A Room-Temperature Operational Alignment Magnetometer Utilizing Free-Spin Precession

An alignment magnetometer based on free-spin precession (FSP) has been deployed in the geomagnetic range. A linearly polarized probe beam is utilized to create alignment in a buffer-gas-free paraffin-coated natural abundance rubidium vapor cell at room temperature exposed to a pulsed radio frequency field. Furthermore, the utilization of hyperfine-selective optical repumping employing linearly polarized beams amplifies the proportion of responsive atoms. As a consequence, this leads to a remarkable enhancement in the optical rotation signal. This paper reports measurements with a minor static magnetic field of about 1 mu T$\umu {\text{T}}$ inside a four-layer mu$\umu$-metal shield, achieving a system noise level of 0.16 pT(Hz${\text{pT\nobreakspace }}(\sqrt {{\text{Hz}}}$)-1. With a static magnetic field amplitude of 48.5 mu T$\umu {\text{T}}$ (in proximity to Earth's magnetic field), the noise level is approximate to 0.75 pT(Hz${\text{pT }}(\sqrt {{\text{Hz}}}$)-1. This manuscript introduces a breakthrough alignment magnetometry using a buffer-gas-free paraffin-coated rubidium cell. The concept of leveraging free-spin precession within geomagnetic ranges is presented, maintaining room temperature operation. This innovation paves the way for operating at room temperature within the geomagnetic range while maintaining an ultrahigh level of sensitivity.image