Feasibility study of a He-3-magnetometer for neutron electric dipole moment experiments

We report on a He-3-magnetometer capable of detecting tiny magnetic field f luctuations of less than 10(-14) T in experiments for measuring the electri c dipole moment (EDM) of the neutron. It is based on the Ramsey technique o f separated oscillating fields and uses nuclear spin-polarized He-3 gas whi ch is stored in two vessels of V similar or equal to 10 1 in a sandwich-typ e arrangement around the storage bottle for ultra-cold neutrons (UCN). The gas is polarized by means of optical pumping in a separate, small discharge cell at pressures around 0.5 mbar and is then expanded into the actual mag netometer volume. To detect the polarization of He-3 gas at the end of the storage cycle the gas is pumped out by means of an oil-diffusion pump and c ompressed again into the discharge cell where optical detection of nuclear polarization is used. (C) 2000 Elsevier Science B.V. All rights reserved.