nEDM@SNS Systematics Studies/ Operational test-bed Apparatus at PULSTAR

The neutron electric dipole moment (nEDM) experiment at the Spallation Neutron Source will probe the existence of a nEDM down to $\sim 5 \times 10^{-28}$ e$\cdot$cm. The technique uses a $<0.5$K liquid-$^4$He-filled cryogenic environment containing both polarized $^3$He and trapped ultracold neutrons (UCN). Due to the technical and operational challenges in the experiment, a smaller-scale apparatus is needed to minimize both risk and commissioning/operational time. The design mirrors that of the larger-scale apparatus, but without an electric field and a turn-around time of order a week as compared to several months. Using the small-scale device, we will develop operational techniques for UCN -$^3$He spin manipulations and quantify the systematic effect related to magnetic field gradients. The apparatus will use neutrons from the NC State UCN source and polarized $^3$He from a MEOP system. At present we have completed commissioning of the new non-magnetic dewar and are assembling and testing cryogenic essentials of the apparatus