On excessive resistance and heat generation of aluminum conductor due to magnetic field inhomogeneity

Abstract

Inhomogeneity of current distribution of high purity aluminum at 4.2 and 30 К is studied. One of major problem of cryogenic devices generating high magnetic field is an enhancement of magnetoresistance and respective heat generation due to inhomogeneity of composite conductor in the place of its interface and due to inhomogeneity of magnetic field through device's coils because inner and outer coils are at different magnitudes of magnetic field. Usually an include of magnetic field inhomogeneity into resistance increase is neglected. A paper proposed here is to show that at cryogenic temperatures the amount of excessive resistance connected with magnetic field in homogeneity may be comparable in magnitude with traditional enhancement of resistance due to interface of composite conductors. The testing is done by measurement of potential distribution over conductors оf 99.999% Al being under inhomogeneous magnetic field action at 4.2 K. The magnetic field gradient of 0.1 cm-1 is directed along current flow. On the other hand a calculation of nonuniform current distribution and enhancement of resistance due to decrease of effective conductor cross section is made on the base of experimental boundary conditions for electric potential. A correlation of experimental data with calculation is made and discussed for different low temperature range and purity of metal in quasi free electron approximation. Research is supported by Fund of Fundamental Investigations of the Republic of Belarus.