Minimizing time-dilation in ion traps — Towards an optical clock with Coulomb crystals

We present the status of our new experiment to lasercool linear chains of ¹⁷²Yb⁺ and ¹¹⁵In⁺ ions for an optical clock based on the ¹S₀-³P₀ transition in ¹¹⁵In⁺. We successfully have trapped and laser-cooled Coulomb crystals of ¹⁷²Yb⁺ ions in our new scalable ion trap that are used to characterize the trap and to sympathetically cool ¹¹⁵In⁺ ions. We could demonstrate an area of more than 65 μm, where the fractional frequency shifts due to time dilation are below 10^-18 for both ions.