Accession Number : AD0803395

Title :   PHENOMENON OF SUPERCONDUCTIVITY (PHASE II).

Descriptive Note : Progress rept. 16 Mar-15 Sep 66,

Corporate Author : RCA LABS PRINCETON NJ

Personal Author(s) : Gittleman, Jonathan I. ; Cody, George D. ; Cullen, Glenn W. ; Enstrom, Ronald E. ; Halloran, John J.

Report Date : OCT 1966

Pagination or Media Count : 113

Abstract : Magnetization studies of single-crystal Nb3Sn have provided the first unambiguous determination of the Ginzburg-Landau parameter k(T sub c) and (dH sub c/dT) sub T sub c. These are k(T sub c) = 22 + or - 3 and (dH sub c/dT) sub T sub c = -640 G/degree K + or - 10%. Magnetization measurements of very pure Nb and Nb-Ta alloys are reported. A small amount of hysteresis observed in the magnetization curves is temperature-dependent and has a minimum near T = 0.9 T sub c. This is explained in terms of the Kim-Anderson theory. Also, determinations of k(T sub c) indicate an intrinsic k which is higher in the alloys than in either pure Nb or pure Ta. Specific heat measurements of Nb3Sn in the normal state have been made down to 15 K using a 55-kG Nb3Sn solenoid. Although the entropy anomaly can be removed by considering a strong coupling electron-phonon interaction, 15 K is not a sufficiently low temperature to permit the justification of the use of such a term. Nor does it account for the anomaly in the superconducting specific heat. Nb4Sn, unlike Nb3Sn, is remarkably well behaved both with respect to its normal state heat as well as the agreement of its superconducting heat with the BCS theory. Electron microscopy has been used to observe the effects of neutron radiation damage on single-crystal Nb3Sn. Chemical thinning procedures are described which, for the first time, permit the use of the electron microscope for this purpose. A neutron-irradiated specimen examined with the electron microscope exhibited spots similar to that observed in copper.

Descriptors :   (*SUPERCONDUCTIVITY, THEORY), (*NIOBIUM ALLOYS, MAGNETIC PROPERTIES), SINGLE CRYSTALS, TIN ALLOYS, TANTALUM ALLOYS, SPECIFIC HEAT, VOLTAGE, NEUTRONS, RADIATION EFFECTS, MEASUREMENT, CRYSTAL SUBSTRUCTURE.

Subject Categories : Electricity and Magnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE