DOUBLE-RESONANCE ATOMIC MAGNETOMETERS - FROM GAS-DISCHARGE TO LASER PUMPING

The ultimate resolving power of the atomic frequency discriminator bas ed on ESR of optically pumped potassium atoms was studied in quest of the best version of the Zeeman Earth-field magnetometer. A perfectly r esolved single line as narrow as 1 Hz was realized at a signal-to-nois e ratio not less than 10(4) within the passband from 0.001 to 1 Hz, pr oviding the ultimate short-term sensitivity better than 10 fT/Hz(1/2). Laser pumping provides similar to 2 times better ultimate short-term resolution and a number of other technical advantages. The main source of systematic errors was found to be light-induced resonance frequenc y shifts, which were studied under laser pumping versus wavelength. Th e base-line stability of the stationary installed magnetometer is expe cted to be of about 10 pT under lamp excitation and can be made much b etter in the case of properly wavelength adjusted laser pumping. Altho ugh expected tilt errors up to 0.1 nT cannot be circumvented by laser pumping, they can be greatly suppressed in the gradiometric mode of ma gnetometers application when Mo or more identical sensors are mounted on a common rigid frame.