The interphase surface energy in some pure and impure superconductors

1960 ◽  
Vol 255 (1282) ◽  
pp. 407-426 ◽  
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Surface Energy ◽  
Detailed Analysis ◽  
Energy Parameter ◽  
Transverse Magnetic ◽  
Superconducting Phase ◽  
Interphase Surface ◽  
Dilute Alloys ◽  
The Magnetic Field

A new method has been developed for obtaining relative values of the surface energy parameter, Δ, in superconductors. It involves the measurement of the resistance of thin films subjected to a transverse magnetic field. The method has been applied to tin, indium and aluminium and to dilute alloys of the first two. The principal new results are that Δ is 1⋅48 times larger in indium than in tin and that the addition of impurity to either metal lowers Δ without changing the nature of its temperature dependence. These conclusions are compared with current theories of the interphase surface energy. An attempt has been made to deduce the absolute magnitude of Δ, which requires a detailed analysis of the way in which the last traces of the superconducting phase are eliminated from the film by the action of the magnetic field. The analysis is necessarily over-simplified but it does give a figure for Δ in pure tin which is reasonably consistent with the previous estimates of Faber and Sharvin.

The phase transition in superconductors II. Phase propagation above the critical field

1953 ◽  
Vol 219 (1136) ◽  
pp. 75-88 ◽  
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Relaxation Time ◽  
Surface Energy ◽  
Field Strength ◽  
Eddy Currents ◽  
Superconducting Phase ◽  
Interphase Surface ◽  
Electromagnetic Damping ◽  
Phase Propagation

Detailed measurements have been made of the rate at which the superconducting phase collapses radially in cylindrical rods of tin, when they are suddenly subjected to a magnetic field greater than the critical. This is probably the simplest example of phase propagation in superconductors. The results in most respects confirm the theory of Pippard (1950 a ) and Lifshitz (1950), according to which the propagation is controlled by an electromagnetic damping associated with the setting up of eddy currents. This theory explains in detail the way in which the rate of propagation depends on specimen radius and conductivity, and on field strength; its only failure is at the higher temperatures, where the magnitude of the rate of propagation tends to be slightly less than the theory predicts. Other factors besides eddy currents which might be retarding the transition are latent heat, the interphase surface energy, and a finite relaxation time governing the destruction of superconductivity by a magnetic field; but none of these proves altogether adequate to account for the discrepancy mentioned. The experiments provide evidence that the relaxation time is less than 2 x 10 -7 s in tin.

scholarly journals Enhanced X-ray emission arising from laser-plasma confinement by a strong transverse magnetic field

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Evgeny D. Filippov ◽  
Sergey S. Makarov ◽  
Konstantin F. Burdonov ◽  
Weipeng Yao ◽  
Guilhem Revet ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic ◽  
Radiative Properties ◽  
Magnetic Field Direction ◽  
Solid Target ◽  
Total Plasma ◽  
Plasma Confinement ◽  
X Ray ◽  
Magnetic Compression ◽  
The Magnetic Field

AbstractWe analyze, using experiments and 3D MHD numerical simulations, the dynamic and radiative properties of a plasma ablated by a laser (1 ns, 10$$^{12}$$ 12 –10$$^{13}$$ 13 W/cm$$^2$$ 2 ) from a solid target as it expands into a homogeneous, strong magnetic field (up to 30 T) that is transverse to its main expansion axis. We find that as early as 2 ns after the start of the expansion, the plasma becomes constrained by the magnetic field. As the magnetic field strength is increased, more plasma is confined close to the target and is heated by magnetic compression. We also observe that after $$\sim 8$$ ∼ 8  ns, the plasma is being overall shaped in a slab, with the plasma being compressed perpendicularly to the magnetic field, and being extended along the magnetic field direction. This dense slab rapidly expands into vacuum; however, it contains only $$\sim 2\%$$ ∼ 2 % of the total plasma. As a result of the higher density and increased heating of the plasma confined against the laser-irradiated solid target, there is a net enhancement of the total X-ray emissivity induced by the magnetization.

Magnetism of CoFe2O4 thin films annealed under the magnetic field

2015 ◽  
Vol 394 ◽  
pp. 287-291 ◽  
Author(s):  
Y.Q. Dai ◽  
J.M. Dai ◽  
X.W. Tang ◽  
Z.F. Zi ◽  
K.J. Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
The Magnetic Field

scholarly journals Heat Transfer to MHD Oscillatory Viscoelastic Flow in a Channel Filled with Porous Medium

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Rita Choudhury ◽  
Utpal Jyoti Das
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Porous Medium ◽  
Radiative Heat ◽  
Saturated Porous Medium ◽  
Transverse Magnetic ◽  
Viscoelastic Flow ◽  
Viscoelastic Parameter ◽  
Flow Parameters ◽  
The Magnetic Field

The combined effect of a transverse magnetic field and radiative heat transfer on unsteady flow of a conducting optically thin viscoelastic fluid through a channel filled with saturated porous medium and nonuniform walls temperature has been discussed. It is assumed that the fluid has small electrical conductivity and the electromagnetic force produced is very small. Closed-form analytical solutions are constructed for the problem. The effects of the radiation and the magnetic field parameters on velocity profile and shear stress for different values of the viscoelastic parameter with the combination of the other flow parameters are illustrated graphically, and physical aspects of the problem are discussed.

STUDY OF PHASE PROPAGATION IN SUPERCONDUCTING ALUMINUM BY ULTRASONIC ATTENUATION MEASUREMENTS

1959 ◽  
Vol 37 (5) ◽  
pp. 614-618 ◽  
Author(s):  
K. L. Chopra ◽  
T. S. Hutchison
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Ultrasonic Attenuation ◽  
Cylindrical Specimen ◽  
Current Theory ◽  
Superconducting Phase ◽  
Rate Of Change ◽  
Time Rate ◽  
Phase Propagation ◽  
The Magnetic Field

The phase propagation in superconducting aluminum has been studied by measuring the time rate of change of ultrasonic attenuation. The time taken for the destruction of the superconducting phase in a cylindrical specimen, by means of a magnetic field, H, greater than the critical field, Hc, is approximately proportional to{H/(H–Hc)} in agreement with eddy-current theory. In the converse case, where the superconducting phase is restored by switching off the magnetic field H (>Hc), the total time taken is nearly independent of the temperature (or Hc) as well as H. The superconducting phase grows at a non-uniform volume rate which is considerably less than the uniform rate of collapse.

scholarly journals Вращение плазменной струи высокочастотными электромагнитными полями и ее использование для масс-сепарации

2020 ◽  
Vol 90 (3) ◽  
pp. 482
Author(s):  
Н.М. Горшунов ◽  
Е.П. Потанин
Keyword(s):  
Magnetic Field ◽  
Spent Nuclear Fuel ◽  
Transverse Magnetic ◽  
Mhd Equations ◽  
Direct Flow ◽  
Fuel Component ◽  
Product Flow ◽  
Dipole Configuration ◽  
Uranium Plutonium ◽  
The Magnetic Field

Equations are obtained that describe the characteristics of the azimuthal motion and radial expansion of a plasma jet under the action of a rotating transverse magnetic field of a dipole configuration in a longitudinal static magnetic field. The analysis was carried out both in the multicomponent approximation and on the basis of MHD equations taking into account the Hall effect. Based on the obtained dependences of the azimuthal and radial ion velocities on the magnetic field values, the separation characteristics of the direct-flow plasma centrifuge are estimated for the separation of a two-component binary mixture simulating spent nuclear fuel. It was shown that the concentration of the heavy uranium-plutonium component in the product flow can be increased from the initial 96 to 99.8% with a fuel component extraction of 0.87.

scholarly journals Spatial Temperature Profile in a Magnetised Capacitively Coupled Discharge

2018 ◽  
Vol 16 (6) ◽  
pp. 385-390
Author(s):  
Shikha BINWAL ◽  
Jay K JOSHI ◽  
Shantanu Kumar KARKARI ◽  
Predhiman Krishan KAW ◽  
Lekha NAIR ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electron Temperature ◽  
Temperature Profile ◽  
Transverse Magnetic ◽  
Capacitively Coupled ◽  
Particle In Cell ◽  
Cell Simulation ◽  
Higher Temperature ◽  
The Magnetic Field ◽  
Emissive Probe

A floating emissive probe has been used to obtain the spatial electron temperature (Te) profile in a 13.56 MHz parallel plate capacitive coupled plasma. The effect of an external transverse magnetic field and pressure on the electron temperature profile has been discussed. In the un-magnetised case, the bulk region of the plasma has a uniform Te. Upon application of the magnetic field, the Te profile becomes non-uniform and skewed.  With increase in pressure, there is an overall reduction in electron temperature. The regions adjacent to the electrodes witnessed a higher temperature than the bulk for both cases. The emissive probe results have also been compared with particle-in-cell simulation results for the un-magnetised case.

scholarly journals Теплообмен при смешанной конвекции расплава соли в присутствии магнитных полей

2019 ◽  
Vol 45 (10) ◽  
pp. 27
Author(s):  
И.А. Беляев ◽  
Д.А. Бирюков ◽  
А.В. Котляр ◽  
Е.А. Белавина ◽  
П.А. Сардов ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Temperature Fluctuations ◽  
Reynolds Numbers ◽  
Transverse Magnetic ◽  
Statistical Characteristics ◽  
Transfer Coefficients ◽  
Gravitational Flow ◽  
Heat Transfer Coefficients ◽  
The Magnetic Field

The results of an experimental study of the salt melt downflow in a uniformly heated pipe under the influence of a strong transverse magnetic field are presented. The changes of heat transfer coefficients and statistical characteristics of temperature fluctuations under the influence of the magnetic field are investigated. The peculiarities of the transition of the viscous-gravitational flow in the viscous-inertial-gravitational flow at Reynolds numbers (Re=3000-5000) under the influence of the magnetic field (Ha=17) were studied.

The magnetic field about a three-dimensional block neodymium magnet

2021 ◽  
Vol 62 ◽  
pp. 386-405
Author(s):  
Graham John Weir ◽  
George Chisholm ◽  
Jerome Leveneur
Keyword(s):  
Magnetic Field ◽  
Permanent Magnets ◽  
Hard Disk Drives ◽  
Three Dimensional ◽  
Transverse Magnetic ◽  
Observation Point ◽  
Magnetization Direction ◽  
Potential Approach ◽  
Neodymium Magnet ◽  
The Magnetic Field

Neodymium magnets were independently discovered in 1984 by General Motors and Sumitomo. Today, they are the strongest type of permanent magnets commercially available. They are the most widely used industrial magnets with many applications, including in hard disk drives, cordless tools and magnetic fasteners. We use a vector potential approach, rather than the more usual magnetic potential approach, to derive the three-dimensional (3D) magnetic field for a neodymium magnet, assuming an idealized block geometry and uniform magnetization. For each field or observation point, the 3D solution involves 24 nondimensional quantities, arising from the eight vertex positions of the magnet and the three components of the magnetic field. The only unknown in the model is the value of magnetization, with all other model quantities defined in terms of field position and magnet location. The longitudinal magnetic field component in the direction of magnetization is bounded everywhere, but discontinuous across the magnet faces parallel to the magnetization direction. The transverse magnetic fields are logarithmically unbounded on approaching a vertex of the magnet.   doi:10.1017/S1446181120000097

scholarly journals Expansion of the high field-boosted superconductivity in UTe2 under pressure

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Sheng Ran ◽  
Shanta R. Saha ◽  
I-Lin Liu ◽  
David Graf ◽  
Johnpierre Paglione ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Field ◽  
Superconducting Phase ◽  
High Symmetry ◽  
First Order ◽  
Superconducting Phases ◽  
Quantum Phenomenon ◽  
Zero Resistance ◽  
Spin Triplet ◽  
The Magnetic Field

AbstractMagnetic field-induced superconductivity is a fascinating quantum phenomenon, whose origin is yet to be fully understood. The recently discovered spin-triplet superconductor, UTe2, exhibits two such superconducting phases, with the second one reentering in the magnetic field of 45 T and persisting up to 65 T. More surprisingly, in order to induce this superconducting phase, the magnetic field has to be applied in a special angle range, not along any high symmetry crystalline direction. Here we investigated the evolution of this high-field-induced superconducting phase under pressure. Two superconducting phases merge together under pressure, and the zero resistance persists up to 45 T, the field limit of the current study. We also reveal that the high-field-induced superconducting phase is completely decoupled from the first-order field-polarized phase transition, different from the previously known example of field-induced superconductivity in URhGe, indicating superconductivity boosted by a different paring mechanism.

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