FLUX CREEP IN HARD SUPERCONDUCTORS

Journal Article · Sun Sep 15 04:00:00 EDT 1963 · Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D

DOI:https://doi.org/10.1103/PhysRev.131.2486· OSTI ID:4633688

Kim, Y B; Hempstead, C F; Strnad, A R

Resistive states of hard superconductors are investigated by tube magnetization and resistance measurements. The flux-creep theory of Anderson is very effective in accounting for the experimental observations reported herein. Resistive phenomena were observed in the presence of transport current density J and magnetic field B perpendicular to J. It is found that the whole spectrum of resistive states can be represented in terms of a single parameter alpha == J(B + B/sub o/, where B/sub o/ is a constant of the material. This parameter represents essentially the Lorentz force or the magnetic pressure gradient in the material. While a wide range of alpha values is possible, under given experimental conditions superconductivity usually cannot be maintained above a critical value. In tube magnetization, the critical value alpha /sub c/ is determined primarily by the rate with which the persistent current J decays. If alpha is raised beyond alpha c, J decays rapidly and alpha quickly falls near to alpha /sub c/. alpha continues to decrease slowly, but proportional to the logarithm of time as predicted by the theory. The observed temperature dependence of alpha /sub c/ is accounted for by the theory. Discrete, stochastic charges in field anticipated from the motion of flux bundles were detected through picknp coils placed in close proximity to the superconducting tube. In resistance measurements, voltages appearing across 3Nb-Zr wire samples were measured by supplying J externally in the presence of a perpendicular field H. The voltage observed is interpreted as a manifestation of an uncompensated emf arising from flux creep. At a given temperature, voltage readings obtained over a wide range of J and H are found to be a function of alpha = J(H + B/sub o/) only. V( alpha ,T) follows qualitatively a form expected from the theory. In resistance measurements, the critical value alpha /sup p/ is determined by the power dissipation in the material. If alpha is raised beyond alpha /sup p/, thermal conduction lags the power dissipation and the sample undergoes a catastrophic transition to the normal state. (auth)

• Research Organization: Bell Telephone Labs., Murray Hills, N.J.
• NSA Number: NSA-17-036489
• OSTI ID: 4633688
• Journal Information: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D, Journal Name: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D Vol. Vol: 131; ISSN PHRVA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

COILS
CURRENTS
ELECTRIC CONDUCTIVITY
ELECTRIC POTENTIAL
EQUATIONS
MAGNETIC FIELDS
MEASURED VALUES
MOTION
NIOBIUM ALLOYS
PHYSICS
PRESSURE
SUPERCONDUCTIVITY
SUSCEPTIBILITY
TEMPERATURE
THERMAL CONDUCTIVITY
TUBES
VARIATIONS
WIRES
ZIRCONIUM ALLOYS