AC-driven temperature measurement of vapor cell in a compact atomic magnetometer with suppressed thermometry-induced magnetic interference

Stable temperature control is essential for maintaining the atomic vapor density in spin-exchange relaxation free (SERF) magnetometers. Although contact-based resistance temperature detector (RTD) offers a standalone temperature monitor of a vapor cell, the magnetic interference generated by traditional DC-driven RTD perturbs atomic polarization and degrades the sensitivity of the SERF magnetometer. This article provides a new solution to the conflict between continuous, stable, high-precision thermometry and magnetic silence in compact SERF magnetometers. First, we provide an order-of-magnitude estimate of how DC-driven RTD currents contribute to additional gradient-induced relaxation (R_grad). To this end, an AC-driven RTD method is proposed that exploits dynamical decoupling to average the gradient fields experienced by the atomic spins to zero. In addition, the methodology for implementing suppressed magnetic-interference thermometry using an AC bridge and lock-in demodulation on a custom-made circuit is demonstrated, enabling continuous, high-precision temperature stabilization. The proposed AC-driven thermometry was experimentally validated on multiple magnetometers, demonstrating improved sensitivity relative to DC-driven thermometry while maintaining stable temperature control. This work provides valuable references for improving the sensitivity of SERF magnetometers and offers a new solution to suppress crosstalk from temperature sensors.