Direct temperature determination of a sympathetically cooled large 113Cd+ ion crystal for a microwave clock

This paper reports direct temperature determination of sympathetically cooled Cd-113(+) ions with laser-pcooled Mg-24(+) in a linear Paul trap. The sympathetically cooled ion species distribute in the outer shell of the large ensembles, which contain up to 3.3 x 10(5) ions. With optimized parameters, the minimum temperature of the sympathetically cooled Cd-113(+) ions was measured to be on the order of 10 mK. These results are promising for the performance of microwave atomic clocks. The second-porder Doppler frequency shift is two orders of magnitude lower (from 1.88 x 10(-14) to 6.26 x 10(-16)) and the Dick effect is suppressed. Published under license by AIP Publishing.