Study of the physics package for high performance rubidium frequency standards

Abstract

Frequency stability of an atomic frequency standard depends mainly on the Signal to Noise Ratio (SNR) of atomic discrimination signal. For a Rubidium Atomic Frequency Standard (RAFS), the SNR is closely related to the characteristics of the cavity-cell assembly in physics package. The RAFS in our laboratory is designed based on the slotted tube cavity, and a typical stability of 1.5 × 10 -12 τ -1/2 (1-1000 s) has been achieved. The current cavity used in our design is of a disadvantage of field inhomogeneity. To improve further the stability of the RAFS, a modification of the cavity has been carried out. With this modification, the field homogeneity has been greatly improved, and the cavity size was increased also, enabling to hold a larger absorption cell. According to a theoretical evaluation, the SNR of physics package was enhanced by nearly two times, meeting the need to design a RAFS with a stability better than 1.0 × 10 -12 τ -1/2. © 2012 Springer-Verlag.