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Author Zar, J. L.
Sponsorship USDOE
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword PHYSICS ♦ COLD WORKING ♦ CONFIGURATION ♦ CURRENTS ♦ EDDY CURRENTS ♦ ELECTRIC CONDUCTIVITY ♦ EQUATIONS ♦ FREQUENCY ♦ INDUCTION ♦ LOW TEMPERATURE ♦ MAGNETIC FIELDS ♦ MAGNETISM ♦ MEASURED VALUES ♦ MOLYBDENUM ALLOYS ♦ NIOBIUM ALLOYS ♦ RHENIUM ALLOYS ♦ SUPERCONDUCTIVITY ♦ THICKNESS ♦ WIRES ♦ ZIRCONIUM ALLOYS
Abstract A direct electrical measuremert is made of the resistance of nonideal superconductors at power and audio frequencies, at 4.2 deg K, and in zero applied field. The resistance of short saraples of several Nb-- Zr and Mo--Re alloys is found to be independert of the composition and of impressed current. The resistivity is found to depend on f/sup 0.5/ above 1000 cps and on f/sup 1.7/ for frequencies f below 500 cps. The resistance is also independent of wire diameter for some sizes near 0.25 mm. Three explanations are considered to account for resistance at low frequencies. Relaxation time effects are ruled out by the observed frequency dependence at high frequencies. Inductive coupling between the magnetic fields of the normal and the superconducting currents leads to a resistance effect six orders of magnitude lower than the observed ones, and an f/ sup 2.0/ dependence. Trapping of flux within the superconductor leads to an upper bound for the resistance that agrees with the experimental results in being independent of the wire diameter and the current, and giving the approximately correct resistance values, although an f/sup 1.0/ dependence. The measurements suggest that the a-c resistance may result from eddy currents induced in normal regions near the surface of heavily cold-worked superconductors. (auth)
ISSN 00218979
Educational Use Research
Learning Resource Type Article
Publisher Date 1964-05-01
Publisher Department Avco Corp., Everett, Mass.
Journal Journal of Applied Physics
Volume Number 35
Organization Avco Corp., Everett, Mass.


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