The Study Of Ramsey And Rabi Frequency Pulling Shift In Cesium Fountain Clock

As primary frequency, Cesium atomic fountain consists of two most important property indexes, which are frequency stability and frequency accuracy. Its frequency accuracy is summarized by evaluating 13 frequency shifts separately, which includes Ramsey and Rabi frequency pulling shift.Because of complex and little frequency shift, we need many novel computing methods and experimental techniques.The thesis studies the Ramsey and Rabi frequency pulling shift based on the under-developed NTSC-F1. The paper is as follows:(1) By calculating the atomic transition probabilities in Ramsey configuration,we derived Ramsey and Rabi frequency pulling shift formula. Unlike PTB’s density matrix method by Neumann evolution equation, we solved the time evolution operator numerically, then let the time evolution operator act on the initial atomic state to obtain Ramsey and Rabi frequency pulling shift. This method can not only saves computing time and facilitates to get atomic Ramsey and Rabi frequency pulling shift due to different initial atomic state.(2)In Cesium fountain, the theory shows that the magnitude of Ramsey and Rabi frequency pulling shift without coherence reduces from 10-15 with coherence to 10-18, when the Ramsey cavity’s microwave pulse area is π/2.(3)By means of feeding two microwaves to selection cavity, we prepared the initial atomic coherence with the population difference of 4.22%, and we obtained the atomic Ramsey fringes. At last, we measured Ramsey and Rabi frequency pulling shift by changing the extra coil current which was set between the two cavities, the diagram shows the trigonometric function between Ramsey and Rabi frequency pulling shift and the magnetic, which verified the theoretical model.(4)We evaluated Ramsey and Rabi and frequency pulling shift when the Cesium atomic fountain clock in normal operation(the Ramsey cavity’s microwave pulse area is π/2),the initial atomic incoherence with population imbalance 0.07% leads the Ramsey and Rabi and frequency pulling shift is less than 2.6×10-18.