Calibration of SQUID Magnetometers with Metastability-Exchange Optically Pumped 3He Precession for the 129Xe EDM Experiment

A new measurement of the 129Xe electric dipole moment (EDM) using 3He comagnetometry is under development at Los Alamos National Lab. Spin precession of the noble gases in combined electric and magnetic fields will be detected with a novel SQUID magnetometer system. For development, calibration, and testing of the magnetic field and SQUID systems, we have developed a compact metastability-exchange optimally pumped device to generate a 3He precession signal. A 1083 nm fiber-coupled diode laser polarizes metastable 3He in a discharge, and the nuclear spin is transferred to ground-state atoms through metastability exchange in a glass cell with 2-10 torr of 3He. The 3He spins are "tipped" with a pi/2 pulse and precess at the 3He Larmor frequency in a few-µT magnetic field. The system has been developed and calibrated with optically pumped 85Rbmagnetometers. With coherence times of 30 minutes or more, our device is a robust and versatile tool for magnetometer characterization in 129Xe EDM and future precision magnetic field experiments.