New Classes of Systematic Effects in Gas Spin Comagnetometers

Atomic comagnetometers are widely used in precision measurements searching for spin interactions beyond the standard model. We describe a new ${}^3\mathrm{He}\text{−}{}^{129}\mathrm{Xe}$ comagnetometer probed by Rb atoms and use it to identify two general classes of systematic effects in gas comagnetometers, one associated with diffusion in second-order magnetic-field gradients and another due to temperature gradients. We also develop and confirm experimentally a general and practical approach for calculating spin relaxation and frequency shifts due to arbitrary magnetic-field gradients.

Figure 1

(a) Top view of experimental setup. BE: beam expander, PBS: polarizing beam splitter, PO: polarizer, PD: photodiode, PEM: photoelastic modulator. (b) The sequence of the pulsed operation and an example of the signal recorded during the measurement pulse. (c) The fractional suppression of the Rb backpolarization generated by spin exchange with ${}^{129}\mathrm{Xe}$ as a function of the amplitude and frequency of the depolarizing field.

Figure 2

Measurements of the transverse relaxation rate for ${}^3\mathrm{He}$ and ${}^{129}\mathrm{Xe}$ due to linear (left panel) and quadratic (right panel) magnetic-field gradients (points), together with results of the matrix analysis (lines) with no adjustable parameters.

Figure 3

Changes in the ratio of the spin-precession frequencies $g$ due to the quadratic magnetic-field gradient $\delta B_z^{(2)}$. The three data presented are for the cell centered relative to the gradient coil (squares), displaced in the transverse direction by 1.7 mm (empty circles), and displaced along the $\widehat{z}$ direction by 1.3 mm (triangles). The lines are model predictions with no free parameters.

Figure 4

Changes in the response of the frequency ratio $g$ to a linear magnetic-field gradient $\partial B_z/\partial y$ in the presence of temperature gradient $\partial T/\partial y$ across the cell. $\mathrm{\Delta }T$ denotes the temperature difference between the top and bottom of the cell.