Internal Temperature Reconstruction of Alkali Metal Gas Cells Based on the ART Algorithm

The spin-exchange relaxation-free (SERF) atomic magnetometer is an ultra-high-sensitivity magnetic field measurement device with extensive applications in biomedicine, space exploration, and fundamental scientific research. SERF magnetometers rely on saturated vapor of polarized alkali metal atoms within a gas cell for operation. Since the temperature inside the gas cell directly affects the polarizability and saturation level of the vapor, accurately measuring the gas cell temperature is a critical challenge in SERF magnetometer research. Since the gas chamber is a sealed glass cavity, traditional contact-based temperature measurement cannot access the internal temperature. Laser temperature measurement is limited by absorption saturation at resonance points, leading to reduced accuracy. Based on the theory of internal spatial temperature distribution measurement, this study incorporates an infrared thermal imager into the temperature measurement apparatus to capture thermal radiation images of the alkali metal gas cell during operation. After eliminating external radiation interference, an algebraic reconstruction technique (ART) is employed to reconstruct the spatial temperature distribution within the gas cell. Concurrently, atomic absorption spectroscopy is used to measure the temperature distribution near the central cross-section of the gas cell. Experimental results demonstrate that the algorithm-reconstructed data aligns with the internal temperature variation trends of the cell, with a minimum difference of 1.33 K. This confirms the high accuracy of the reconstruction results, effectively addressing the challenge of measuring temperatures within the cell.