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

Abstract

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. It should be mentioned that there is an inhomogeneity of magnetic field through device’s coils because the inner and outer coils are at different magnitudes of magnetic field. Usually a contribution 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 inhomogeneity may be comparable in magnitude with traditional enhancement of resistance due to interlace of composite conductors. The testing is done by measurement of potential distribution over aluminum conductors being under inhomogeneous magnetic field action at 4.2 K. fhe magnetic field gradient up to 35 kOe/cm is directed along current flow. A calculation of nonuniform current distribution and enhancement of resistance due to decrease of effective conductor cross section is made. A correlation of experimental data with calculation is established and discussed.