Supercooling and trapped flux in superconducting molybdenum
Pinatti, Daltro Garcia
Rorschach, Harold E., Jr.
Master of Arts
The supercooling properties of Molybdenum were studied through the use of a Dynamic Method. The KAPPA factor of Ginsburg-Landau was calculated. Using the De Gennes correction this value is 0.22 ± .02. The structure of the phase transition as a function of the rate of sweep of the magnetic field, both for increasing and decreasing field, was studied. An attempt was made to interpret the superconducting-normal transition in terms of the electrodynamic theory of Pippard and Lifshitz. This was not sufficient, and a slow process in the beginning of the transition is necessary. Experimental evidence for this process is presented, and it suggests that surface thermal resistance may be the cause for the slow process. The dynamic method proves to be a potentially useful method for measurements of electrical conductivity. At 751 °K for Molybdenum we measure [see PDF for formula]. The character of the normal-superconducting transition indicates that 2/3 of the cross section of the sample has a sudden flux expulsion. The remaining 1/3 seems to have a gradual expulsion with decreasing field.