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1
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Dynamics of Thermomagnetic Avalanches in Melt-Textured YBaCuO Superconductors

100%
Nabiałek A., Vasiliev S., Aleksyeyev P., Chabanenko V.
Acta Physica Polonica A
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2007
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vol. 111
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issue 1
153-158
EN
We investigated dynamics of the thermomagnetic avalanche development in melt-textured samples of the oxide YBaCuO high temperature superconductor. We found that the flux jumps, caused by the thermomagnetic instabilities, are accompanied by giant convergent oscillations of the surface induction. These results are compared with the dynamics of the flux jumps in other type-II superconductors, including conventional NbTi and oxide high temperature Bi _2Sr_2CaCu_2O_{8+δ} superconductor, and discussed in the framework of the available model of the thermomagnetic avalanche development.
2
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The Influence of Fast Neutron Irradiation on the Magnetostriction of Ceramic YBa_2Cu_3O_{7-δ} Sample

88%
Nabiałek A., Vasiliev S., Pytel B., Chabanenko V., Piechota S.
Acta Physica Polonica A
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2004
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vol. 106
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issue 5
739-744
EN
We investigated the magnetostriction of ceramic YBa_2Cu_3O_{7-δ} sample both before and after fast neutron irradiation with the fluency of 7.55×10^{17} n/cm^2 and energy of above 0.5 MeV. We have found that after irradiation the widths of both transverse and longitudinal magnetostriction hysteresis loops at a given temperature and at a given external magnetic field increased several times. At 4.2 K and in 10 tesla the widths of the magnetostriction hysteresis loop of the irradiated sample are of an order of 10^{-5}. The results can be understood in the framework of the model of the magnetostriction induced by the pinning forces, assuming the stress in the sample to be induced mainly by the intragrain screening currents.
3
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Stability of Bilayer Superconductors against Thermomagnetic Avalanche

88%
Vasiliev S., Chumak O., Chabanenko V., Pérez-Rodríguez F., Nabiałek A.
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EN
The problem of stability of bilayer type II superconductor with different critical current densities of inner part and coating was considered. The optimum thickness of surface layer enabling the maximal increase of the field of first flux jump was found. The field of instability for such bilayer structure was calculated for NbTi superconductor. An increase of the field of the first flux jump by about 60% has been found for optimal coating thickness.
4
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Moderation of the Flux Jumps Dynamics by Eddy-Currents in a Disk Shape NbTi Superconductor

76%
Vasiliev S., Chabanenko V., Nabiałek A., Rusakov V., Piechota S., Szymczak H.
Acta Physica Polonica A
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2004
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vol. 106
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issue 5
777-783
EN
We studied the moderation of the flux jumps dynamics in a disc shape NbTi-50% superconductor caused by eddy-currents induced in two copper cylinders attached to both surfaces of the investigated sample. We investigated experimentally the time of the flux jump duration, amount of the magnetic flux entering the sample during the jump as well as the fine structure of the jumps as a function of temperature and the external magnetic field. A simple theoretical model, which describes the magnetic field dependence of the amount of the magnetic flux entering the superconducting sample during the flux jump, was developed.
5
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The Structure of Thermomagnetic Avalanches in Superconducting Disc of NbTi

76%
Vasiliev S., Nabiałek A., Chabanenko V., Rusakov V., Piechota S., Szymczak H.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
661-668
EN
We investigated dynamics of giant flux jumps, caused by thermomagnetic avalanches, in superconducting disc of conventional NbTi-50% superconductor. We studied surface magnetization, as well as changes of magnetic flux in the superconducting sample and in the area around it. The influence of the magnetic history on the flux jumps structure was investigated. The most complex structure of the flux jumps was found during sample remagnetization. The comparison between dynamic changes of the magnetic flux in the sample and in the area around it shows that, at the last stage of the thermomagnetic avalanche, a process of magnetic flux redistribution in the superconductor's volume occurs. This process is not accompanied by an entrance of additional flux lines into the superconductor's volume.
6
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Obtaining a Rough Flux Front in Type-II Superconductors Using a Critical State Model

76%
Romero-Salazar C., Hernández-Flores O., Chabanenko V., Kuchuk E., Abaloszewa I., Nabialek A., Pérez-Rodríguez F.
Acta Physica Polonica A
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2016
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vol. 130
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issue 2
645-648
EN
In this work we numerically modelled a periodic magnetic flux pattern which qualitatively reproduces the so-called sand avalanches scenario in type-II superconductors. To model these sand-pile patterns we consider a perturbation on the critical current which, as a first approximation, follows a periodic function which depends on the position.
7
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The Influence of the Sample Shape on the Flux Jumps Dynamics in Conventional NbTi Superconductor

76%
Nabiałek A., Piechota S., Szymczak H., Vasiliev S., Chabanenko V., Rusakov V.
Acta Physica Polonica A
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2008
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vol. 114
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issue 1
235-241
EN
We investigated giant flux jumps, caused by thermomagnetic avalanches, in two cylindrical samples of conventional NbTi-50% superconductor of the same diameter -- 14 mm, but of different heights -- 4 mm and 20 mm. We studied the influence of demagnetizing effects on the flux jumps occurrence, the amount of the magnetic flux entering the sample during the following jumps and on the flux jumps dynamics. The dynamics of the magnetic flux entering the sample is compared with the dynamics of the stray field.
8
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Critical State Stability and Flux Jumps' Dynamics in a Single Crystal of YBa_{2}Cu_{3}O_{7-δ }

76%
Nabiałek A., Vasiliev S., Chabanenko V., Yao X., Cai Y., Guo L., Kuzovui M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
836-840
EN
We studied the critical state stability and the dynamics of the flux jumps, caused by thermomagnetic avalanches, in a large (3× 3× 1 mm^{3}) single crystal of YBa_{2}Cu_{3}O_{7-δ } superconductor. Flux jumps were observed only at the lowest temperatures attainable in our system (at about 2.2 K) and for the external magnetic field parallel to the c-axis of the investigated crystal. It is shown that thermomagnetic avalanches are initiated in dynamic conditions, for which the magnetic diffusivity is much smaller than the thermal diffusivity. For large single crystals of YBa_{2}Cu_{3}O_{7-δ } immersed directly in liquid helium, the analysis of the critical state stability can be performed in isothermal approximation. However, the conditions of the critical state stability can change dramatically by improving the thermal isolation between the sample and the surrounding coolant. The dynamics of the flux jumps was analyzed in the framework of the model of magnetic diffusion. It is shown that the magnetic diffusivity changes dramatically during the process of the thermomagnetic avalanche. We also studied the influence of the external magnetic field and of the magnetic history on the duration of the flux jumps.
9
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The Influence of Magnetic History on the Stability of Critical State and the Dynamics of Flux Jumps in Conventional NbTi Superconductor

76%
Nabiałek A., Vasiliev S., Chabanenko V., Perez-Rodriguez F., Piechota S., Szymczak H.
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issue 2
343-345
EN
We studied the influence of magnetic history on the stability of critical state and the dynamics of flux jumps in conventional NbTi superconductor. We have found that both the stability of critical state and the dynamics of flux jumps are strongly influenced by the magnetic history and by the magnetic field distribution induced within the sample by preceding jumps. This magnetic field distribution can be particularly complex in the region of the hysteresis loop where the external magnetic field changes its sign (region of remagnetization), because of demagnetizing effects. For this reason, the most complex structure of the flux jumps is observed in the third quadrant of magnetization hysteresis loop. Flux jumps observed in the region of remagnetization have different dynamics in comparison to the jumps observed in other regions of the magnetization hysteresis loop. Duration of these jumps is usually significantly longer than others, and their structure is more complex.
10
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The Influence of the Magnetic Field on the Dynamics of the Flux Jumps in the Flux Flow Model

76%
Vasiliev S., Nabiałek A., Rusakov V., Belevtsov L., Chabanenko V., Szymczak H.
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issue 2
340-342
EN
We studied the dynamics of the flux jumps in type II superconductors assuming this dynamics to be determined by magnetic diffusion. The conductivity of the sample during the jump was described by the flux flow conductivity, which depends on local magnetic field. We solved this problem numerically for an infinite slab sample. We assumed that superconducting sample was fully penetrated by the magnetic flux at the beginning and that the local induction of the magnetic field, in the whole sample, was equal to B_0. Then, the external magnetic field was increased by a value of ΔB_{a} and in the external magnetic field of B_0 + ΔB_{a} flux jump occurred. In our simulations we used the parameters characteristic of a conventional NbTi superconductor at 4.2 K. In particular, we studied the influence of the parameter B_0 on the flux jumps' dynamics. We have found that this parameter strongly influences initial stage of the diffusion process. With increasing B_0, the time during which flux front of the avalanche reaches the center of the sample decreases. The results of numerical simulations were compared with experiments.
11
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Giant Magnetostriction Jumps in Conventional NbTi Superconductor

76%
Nabiałek A., Vasiliev S., Chabanenko V., Aleksyeyev P., Rusakov V., Piechota S., Szymczak H.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
633-639
EN
Magnetostriction of a large slab of conventional NbTi superconductor, with a diameter of about 6 mm, was investigated by the strain gauge technique. At the temperature of 4.2 K and in the external magnetic field of several T we found irreversible magnetostriction of an order of 10^{-5}, where the number means the relative changes of the slab diameter. This large magnetostriction is accompanied by giant magnetostriction jumps, caused by thermomagnetic avalanches. These thermomagnetic avalanches also cause giant jumps of the surface magnetization, which can be observed by using the Hall probes. The results were analyzed in the framework of the pinning induced magnetostriction model.
12
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Oscillating Dynamics and Trajectory of the Single Vortex Line

76%
Rusakov V., Vasiliev S., Chabanenko V., Yurov A., Nabiałek A., Piechota S., Szymczak H.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
641-646
EN
The De Gennes and Matricon problem of finding the spectrum of oscillations of massive vortex line under the action of pinning and viscosity forces is solved. The obtained vibration spectrum of the vortex is discussed and the role of each contributing force is elucidated. The trajectory of the vortex motion is calculated and illustrated.
13
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Size Effect in Impedance of Nb_3Al Superconductor

64%
Aleksyeyev P., Nabiałek A., Vasiliev S., Rusakov V., Chabanenko V., Zalutskii M., Piechota S., Szymczak H., Kodess B.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
555-559
EN
We present the results of the impedance measurements in Nb_3Al superconducting polycrystalline alloy vs. temperature and magnetic field. Using these results and applying the size effect model we calculate the flux-flow conductivity of the Nb_3Al superconducting alloy near its critical temperature.
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