Ultra low noise induction magnetometer for variable temperature operation

In recent publications, the authors have reported on the performance of com pact broadband induction magnetometer systems with an operating bandwidth f rom 100 mu Hz to 1 MHz. The best room temperature noise performance achieve d was similar to 500 fT/root Hz from 10 kHz to 1 MHz. In this paper, we des cribe improvements to the coil design and signal processing electronics, wh ich result in a further reduction of the noise (similar to 50 fT/root Hz, i n 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 r eduction in noise may be achieved by operating the system at a reduced temp erature (77 K). (C) 2000 Elsevier Science S.A. All rights reserved.