Optimization of the pumping laser beam spatial profile in the MEOP experiment performed at elevated 3He pressures

The efficiency of the metastability exchange optical pumping (MEOP) performed at elevated 3 He gas pressures in high magnetic field was improved by modifying the spatial profile of the pumping laser beam in such a way that it matched the nonuniform distribution of plasma in the optical pumping cell. Comparing to a conventional Gaussian profile, at the 3 He gas pressure equal to 267 mbar, both the achieved nuclear polarization (equal to 26%) and the total magnetization in the cell (equal to 1.37 sccfp) are 60% higher when the annular laser beam profile is applied.