Ultra low noise induction magnetometer for variable temperature operation

In recent publications, the authors have reported on the performance of compact broadband induction magnetometer systems with an operating bandwidth from 100 mu Hz to 1 MHz. The best room temperature noise performance achieved was similar to 500 fT/root Hz from 10 kHz to 1 MHz. In this paper, we describe improvements to the coil design and signal processing electronics, which result in a further reduction of the noise (similar to 50 fT/root Hz, in the range 1-30 kHz). In addition, we have chosen a magnetic material with a very small temperature dependence allowing us to investigate whether a reduction in noise may be achieved by operating the system at a reduced temperature (77 K). (C) 2000 Elsevier Science S.A. All rights reserved.