Progress Towards a Cadimium Ion Microwave Clock Based on Sympathetic Cooling

The precision of Cadmium ion microwave clock based on linear quadrupole trap is mainly determined by the measurement accuracy of hyperfine splitting of the ground state of
¹¹³
Cd
⁺
. To reduce the second order Doppler frequency shift(SODFS), which is one of the main frequency shifts, we take advantages of sympathetic cooling by
²⁴
Mg
⁺
ions to keep the Cadmium ion clouds at relatively low temperature during the interrogation of clock transition. By comparing the experiment results with molecular-dynamics(MD) simulation, we discuss the efficiency of sympathetic cooling and its influence on our clock's performance.