Optimization of metastability-exchange optical pumping of 3 He for low-field magnetometry

Le résumé fourni par la source

Abstract Spin-polarized 3 He serves as an excellent probe for absolute magnetometry across a wide dynamic range. We report the polarization optimization of 3 He via metastability-exchange optical pumping (MEOP) in low fields. The effects of pump laser power, laser circular polarization, and discharge strength on nuclear polarization are examined. A maximum polarization of ∼69% is achieved in both pure 3 He and 3 He– 4 He cells, with the latter showing faster buildup. Additionally, we examine the transverse relaxation time T 2 at various holding magnetic field strengths and observe suppression of discharge-induced decoherence at low fields. The relaxation time is further extended when pumping is turned off, reaching a maximum T 2 of 145 s in the low-field regime. Under optimal conditions, an expected field sensitivity (Cramér-Rao lower bound) of 88 fT or a noise-equivalent sensitivity of 0.96 pT / H z is achieved at 0.12 μ T , highlighting the potential of MEOP-based 3 He for absolute, cryogen-free magnetometry.

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