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 Rb-87 in a hermetic MEMS vapor cell. The MEMS-compatible Rb-87 evaporation technique is developed to dispense Rb-87 in the vapor cells with high efficiency. The morphology of the metallic Rb-87 in the MEMS vapor cell is visualized by the non-destructive X-ray technique, and the measured contact angle is 43 degrees +/- 2 degrees. Combined with the image recognition, the quantitative characterization of the Rb-87 is achieved, and the consumption rates of Rb-87 in MEMS cells are experimentally investigated. The presented approach is beneficial for the fabrication and performance enhancement of vapor cells for atomic magnetometers. (c) 2024 The Japan Society of Applied Physics