A new concept is proposed to measure a dc magnetic induction vector B whose magnitude is sufficiently large to saturate a small ferro- or ferrimagnetic sphere and align its magnetization vector M paralle to B. The direction of M is measured by modulating B locally at a convenient ac frequency by one or more small exciter coils near the sphere and using separate detector coils to measure components of the modulated induction due to the ac perturbed orientation of M. Equations are derived to relate the perturbed quantities to the original induction B. Several combinations of exciter and detector coils are possible, especially if distinct frequencies are used for each direction component. All three vector components of B can be calculated from the raw data. Because the proposed sensor has neither moving parts nor semiconductor components, it should be suitable for measurements in ionizing radiation environments, such as long pulse or steady state magnetically confined fusion power reactors.
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