LASER COOLED, STORED ION EXPERIMENTS AT NBS AND POSSIBLE APPLICATIONS TO MICROWAVE AND OPTICAL FREQUENCY STANDARDS

Abstract

Research on stored ion frequency standards at the United States National Bureau of Standards is brief 1 y discussed. We summarize past work and indicate directions of future research. Introduction. - The purpose of this paper is to briefly summarize the work at the National Bureau of Standards (NBS) which has been directed towards realizing a frequency standard based on stored ions. The similar work of other groups (I) is not discussed here. This summary briefly describes past work and indicates future directions of research at NBS. The stored ion work at NBS was initiated in the Fall of 1977. The goal of this work has been to devise a technique for realizing a frequency standard whose accuracy would be significantly better than that of the Cs atomic beam frequency standard. With this in mind, the ion storage method (2) was pursued because it can provide long confinement times without the usual perturbations associated with confinement (e.g., the wall shift in the H-maser). The initial work was directed toward realizing laser c ooling of ions 131, since this would provide a way to substantially suppress the frequency shift due to the second-order Doppler or time-di lation effect. For these initial experi- ments, Mg+ ions were stored in a Penning trap. Mg+ ions were chosen, since the electronic s tructure is fairly simple (i.e., like that of neutral alkali atoms) and required a laser source at 280 nm. The Penning trap was chosen because the residual h eating mechanisms (at least for a cloud of ions) are l ess than for the