共查询到20条相似文献,搜索用时 750 毫秒
1.
A. M. Bishaev A. A. Bush M. B. Gavrikov A. I. Denisyuk K. E. Kamentsev M. V. Kozintseva V. V. Savel’ev A. S. Sigov 《Technical Physics》2014,59(6):940-943
We consider the possibility of designing a plasma trap with a magnetic system formed by super-conducting rings and coils levitating in the field of a fixed coaxial coil carrying constant current. An analytic dependence of the potential energy of such a system with one or two levitating superconducting rings having trapped preset magnetic fluxes on their coordinates in the uniform gravitational field is obtained in the thin ring approximation. Calculations performed in the Mathcad system show that equilibrium states of such a system exist for certain values of parameters. Levitating states of a single superconducting ring and two superconducting rings in the field of the coil with constant current are observed experimentally in positions corresponding to calculated values. 相似文献
2.
A. I. Agafonov 《Physics of the Solid State》2011,53(8):1529-1539
A general expression for the cross section of inelastic magnetic scattering of cold polarized neutrons by superconducting
rings has been derived. In this scattering process, the metastable superconducting current changes via quantum jumps corresponding
to a decrease in the number of fluxoids in the superconducting ring by one or several units and the change in the energy of
the ring is transferred to the kinetic energy of the scattered neutron. For rings from type-II superconductors with a thickness
smaller than the field penetration depth but larger than the electron mean free path, the cross sections of inelastic scattering
with neutron spin flip have been obtained for the first time. The possibility of increasing the cross section of neutron scattering
by a system of rings has been discussed. 相似文献
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The possibility of observing persistent voltage in superconducting rings of different arm widths is experimentally investigated. It was previously found that switching of the arms between superconducting and normal states by an AC current induces DC voltage oscillation in the magnetic field with a period corresponding to the flux quantum inside the ring. We used systems with a large number of asymmetric rings connected in series to investigate the possibility of observing this quantum phenomenon near the superconducting transition, where thermal fluctuations lead to switching of ring segments without an external influence and the persistent current is much smaller than in the superconducting state. 相似文献
7.
A. I. Agafonov 《Physics of the Solid State》2012,54(8):1539-1553
The decay of a superconducting current in thin rings irradiated by a low-frequency coherent electromagnetic field has been predicted. Coherent oscillations induced in the superconducting condensate by this field lead to the emission of photons with the energy predominantly determined by discrete values of the energy of the superconducting ring. The thickness of the ring should be smaller than the skin depth of this field and than the London penetration depth. The discrete decay of the superconducting current accompanied by emission of one and two photons has been investigated for the first time. Numerical results have been presented for the angular and energy distributions of photons, as well as for the lifetime of the supercurrent states as a function of the size of the superconducting ring and the number of fluxoids in the initial state. 相似文献
8.
G. Q. Zha 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,84(3):459-466
The magnetic flux dependence of the vortex state for small mesoscopic superconducting
rings surrounded by a medium is investigated by the phenomenological Ginzburg-Landau
theory. The influences of the ring size and the surface superconductivity on the free
energy and total supercurrent are studied. For narrow rings, the persistent current
evolves towards a periodic behaviour with magnetic flux. The complete paramagnetic or
diamagnetic state, corresponding to positive or negative current flowing in the whole
ring, can occur. A remarkable intermittent superconducting behaviour for the ground-state
transition is found when the strength of surface-suppressed superconductivity is enlarged
or the ring size is decreased. Consequently, a pure superconducting state with positive
total current can be obtained. 相似文献
9.
This work presents a theoretical study of the energy spectrum of GaAs/AlGaAs concentric double quantum rings, under an applied magnetic field directed perpendicular to the ring plane. The Schrödinger equation for this system is solved in a realistic model consisting of rings with finite barrier potentials. Numerical results show that increasing the magnetic field intensity leads to oscillations in the ground state energy which, in contrast to the usual Aharonov-Bohm oscillations, do not have a well defined period, due to the coupling between inner and outer ring states. However, when one considers an elliptical geometry for the rings, the energy spectra of the inner and outer ring states are decoupled and the periodicity of the oscillations is recovered. 相似文献
10.
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
11.
M.G. BarseghyanAlireza Hakimyfard A.A. KirakosyanM.E. Mora-Ramos C.A. Duque 《Superlattices and Microstructures》2012,51(1):119-127
We consider the effects of electric and magnetic fields as well as of hydrostatic pressure on the donor binding energy in InAs Pöschl-Teller quantum rings. The ground state energy and the electron wave function are calculated within the effective mass and parabolic band approximations, using the variational method. The binding energy dependencies on the electric field strength and the hydrostatic pressure are reported for different values of quantum ring size and shape, the parameters of the Pöschl-Teller confining potential, and the magnetic field induction. The results show that the binding energy is an increasing or decreasing function of the electric field, depending on the chosen parameters of the confining potential. Also, we have observed that the binding energy is an increasing/decreasing function of hydrostatic pressure/magnetic field induction. Likewise, the impurity binding energy behaves as an increasing/decreasing function of the inner/outer radii of the quantum ring nanostructure. 相似文献
12.
M. V. Kozintseva A. M. Bishaev A. A. Bush M. B. Gavrikov K. E. Kamentsev N. A. Nizhel’skii V. V. Savel’ev A. S. Sigov 《Technical Physics》2017,62(6):890-894
The properties of short-circuited multiturn superconducting coils have been studied; coils with nonsuperconducting contacts have been fabricated from a high-temperature superconducting (HTSC) tape made by Super Power Company. The magnetic flux captured by HTSC coils has been measured at different values of magnetic field of the magnetizing solenoid. the critical current in the coils have been experimentally determined based on the maximum values of the field they captured. It is ~50% of the nominal value for this HTSC tape. The range of external magnetic field, where HTSC coils keep the captured magnetic flux, has been experimentally found. The obtained results have demonstrated the possibility of designing magnet systems with levitating coils made of HTSC tape, in which levitation is controlled without using feedbacks. 相似文献
13.
We present the theoretical investigation of spontaneous magnetization of a coupled 2×2 πring array. It is indicated by free energy calculation that the system has the lowest energy when the four π rings have the full antiparallel configuration. Furthermore, the numerical evaluation results show that the system which favours full antiparallel spontaneous magnetization is a quantum effect deriving from the phase cohering of the superconducting quantum wavefunctions in the four superconducting rings through the shared Josephson junctions. 相似文献
14.
F. Y. Alzoubi H. M. Al-khateeb M. K. Alqadi N. Y. Ayoub 《中国物理快报》2006,23(6):1641-1644
The problem of a small magnet levitating above a very thin superconducting disc in the Meissner state is analysed. The dipole-dipole interaction model is employed to derive analytical expressions for the interaction energy, levitation force, magnetic stiffness and frequency of small vibrations about the equilibrium position in two different configurations, i.e. with the magnetic moment parallel and perpendicular to the superconductor. The results show that the frequency of small vibrations decreases with the increasing levitation height for a particular radius of the superconducting disc, which is in good agreement with the experimental results. However, the frequency increases monotonically up to saturation by increasing the radius of the disc for a particular height of the magnet. In addition, the frequency of vibrations is higher when the system is in the vertical configuration than that when the system is in the horizontal configuration. 相似文献
15.
高温超导磁悬浮飞轮储能系统样机 总被引:1,自引:0,他引:1
在日益严峻的能源问题背景下,为展示无源高温超导磁悬浮技术在能量储存领域的应用前景,我们设计制作了一台全高温超导磁悬浮形式的飞轮储能样机.样机主要由高温超导磁悬浮轴承、飞轮转子、永磁电机和电路控制及负载部分组成.上下两个轴向型高温超导磁悬浮轴承用于悬浮和稳定飞轮转轴,直径200mm重量1.4kg的飞轮转子作为储能载体,最高可实现13000r/min的转速.在演示运行中,采用灯泡作为负载,该样机完成了从电能→机械能→电能的相互转换. 相似文献
16.
Cano D Kasch B Hattermann H Kleiner R Zimmermann C Koelle D Fortágh J 《Physical review letters》2008,101(18):183006
We report on the realization and characterization of a magnetic microtrap for ultracold atoms near a straight superconducting Nb wire with circular cross section. The trapped atoms are used to probe the magnetic field outside the superconducting wire. The Meissner effect shortens the distance between the trap and the wire, reduces the radial magnetic-field gradients, and lowers the trap depth. Measurements of the trap position reveal a complete exclusion of the magnetic field from the superconducting wire for temperatures lower than 6 K. As the temperature is further increased, the magnetic field partially penetrates the superconducting wire; hence the microtrap position is shifted towards the position expected for a normal-conducting wire. 相似文献
17.
Levitation and lateral forces between a point magnetic dipole and a superconducting sphere
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The dipole–dipole interaction model is employed to investigate the angular dependence of the levitation and lateral forces acting on a small magnet in an anti-symmetric magnet/superconducting sphere system. Breaking the symmetry of the system enables us to study the lateral force which is important in the stability of the magnet above a superconducting sphere in the Meissner state. Under the assumption that the lateral displacement of the magnet is small compared to the physical dimensions of our proposed system, analytical expressions are obtained for the levitation and lateral forces as a function of the geometrical parameters of the superconductor as well as the height, the lateral displacement, and the orientation of the magnetic moment of the magnet. The dependence of the levitation force on the height of the levitating magnet is similar to that in the symmetric magnet/superconducting sphere system within the range of proposed lateral displacements. It is found that the levitation force is linearly dependent on the lateral displacement whereas the lateral force is independent of this displacement. A sinusoidal variation of both forces as a function of the polar and azimuthal angles specifying the orientation of the magnetic moment is observed. The relationship between the stability and the orientation of the magnetic moment is discussed for different orientations. 相似文献
18.
M. Solaimani 《Optical and Quantum Electronics》2018,50(7):283
Here, we study the effects of the number of sites, quantum ring radius and potential well depth on the energy levels, persistent current, magnetic susceptibility and density of states (DOS) of a quantum ring with a quantum well within its circumstance in a magnetic flux perpendicular to its plane. We show that, for small radius quantum ring systems, there are periodic local gaps along the magnetic flux axis in the DOS plots and along the axis ‘energy’. For large radius quantum ring systems, a uniform gap along the energy axis exists and along the phi axis nothing changes. In quantum rings with a quantum well in their circumstance, by using the large confining potential, we can create uniform gaps in the Energy–phi plane. The energy eigenvalues, persistent current and magnetic susceptibility decrease by increasing the confining potential. A quantum ring even with a very small confining potential in its circumstance can sensibly decrease the persistent current and magnetic susceptibility, although it may do not change the energy eigenvalues and DOS maximum considerably. Thus, by using the abovementioned parameters, we are able to tune the DOS, persistent current, magnetic susceptibility and energy levels, desirably. 相似文献
19.
高温超导磁体在闭环运行时,可以提供稳定磁场,但是由于高温超导带材无法实现无阻焊接,成为高温超导磁体闭环运行的技术瓶颈.本文利用第二代高温超导带材制备闭环超导环,采用内部励磁和外部励磁对超导环进行励磁,在液氮温度中(77 K)测量超导环的中心俘获磁场.结果表明超导环在内部励磁俘获的磁场值比外部励磁俘获的磁场值高;外部励磁中,超导环中插入铁芯柱能提高俘获场;内部励磁中,超导环在螺线管闭环运行俘获的磁场值比开环运行俘获的磁场值高.结果对于高温超导闭环磁体励磁和高温超导带材磁通动力学研究具有很重要参考价值. 相似文献
20.
We show the existence of new stable ringlike localized scalar field configurations whose stability is due to a combination of topological and nontopological charges. In that sense these defects may be called semitopological. These rings are Noether charged and also carry Noether current (they are superconducting). They are local minima of the energy in scalar field theories with an unbroken U(1) global symmetry. We obtain numerical solutions of the field configuration corresponding to large rings and derive virial theorems demonstrating their stability. We also derive the minimum energy field configurations in 3D and simulate the evolution of a finite size Q ring on a three dimensional lattice. 相似文献