Magnetic fields and monitoring for the Los Alamos neutron EDM experiment

The Los Alamos neutron electric dipole moment (nEDM) experiment plans to improve nEDM sensitivity to 2x10^-27 e-cm, a factor of 10 beyond the current upper limit, using the Los Alamos ultracold neutron (UCN) source. The P-and-T (or CP) violating coupling of an electric field to the neutron spin will be measured using a time-separated oscillatory field Ramsey sequence in two UCN storage chambers with opposite electric fields and mercury comagnetometry. The experiment relies crucially on measurement and control of magnetic fields and gradients that affect the frequency stability, Ramsey sequence, and false-EDM signals arising from the coupling of magnetic field gradients to neutron and mercury motion. This talk will report on the principles and performance of the magnetic field systems for this effort.