Dressed Helium Comagnetometry for the Neutron EDM Experiment

The electric dipole moment (EDM) of the neutron provides a unique window into CP-violating processes in the light-quark baryon sector. A new experiment with ultracold neutrons aims to measure the neutron EDM with a sensitivity of $10^{-27}$~e-cm. The experiment will use a novel direct comagnetometry technique with polarized $^{3}$He ``dressed'' by a RF magnetic field, to match its effective magnetic moment to that of the neutron. This method allows a sensitive measurement of the neutron precession rate relative to the $^{3}$He. We have studied the dressed $^{3}$He spin system experimentally using a polarized $^{3}$He source at Los~Alamos. Results of this first measurement of spin dressing effects on the $^{3}$He magnetic moment will be presented.