localized on the inhomogeneity of the high-temperature superconductor annulus providing the formation of a high resistive channel with temperature near to T c. The appearance of this hot channel leads to the rapid reduction of the shielding current and presents a new scenario of flux jump at high temperature.

Magnetization of superconducting rings by long-duration pulses

After pulsed magnetization of the rings of high-temperature superconductors with a rectangular cross section, the magnitude of the trapped field has been measured depending on the decay time of the magnetization field. It has been shown that, by making use of the break of shielding current, one can magnetize the ring with a single pulse the rings to the maximum value corresponding to the field cooling process.