The $^{3}$He injection test for the search of neutron electric dipole moment (nEDM)

The proposed nEDM experiment at the Spallation Neutron Source (ORNL) aims at a sensitivity of 10$^{-28}$ e-cm. The experimental strategy is to form a three-component fluid of ultracold neutrons and $^{3}$He atoms in a bath of superfluid $^ {4}$He. Polarized $^{3}$He serves as a co-magnetometer and an ultracold neutron spin precessing frequency analyzer, using the spin-dependent nuclear reaction: $\vec{n}+\vec{^{3}He} \rightarrow p + t + 764$ keV. The injection test described in this talk is to study methods of injecting polarized $^{3}$He from an Atomic Beam Source (ABS) into the superfluid $^{4}$He and demonstrate that the polarization loss is acceptable for the nEDM experiment. In this presentation, I describe the design of the magnet system, a pulsed NMR system for polarization measurement, and cryogenic issues associated with the injection test apparatus.