I. Spin-lattice relaxation of dilute solutions of polarized He3 in liquid He4 in low magnetic fields at 4 K. II. An analysis of a proposed cryogenic He3 nuclear gyroscope and its application to a nuclear electric-dipole moment experiment

Measurements were made of the spin-lattice nuclear relaxation time of 0.07% solutions of polarized helium-3 in liquid helium-4 at 4 K by use of an rf-biased SQUID (Superconducting Quantum Interference Device) magnetometer in magnetic fields ranging between 30 microGauss and 3 milliGauss. After the effect of magnetic-gradient-induced relaxation was subtracted by extrapolation to large magnetic fields, it was found that the relaxation time was 40 hours in a 1 cm-diameter Pyrex cell. When the sample cell was prefilled with an amount of hydrogen estimated to be equivalent to uniform wall coating of 30 molecular layers thickness, the extrapolated relaxation time increased to 5 days. It is estimated that this result was dominated by intrinsic relaxation due to helium-3 dipole-dipole interactions in the bulk of the sample. As a potential application, the performance of a proposed cryogenic nuclear gyroscope utilizing a helium-4 - polarized helium-3 gas mixture with SQUID magnetometer readout in zero magnetic field is theoretically analyzed. The possibility of using a modified version of this device based on a polarized helium-3 - superfluid helium-4 mixture for the purpose of an experimental search for an electric-dipole moment in the helium-3 nucleus is also discussed