Our magnetometers are based on atomic physics:
- a thermal ensemble of helium-4 atoms is continuously excited by a high-frequency discharge in order to populate the 23S1 metastable state which is a spin-one state, sensitive to the magnetic field
- the metastable ensemble is prepared in a state with a magnetic moment by optical pumping towards 23P levels with a laser at 1083.2 nm
- two radio-frequency fields at different frequencies (9 and 40 kHz) allow exciting parametric resonances. These resonances yield a direct measurement of the 3 components of the magnetic field on the photodetector, in three spectrally separated ranges with a bandwidth of >2 kHz each
