Polarized Ultracold Neutrons and Spin Analysis in the LANL nEDM Experiment

The neutron Electric Dipole Moment (nEDM) experiment at the Los Alamos National Laboratory aims to achieve an improved level of precision of the neutron dipole moment. Our experiment would yield a sensitivity of |dn|~ 3x10-27 e-cm, 10 times better than the current upper limit of |dn| ~ 3x10-26 e-cm. To reach these values, the experiment requires polarized ultracold neutrons (UCN) to be transported into a magnetically shielded room (MSR), in which a highly uniform B0 field (1~micro T) is applied to perform Nuclear Magnetic Resonance (NMR) measurements. The spin state of the neutrons entering the MSR is prepared by a 6~T superconducting magnet, and the final spin states (after NMR) are analyzed using a simultaneous spin analyzer system. The spin analyzer determines the spin state of neutrons by transmitting through an iron foil, fully magnetized by NdBFe irons, and a RF field to flip the spin states; the transmitted neutrons are captured in a 10B coated ZnS scintillator and counted by PhotoMultiplier Tubes (PMT). In my talk, I will discuss the methods used to improve the nEDM sensitivity limit in our experiment and report the progress on the construction, focusing on the implementation of the spin analyzer.

The author thanks and acknowledges the support of Indiana University, the Los Alamos National Laboratory, and National Science Foundation, grant PHY-1828512.