SQUIDS as detectors in a new experiment to measure the neutron electric dipole moment

A new experiment has been proposed at Los Alamos National Laboratory to mea sure the neutron electric dipole moment (EDM) to 4x10(-28) ecm, a factor of 250 times better than the current experimental limit. Such a measure of th e neutron EDM would challenge the theories of supersymmetry and time revers al violation as the origin of the observed cosmological asymmetry in the ra tio of baryons to antibaryons. One possible design for this new experiment includes the use of low temperature superconducting (LTS) SQUIDs coupled to large (similar to 100 cm(2)) pick-up coils to measure the precession frequ ency of the spin-polarized He-3 atoms that act as polarizer, spin analyzer, and detector for the ultra-cold neutrons used in the experiment. The metho d of directly measuring the 3He precession signal eliminates the need for v ery uniform magnetic fields (a major source of systematic error in these ty pes of experiments). It is estimated that a nux of similar to 2x10(-16) Tm- 2 (0.1 Phi(0)) will be coupled into the pick-up coils. To achieve the requi red signal-to-noise ratio one must have a flux resolution of d Phi(SQ)=5x10 (-6) Phi(0)/Hz at 10 Hz. While this is close to the sensitivity available i n commercial devices, the effects of coupling to such a large pick-up coil and nus noise from other sources in the experiment still need to be underst ood. To determine the feasibility of using SQUIDs in such an application we designed and built a superconducting test cell, which simulates major feat ures of the proposed EDM experiment, and we developed a two-SQUID readout s ystem that will reduce SQUID noise in the experiment. We present an overvie w of the EDM experiment with SQUIDs, estimations of required SQUID paramete rs and experimental considerations. We also present the measured performanc e of a single magnetometer in the test cell as well as the performance of t he two SQUID readout technique.