Fig. 6
From: Distributed network of optically pumped magnetometers for space weather monitoring
Noise spectral density of the OPM in a bandwidth of 0.1–25 Hz in (a) and Allan Deviation of the OPM running for 12 h in (b). The measurements were performed in a 5-layer mu-metal shield, with a 50 \(\upmu\)T bias field present along the sensitive axis of the magnetometer. The applied field was derived from a set of Helmholtz coils present in the shield, driven with a custom low noise current driver41. The sensor exhibits a sensitivity of \(\approx\) 9 pT/\(\sqrt{\textrm{Hz}}\) at 0.1 Hz and \(\approx\) 3 pT/\(\sqrt{\textrm{Hz}}\) at 1 Hz. The sensitivity of the sensor meets the one-second INTERMAGNET standard40. The sensor achieves the best stability after \(\approx\) 20 s of averaging, after which drift dominates.
