MEASUREMENT OF MAGNETIC FIELD GRADIENTS BY THE HALL EFFECT

A magnetic field gradient measuring device which uses the Hall effect in germanium has been constructed. The field sensitive element was a bar of germanium 1 mm by 1 mm by 12 mm with two sets of Hall leads each attached 2 mm from the center of the bar. With 100 cps current flowing in the long direction of the bar, the two Hall voltages were subtracted to give an output directly proportional to the magnetic field gradient. The instrument was tested in a calculable magnetic field produced by step pole pieces, and gradients from 5 gauss/inch to 500 gauss/inch in magnetic fields below 5000 gauss were measured. The instrument will also measure magnetic field strengths and relative gradients. The usefulness of the instrument is still uncertain because of errors caused by excessive field dependence of the gradient voltage. (auth)