Experimental confirmation of micromotion shift cancellation via operation at trap magic frequency and reduction in evaluated systematic uncertainties for the 88Sr+ optical frequency standard at 445 THz

We describe recent experiments and results which show the effective cancellation of micromotion induced systematic shifts for the 445-THz reference transition in a trapped and laser cooled ⁸⁸Sr⁺ single ion reference. Using two different ion trap systems based on a Paul and endcap design, the critical or magic frequency at which micromotion effects cancel has been effectively measured at 14.4 MHz. This work also allows an improved determination of the polarizability difference of the ground and excited states and an improvement in the evaluated blackbody shifts to the low 10^-17 level.