A high-precision system for direct current reproduction based on atomic magnetic resonance in helium-4

Abstract

At the D. I. Mendeleyev Institute for Metrology (VNIIM) a high-precision system using helium-4 atomic magnetic resonance has been realized for the automatic reproduction and maintenance of direct current in the range 0.1 A to 1.0 A. A random standard uncertainty of 2 × 10-8 was obtained for stabilization at 1 A, with a non-linearity of less than 2 × 10-7 in the frequency-to-current conversion factor. The conversion factor was determined experimentally through the gyromagnetic ratio of helium-4 atoms and the calculable coil constant of a high-precision solenoid. The technique was used to determine the gyromagnetic ratio of the proton and for the accurate reproduction of the tesla using the calculable solenoid.