Abstract:

A K-3 He co-magnetometer has been developed for a test of Lorentz and CPT symmetry. Polarized K vapor forms a spin-exchange relaxation-free (SERF) magnetometer that has record sensitivity of about 1 fT/[Special characters omitted.] . The polarized 3 He effectively suppresses sensitivity to the magnetic fields and gradients. Together, the K-3 He co-magnetometer retains sensitivity to anomalous, CPT- and Lorentz-violating fields that couple to electron and nuclear spins differently than a normal magnetic field. Data over the course of 15 months provide upper limits on the coupling energy of a CPT-violating field to neutron spin, b n < 1.4 ? 10-31 GeV, to proton spin, b p < 4.4 ? 10-30 GeV, and to electron spin, b e < 1.0 ? 10-28 GeV. These limits are consistent with the existing limits of b n < 1.1 ? 10-31 GeV (Bear et al., 2002) and b e < 3.0 ? 10-29 GeV (Heckel et al., 2000). The proton sensitivity is better than the published limit of b p < 1.8 ? 10-27 GeV (Phillips et al., 2001). The long-term sensitivity of the co-magnetometer was significantly limited by sources of systematic noise.

The co-magnetometer provides a robust platform for precision measurements primarily due to its inherent insensitivity to magnetic field drift and field gradients. Detailed analytic and numerical modeling of the coupled spin ensemble dynamics provides good agreement with steady state and transient response measurements. Elaborate procedures have been developed for running the system optimally and minimizing the magnetic fields and lightshifts in the system.

The co-magnetometer also forms a sensitive gyroscope that inherits all the magnetic insensitivity features of the co-magnetometer and adds insensitivity to magnetic fields fast transients. The sensitivity of this gyroscope is competitive with existing compact gyroscope techniques.