Precision measurement and suppression of low-frequency noise in a current source with double-resonance alignment magnetometers

Low-noise high-stability current sources have essential applications such as neutron electric dipole moment measurement and high-stability magnetometers. Previous studies mainly focused on frequency noise above 0.1 Hz while less on the low-frequency noise/drift. We use double resonance alignment magnetometers (DRAMs) to measure and suppress the low-frequency noise of a homemade current source (CS) board. The CS board noise level is suppressed by about 10 times in the range of 0.001–0.1 Hz and is reduced to $100\mathrm{nA/}\sqrt{\mathrm{Hz}}$ at 0.001 Hz. The relative stability of CS board can reach 2.2 × 10 ^–8. In addition, the DRAM shows a better resolution and accuracy than a commercial 7.5-digit multimeter when measuring our homemade CS board. Further, by combining the DRAM with a double resonance orientation magnetometer, we may realize a low-noise CS in the 0.001–1000 Hz range.