共查询到20条相似文献,搜索用时 15 毫秒
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V.R. Romanovskii K. Watanabe 《Physica C: Superconductivity and its Applications》2005,420(3-4):99-110
Static thermal and electric states before current instability in the current-carrying conductor like Bi-based superconducting composite are theoretically studied under the assumption that the critical current density of a superconductor and matrix resistivity are the non-linear functions of the temperature at fixed applied magnetic field. The simulation was made for the conduction-cooling conditions at different operating temperatures. The proposed analysis was based on the investigation of the non-isothermal voltage–current characteristics of composite superconductors. It is shown that they may have many-valued stable and unstable branches appearing in accordance with the non-trivial variation of the differential resistivity with increasing temperature. These states, first of all, are due to the temperature change of ∂Jc/∂T and are accompanied with the jump-like current-sharing mechanism. The parameters of the current instability onset as a function of operating temperature are numerically derived accounting for the additional stable branches of the voltage–current characteristics. In particular, it is revealed the existence of the static states when Bi-based composite superconductors may have a stable current distribution in the temperature range increasing up to the critical temperature of a superconductor without redistribution of all transport current into the matrix. The peculiarities of these phenomena are discussed. 相似文献
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The results from magnetooptical investigations of the remagnitization processes in composite film structures based on high-temperature superconductors in the temperature range of 4 to 80 K are presented. It is shown that the remagnetization of structures is due to the formation and propagation of wave of magnetic flux annihilation (areas with zero magnetic induction). The relationship between the penetration depth of annihilation front and the external magnetic field at different ambient temperatures, and the temperature dependence of the rate of motion of the front of magnetic flux annihilation, are found. The experimental data qualitatively fit the results from numerical calculations performed using the Monte Carlo method. 相似文献
4.
K. Guth V. Born Ch Jooss 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,42(2):239-245
Using space resolved magneto-optical microscopy we have studied the development of the critical state in high temperature superconducting small-angle grain boundaries in magnetisation experiments. It has been found that with respect to the position in the grain boundary plane this critical state develops in a highly inhomogeneous manner. Towards the centre of the grain boundary there exists a distinct suppression of the inter-granular currents flowing across the grain boundary. A strong correlation between the static (critical current) and the dynamical properties (e.g. electric field or flux-line velocity) of the vortex system inside the grain boundary appears to be the principal mechanism for the observed inhomogeneous current distribution in wide bi-crystalline current bridges.Received: 6 August 2004, Published online: 14 December 2004PACS:
74.25.Sv Critical currents - 74.72.Bk Y-based cuprates - 74.78.Bz High-T
c
films - 74.81.Bd Granular, melt-textured, amorphous and composite superconductors 相似文献
5.
N. Abdollahi J. Mahmoodi M. Abdollahi A.H. Ghorashi N. Alinejad 《Chinese Journal of Physics (Taipei)》2018,56(2):770-777
In this paper, an equivalent electrical circuit for response of a high-temperature superconductor (HTS) system for arbitrary time varying transport current is considered and as well as an analysis of the generated resistance losses is given. Also, for the pancake coil made with superconducting Bi-2223/AgMg tape, hysteresis behavior on the voltage-current curve is examined as a function of the current rate during ramp up and down at liquid nitrogen temperature. Behavior of voltage versus current is in good agreement with considered theory. 相似文献
6.
V. R. Romanovskii 《Technical Physics》2016,61(9):1352-1359
The influence of the transverse size of a composite wire based on a high-temperature superconductor on the dynamics of its thermoelectrodynamic properties at constant-rate current input has been studied. The physical mechanism behind the formation of stable regimes, which are characterized by the nonuniform distribution of the electric field and transport current over the cross-sectional area of the composite, has been determined. It has been shown that the critical current density of the superconducting composites determined from their current–voltage characteristic have lower and upper boundaries of electric voltages, which outline the allowable measurement range. It has been found that, when the input current completely penetrates into the composite, conditions for its stability are governed by the size effect. The essence of this effect is that conditions for current state stability in superconducting composites with the same cross-sectional area but various cross size differ. The conditions for the absence of unstable states in the composite the cross section of which is partially filled with the transport current have been formulated. 相似文献
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V. L. Gurtovoi A. A. Burlakov A. V. Nikulov V. A. Tulin A. A. Firsov V. N. Antonov R. Davis S. Pelling 《Journal of Experimental and Theoretical Physics》2011,113(4):678-682
The states of two phase-coupled superconducting rings have been investigated. Multiple current states have been revealed in
the dependence of the critical current on the magnetic field. The performed calculations of the critical currents and energy
states in a magnetic field have made it possible to interpret the experiment as the measurement of energy states into which
the system comes with different probabilities because of the equilibrium and nonequilibrium noises upon the transition from
the resistive state to the superconducting state. 相似文献
8.
Petrashov VT Chua KG Marshall KM Shaikhaidarov RSh Nicholls JT 《Physical review letters》2005,95(14):147001
Using the extraordinary sensitivity of Andreev interferometers to the superconducting phase difference associated with currents, we measure the persistent current quantum states in superconducting loops interrupted by Josephson junctions. Straightforward electrical resistance measurements of the interferometers give a continuous readout of the states, allowing us to construct the energy spectrum of the quantum circuit. The probe is estimated to be more precise and faster than previous methods, and can measure the local phase difference in a wide range of superconducting circuits. 相似文献
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The current-carrying capacity of a wide high-temperature superconducting film under conditions of rapid injection of current is investigated theoretically. An analytic expression is derived for the rate of current injection into the film at which a marked degradation of the current-carrying capacity of the film occurs. The obtained results may be important from the standpoint of analyzing the stability of superconducting ac devices. 相似文献
10.
M. I. Petrov D. A. Balaev S. V. Ospishchev K. A. Shaikhutdinov B. P. Khrustalev K. S. Aleksandrov 《Physics of the Solid State》1997,39(3):362-368
Composites are prepared from a high-temperature superconductor with the 1-2-3 structure and the low-temperature oxide BaPb3/4Bi1/4O3 with various volume concentrations of the high-temperature and low-temperature superconductors. The temperature dependences
of the electrical resistivities and critical current densities of the composites are measured. It is shown experimentally
that these composites comprise a synthetically created network of Josephson weak links (with a specified degree of coupling).
Fiz. Tverd. Tela (St. Petersburg) 39, 418–424 (March 1997)
Deceased. 相似文献
11.
R. Gonczarek 《Applied Physics A: Materials Science & Processing》1988,47(2):111-113
Applying the Jing and Gonser model for the high-T
c superconductivity based on electron hopping the Stoichiometric connections and appropriate restrictions are given. It is shown that for the compounds of typeA
2–x
B
xCuO4 andAB
2Cu3O9–x, whereA is a trivalent rare-earth ion andB is a divalent alkali earth ion, the superconductivity is realized only if 0T
c superconducting compounds are propounded and considered, too. The optimum compound which contains fluorine atoms should be of the form YBa2Cu3F2O5.875. All the relations presented find confirmation in experiments. 相似文献
12.
The current instability is studied in high-temperature superconducting current-carrying elements with I–V characteristics described by power or exponential equations. Stability analysis of the macroscopic states is carried out in terms of a stationary zero-dimensional model. In linear temperature approximation criteria are derived that allow one to find the maximum allowable values of the induced current, induced electric field intensity, and overheating of the superconductor. A condition is formulated for the complete thermal stabilization of the superconducting composite with regard to the nonlinearity of its I–V characteristic. It is shown that both subcritical and supercritical stable states may arise. In the latter case, the current and electric field intensity are higher than the preset critical parameters of the superconductor. Conditions for these states depending on the properties of the matrix, superconductor’s critical current, fill factor, and nonlinearity of the I–V characteristic are discussed. The obtained results considerably augment the class of allowable states for high-temperature superconductors: it is demonstrated that there exist stable resistive conditions from which superconductors cannot pass to the normal state even if the parameters of these conditions are supercritical. 相似文献
13.
V. R. Romanovskii 《Technical Physics》2017,62(4):560-568
The conditions of the occurrence and development of thermal instabilities in the composite superconductor with a continuously increasing current-voltage characteristic, which is described by the power equation, have been studied. The conditions for thermal stabilization have been analyzed in the general form using dimensionless variables that keep their invariance when varying. For the local temperature disturbance, the critical energies and velocities of its irreversible propagation have been calculated. It has been proved that composites superconductors can have stable states, when the ultimate currents can be higher or lower of the conventionally preset critical current of the composite. Furthermore, superconductivity destruction at supercritical currents takes place not in the form of a stepwise transition from the superconducting to normal state, but due to the formation of thermal and electric switching waves that propagate along the composite superconductor with a constant speed. The condition for full thermal stabilization has been formulated for the superconducting composites with a power current–voltage characteristic. The results of the numerical experiments have proved that the existing theory of thermal stabilization, which assumes a stepwise superconducting–normal transition, leads to the considerable limitation of the range of the stable currents, at which a superconducting state can be kept. 相似文献
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V. R. Romanovskii 《Doklady Physics》2016,61(8):377-383
The physical features of the formation of macroscopic states of superconducting composites consisting of a superconductor and a coating under flux creep are discussed. It is demonstrated that there exist characteristic electric field strengths depending on the properties of the superconductor, cooling conditions, and characteristics of the stabilizing coating, which affect the intensity of the E-I characteristics of the superconducting composites. Analysis shows that the measurements of the critical properties of superconductors can be accompanied by a nonuniform electric field distribution over the composite cross section and high stable superheating of the superconductor, which do not lead to superconductivity breaking. 相似文献
17.
J.A. Lorenzo-Fernández M.R. Osorio M.J. Tello 《Journal of Physics and Chemistry of Solids》2010,71(8):1105-1107
Fault current limiters are one of the most promising applications of high-temperature superconductors. Two important and interrelated aspects of these devices are their thermal behaviour and their refrigeration. Here we will present some results of our recent researches about this topic concerning the possibility of using superconducting thin-film microbridges as very efficient microlimiters intended to operate at very low powers as could be superconducting microelectronics applications (SQUID based electronics, infrared detectors, etc.). 相似文献
18.
O. A. Shevchenko J. J. Rabbers A. Godeke B. ten Haken H. H. J. ten Kate 《Physica C: Superconductivity and its Applications》1998,310(1-4):106-110
In a typical superconducting coil made of BSCCO/Ag tape, both amplitude and direction of the magnetic field determine the critical current, resistive voltage and AC loss. The distribution of the magnetic field along and across the superconducting tape in a coil is rather complex. This gives rise to the question: how accurate can one predict the critical current, V–I characteristic and AC loss of the AC coil from results of short sample measurements? To answer this question, we have measured and compared the characteristics of a short sample and a small coil employing 14 m of the same tape at 77 K. The comparison is performed as follows. First, a short sample is characterised with regard to the field dependence of the critical current, V–I characteristic and the AC loss. Second, the distribution of the magnetic field along the tape in a coil is accurately calculated. From the data, the voltage along the tape and the loss of the tape in the coil are found. Finally, the resistive voltage and the AC loss of the complete coil are calculated and compared to measured AC losses in the frequency range of 0 to 160 Hz, typical for power applications. 相似文献
19.
The energy bands and the global density of states are computed for
superconductor / normal-metal superlattices in the clean limit.
Dispersion relations are derived for the general case of insulating
interfaces, including the mismatch of Fermi velocities and effective
band masses. We focus on the influence of finite interface
transparency and compare our results with those for transparent
superlattices and trilayers. Analogously to the rapid
variation on the atomic scale of the energy dispersion with
layer thicknesses in transparent superlattices, we find strong
oscillations of the almost flat energy bands (transmission
resonances) in the case of finite transparency. In small-period
transparent superlattices the BCS coherence peak disappears and a
similar subgap peak is formed due to the Andreev process. With
decreasing interface transparency the characteristic double peak
structure in the global density of states develops towards a gapless
BCS-like result in the tunnel limit. This effect can be
used as a reliable STM probe for interface transparency. 相似文献