A non-thermal method to maintain alkali vapor density of anti-relaxation coating cell in spin exchange relaxation-free magnetometer

The long-term stability of alkali metal vapor cell density is crucial for the performance of Spin Exchange Relaxation-Free (SERF) magnetometers. This paper addresses the issue of atomic density consistency commonly encountered with OTS and paraffin coatings in current quantum magnetometers. For the first time, the LIAD non-thermal method is applied to SERF magnetometers to maintain the long-term stability of alkali metal density. The study identifies the critical roles of desorption light luminous flux and integrating sphere uniformity in enhancing LIAD effectiveness. A new model based on the absorption spectrum of ⁸⁵Rb and ⁸⁷Rb was developed, achieving an R-square value of 0.989 and revealing a rubidium isotopic abundance ratio of 2.8:1, with OTS-coated cells showing the highest density retention. These findings contribute to the advancement of cryogenic SERF magnetometers by providing a deeper understanding of LIAD mechanisms and offering a viable alternative to thermal density control methods.