The pulsed field magnetization (PFM) of drilled along c-axis stacks and laser cut tape-slit magnets (TSM) made of high-temperature superconducting tapes of the second generation (HTS-2G) was researched at boiling point of liquid nitrogen. The change of electromagnetic properties at variation of bore’s diameter in the stack of tapes drilled along c-axis was examined. The results of measurement of the screening current evolution during the magnetization and the relaxation of residual magnetic fields are presented. The curves of the induced current dependence on the applied field are presented. The trapped field dependence on the applied field amplitude was examined for both cases. The distribution of the residual field after the magnetization of the stack is measured. The problem of heating of composite structures by a pulsed magnetic field and heat transfer between composite layers was considered. A comparative analysis with the results of experiments on pulsed magnetization of single-domain HTS bulk annuli was performed.

A magnetic field relaxation at the center of a pulse-magnetized single-domain Y-Ba-Cu-O superconductor at 78K has been studied. In case of a weak magnetization, the magnetic flux density increases logarithmically and normalized relaxation rate defined as S=-d(lnB)/d(lnt) is negative (S=-0.037). When an external magnetic field magnitude increases, the relaxation rate first decreases in absolute value, then changes sign (becomes positive, S>0) and after reaching some maximum finally reduces to a very small value. Non-monotonous dependence of S vs Ha is explained by a non-homogeneous local temperature distribution during a pulse magnetization.

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 = − d ln B/d ln t ) is negative. As the amplitude H a of the magnetizing field grows, the creep rate decreases, changes sign, passes through a maximum, and tends to zero. The nonmonotonic behavior of S ( H a ) is explained by a nonuniform radial distribution of the temperature during the magnetization pulse.

The experimental results of curling effect investigation (sharp increasing of the normal phase propagation speed under influence of the magnetic flux avalanche) in superconducting Nb-Ti and Nb-Zr wires are presented. The external magnetic field was imposed parallel to an axis of a sample of a superconducting wire by thickness from 0.16 mm up to 0.30 mm without a normal stabilizing covering, the transport current was put, and after initiation of a normal phase on a short part of a sample the normal phase propagation and the magnetic flux avalanche along a sample were registered simultaneously. It was found, that the thickness of the magnetic flux avalanche L-mfa and the thickness of the normal phase front L-npf (length of the part of a sample engaged by S-N transition) achieves 3-4 mm, that is more than 10 diameters of the sample. The heating of a superconducting wire by the magnetic flux avalanche is accompanied by increase of the speed of normal phase propagation V-npp. In a narrow range of change of a transport current the sharp increasing of the speed of normal phase propagation V-npp up to the speed of a magnetic flux avalanche V-mfa occurs. The further increasing of a transport current is accompanied by reduction of a distance (spacing) between the normal phase and the magnetic flux avalanche. In turn V-mfa increase with increasing of critical current dencity J(c) and thickness of a superconducting wire. In particular the speeds V-mfa and V-npp achieve the value 9-13 km/s for the wire Nb-25%Zr by thickness of 0.24 mm with the critical current J(c) = 2-4 MA/cm(2) in magnetic fields 0.5-1 T.

Steady state propagation of a magnetic perturbation along a monofilament superconducting wire in circumstances of thermomagnetic instability was investigated. At temperature T=4.2K and magnetic field B=0.5-0.7T the propagation velocity is v = 2.5 - 3.5 km/sec in NbTi wire and this one exceeds a 9 km/sec in NbZr wire.

Magnetic flux flow in layered NbTi/Nb and textured superconducting ceramics Bi2Sr2CaCu2O8+d with the nearly reversible magnetization curve are measured. The characteristic time of the magnetic moment relaxation of such superconductors is determined by the viscous flux flow. It is observed, that in a parallel to superconducting layers external magnetic field the characteristic time of the magnetic flux inflow into the sample and the time of the flux outflow from the sample differ in several times. This difference in the characteristic times is unequivocally due to the flux flow into the sample through the end plates of the thin superconducting layers (plates), where Bean-Livingston barrier is effectively suppressed, but the flux flow out from the superconducting layers (plates) through the wide sides of the plates freely. The experimental proof of the barrier absence for the outflow of the magnetic flux on the border of the superconductor is received. Thus is shown, that the border (surface) of the type-II superconductor is the "semiconductor" for the magnetic flow: it lets the flux to flow out from the superconductor freely, but it interferes with the flux to flow into the superconductor.

The tuning of the magnetic fluxes to the pinning structure oriented along superconducting filaments is the reason of the existence of the magnetic field component Bperpendicular to perpendicular to the external magnetic field H. The dependence Bperpendicular to from the value and the orientation of an external magnetic field H is measured for multifilamentary NbTi sample. The flux capture by the pinning structure is observed when an external magnetic field is almost parallel to filaments. The dependence Bperpendicular to from the external magnetic field value allows estimating the pinning structure scale of the superconductor.

The sonic range velocities of normal zone propagation in high current density superconductor were observed. The experimental results were obtained on samples of 0.16–0.11 mm thickness of a monofilamentary NbTi wire with critical current density J c about 10 6 A/cm 2 . The s→n change of the sample sections was recorded after the normal zone stimulation by the magnetic field impulse. The voltage increasing speed reached 1.5×10 7 V/s, and the normal zone propagation velocity exceeded 5±1 km/s. This high velocity can be caused by the detonation-like propagation of normal phase in superconductor with high current density.

The feasibility of utilization of cold switches for quench protection of very large superconducting magnets (e.g., for SMES) is considered. The scheme of quench protection of large SMES is suggested. The necessary number of sections can be easily evaluated. Destructive superconducting switches seem to be the best solution. The switch has to be properly designed to avoid arcing and to offer a possibility to change the destructive elements in a reasonable time without warming up large portions of the winding. A suggestion is also made to make use of the temperature dependence of the electrical resistance of the dump resistor. A proper choice of its mass can result in 25 percent decrease of a quench load.<>