Prospecting for lunar Helium-3 with a radio-frequency atomic magnetometer

Mining $^3{\rm He}$ from lunar regolith has attracted significant interest in recent years due to the scarcity of $^3{\rm He}$ on Earth and its diverse applications, from cryogenics and medical imaging, to nuclear physics and future nuclear fusion. Given the stringent technical and economic challenges of mining lunar $^3{\rm He}$, precise prospecting is essential. Here we propose a prospecting methodology based on a radio-frequency atomic magnetometer, which can detect the dipolar magnetic field of thermally polarized $^3{\rm He}$ spins. With a 200 g regolith sample and an rf-magnetometer with sensitivity $1~{\rm fT/\sqrt{Hz}}$ we can detect $^3{\rm He}$ with abundance 5 ppb within a measurement time of just 5 min. The associated apparatus is lightweight and significantly more cost-effective than alternative measurement techniques. The proposed prospecting method is readily deployable and could substantially improve the technical and economic feasibility of mining lunar $^3{\rm He}$.