Improved compensation and measurement of the magnetic gradients in an atomic vapor cell

Magnetic field gradients reduce the transverse relaxation time of nuclear spins, which usually degrades the sensitivity of atomic sensors based on nuclear spins. We demonstrate improved magnetic field gradient compensation by applying first-order and second-order magnetic gradients simultaneously in a cubic vapor cell containing Rb-87 vapor and Xe-129 gas. Compared with applying only first-order magnetic gradient compensation, the transverse relaxation time of Xe-129 is up to 4.3 times longer when applying both first-order and second-order compensating magnetic gradients, which indicates that the total magnetic gradient is greatly suppressed by the joint compensation in our experiment. The magnetic gradients induced by the polarized Rb-87 spins, the static magnetic field, and the residual magnetic field are also explored. As the main sources of internal magnetic inhomogeneities, these gradients are experimentally validated to have a sizable value. Furthermore, the total internal magnetic gradient in the system could be self-compensated when the directions of these internal gradient components are appropriately set. The experimental results in this paper are important for suppressing the magnetic gradients and optimizing the gradient compensation in nuclear magnetic resonance systems.