On a hollow superconducting sphere in a magnetic field

A system consisting of a single-domain ferromagnetic ball surrounded by a spherical superconducting shell and current-carrying wires wound on the shell is considered. The magnetic moment of the superconductor is calculated in terms of the London theory, in particular, for the case when the sum of the magnetic moments of the ball and system of currents is equal to a null vector.     

A superconducting vibrator with a trapped magnetic field

A design of a superconducting vibrator of bending oscillations is proposed. The magnetic-field dependence of the vibrator natural frequency is calculated. It is shown that, for the suggested construction, the natural frequency is tens of times more sensitive to the magnetic field than for all the resonators used before. It is proposed to use such a resonator to study the magnetic field penetrating into superconductors.     

On quark matter in a strong magnetic field

The effect of strong magnetic field on the bulk properties of quark matter is reinvestigated takingu, d ands-quarks as well as electrons in the presence of magnetic field. Here the bag pressure is chosen such that in the absence of magnetic field and at zero temperature the binding energy of theuds-system is <930 MeV while that ofud-system is greater than 940 MeV. It is observed that the equation of state changes significantly in a strong magnetic field. At finite temperature the electron chemical potential varies between 6 and 50 MeV. Thus the expansion of thermodynamical quantities in powers ofT/(Μ _i ² -M _v ⁽ⁱ⁾² )^1/2 is valid only up to few MeV. For high temperatures ∼40 MeV the exact integral expressions are to be taken.     

Anomalous currents in dense matter under a magnetic field

We consider fermionic dense matter under a magnetic field, where fermions couple minimally to gauge fields, and calculate anomalous currents at one loop. We find anomalous currents are spontaneously generated along the magnetic field but fermions only in the lowest Landau level contribute to anomalous currents. We then show that there are no more corrections to the anomalous currents from two or higher loops.     

Bulk viscosity of quark-gluon matter in a magnetic field

On the basis of low-energy QCD theorems, the bulk viscosity ζ(T, µ, H) is expressed in terms of basic thermodynamic quantities that characterizes quark-gluon matter at finite temperature and a finite baryon density in a magnetic field. Various limiting cases are considered.     

Phase boundary of the hexagonal—prism superconducting network in a magnetic field

In this paper, we systematically study the phase boundary T_c(\vec H) of a hexagonal-prism superconducting network in an external magnetic field \vec H of arbitrary magnitude and direction. The result indicates that the phase boundary of the hexagonal-prism superconducting circuit varies more sharply than that of the cubic circuit. The potential applications of the hexagonal-prism superconducting circuit are also discussed.     

Quantum tunneling between paramagnetic and superconducting states of a nanometer-scale superconducting grain placed in a magnetic field

We consider the process of quantum tunneling between the superconducting and paramagnetic states of a nanometer-scale superconducting grain placed in a magnetic field. The grain is supposed to be weakly coupled to a normal metallic contact that plays the role of the spin reservoir. Using the instanton method, we find the probability of the quantum tunneling process and express it in terms of the applied magnetic field, order parameter of the superconducting grain, and conductance of the tunneling junction between the grain and metallic contact.     

Retardation of charged particles by matter in a magnetic field

The Green's function of the steady transfer equation of charged particles in matter in the presence of a constant homogeneous magnetic field is found by the fifth-parameter method in the continuous-retardation approximation. The influence of the field on the particle penetration depth in matter is investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 13–15, July, 1991.     

Analysis of force characteristics of a superconducting ball in a given magnetic field

The electromagnetic force characteristics along Z direction of a superconducting ball levitated by spherical coils with shaping blocks are calculated based on a semi-analytical method. The calculating results from the semi-analytical method are compared with the finite element analysis (FEA) method through a calculation example. The method can be applied to further analysis of dynamic characteristics and parameter optimization in the suspension system.     

Hysteresis of critical currents of superconducting bridges in a weak magnetic field

Critical currents of indium and niobium bridges with constant thickness as well as granular aluminum bridges with constant thickness show hysteresis in a weak perpendicular magnetic field. It is found that the critical currents are determined by the pair-breaking mechanism.     

Critical state of a thin superconducting plate in an inclined magnetic field

A solution is obtained for the Bean critical-state model in an inclined magnetic field which leads to localization of the irreversible magnetic moment induced by the shielding currents. An experimental investigation of YBa₂Cu₃O_y single crystals and epitaxial films, and also plates of classical superconductors using vector magnetometry yields results fully consistent with the model calculations. The established geometric effects have an important influence on measurements of the angular dependence of the critical current and its anisotropy in a high-temperature superconductor. Zh. éksp. Teor. Fiz. 114, 273–290 (July 1998)     

Symmetric behavior of vortex states of superconducting networks in a magnetic field

We present magnetic field dependence of phase transition temperature and vortex configuration of superconducting networks based on theoretical study. The applied magnetic field is called “filling field” that is defined by applied magnetic flux (in unit of the flux quantum) per unit loop of the superconducting network. If a superconducting network is composed of very thin wires whose thicknesses are less than coherence length, the de Gennes–Alexander (dGA) theory is applicable. We have already shown that field dependences of transition temperature curves have symmetric behavior about the filling field of 1/2 by solving the dGA equation numerically in square lattices, honeycomb lattices, cubic lattices and those with randomly lack of wires networks. Many experimental studies also show the symmetric behavior. In this paper, we make an explicit theoretical explanation of symmetric behaviors of superconducting network respect to the applied field.     

Estimation of energy dissipated during superconducting wire motion in a magnetic field

An experiment was carried out to study the motion of superconducting wire under the influence of electromagnetic force. Experiments were conducted at 4.2 K by varying the experimental conditions such as tension to the superconducting wire, current ramp rate, and the use of different insulating materials at the interface of the superconducting wire. We were able to examine in detail the structure of the voltage spikes caused by sudden wire motion. The velocity of the wire motion, distance moved by the wire, and energy dissipated during wire motion are estimated.     

Levitation of a superconducting body in the field of N magnetic poles

Advanced magnetic technologies make it possible to create REE-based permanent magnets with a magnetic field sufficient for levitation. In this work, the feasibility of levitation in the field of arbitrarily (discretely or continuously) distributed magnetic poles is analyzed. A magnetic pole simulates a long and thin permanent magnet. The results obtained enable designing a levitator for an arbitrary distribution of magnets. A number of magnetic pole configurations is considered. The range of the levitator’s parameters providing stable equilibrium of the rotor in the magnetic field is found.     

多结超导环在外磁场中的行为

分析和计算了双结超导环在无偏置电流时的磁通、环流、自由能与外磁场的关系.发现双结环与单结环在磁场中的行为有所不同.当两个结的Ic相等时，双结环在1＜β=2πLIcΦ0＜2时，若无偏置电流，总磁通Φ、环流I与外磁通Φe的关系仍然是非回滞的曲线.仅当β≥2时，曲线才出现回滞.另外双结环有两支解，并且每支解的周期为2Φ0. 关键词： 双结环 双支解 2Φ0周期 回滞