Level assessment of ⁸⁷Rb in rubidium-filled MEMS vapor cells by X-ray imaging for atomic magnetometers

Quantitative assessments of the level and lifetime of alkali metal in the atomic vapor cells are essential for improving the stability of atomic magnetometers. In this paper, a fast and non-destructive approach is proposed to directly characterize the level of 87 Rb in a hermetic MEMS vapor cell. The MEMS-compatible 87 Rb evaporation technique is developed to dispense 87 Rb in the vapor cells with high efficiency. The morphology of the metallic 87 Rb in the MEMS vapor cell is visualized by the non-destructive X-ray technique, and the measured contact angle is 43° ± 2°. Combined with the image recognition, the quantitative characterization of the 87 Rb is achieved, and the consumption rates of 87 Rb in MEMS cells are experimentally investigated. The presented approach is beneficial for the fabrication and performance enhancement of vapor cells for atomic magnetometers.