The Search for Neutron EDM at TRIUMF

A new ultra cold neutron (UCN) facility is under development with a flagship experiment of measuring the neutron’s electric dipole moment (EDM) with a precision of 10$^{-27}$ e-cm. Construction of the main apparatus is taking place at TRIUMF, with collaborators from Japan and Canada. To measure the nEDM, a magnetic resonance experiment on polarized neutrons is performed, where the uncertainty is limited by how well the magnetic field and its gradient are known. Previous nEDM experiments relied on in-situ measurements of the magnetic field using a Ramsey fringe measurement of the spin precession of $^{199}$Hg (cohabiting with the neutrons). UCN will introduce a dual co-magnetometer with cohabiting $^{129}$Xe and $^{199}$Hg for measuring precise magnetic fields within a neutron storage cell. By simultaneously incorporating two atomic species we can deduce both the magnitude and gradient of the magnetic fields, thereby lowering the systematic uncertainties in the nEDM measurement. $^{129}$Xe was chosen for several reasons including its negligible interaction with the neutrons and $^{199}$Hg. Measuring the magnetic field using polarized $^{129}$Xe involves first spin-selectively exciting a two-photon transition -ground 5p6(1S0) state to the excited 5p$^{5}$($^{2}$P$_{3/2}$)6p state at 252 nm- and then measuring the via fluorescence decay. In my talk I will first present an overview of the Neutron EDM project (both the motivation and the production of UCN at TRIUMF). Following this review, I will discuss my contributing work on the $^{129}$Xe co-magnetometer including the analysis of the two-photon excitation spectrum, and our current progress on the measurements of precession of polarized Xe atoms.