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 172 Yb + and 115 In + ions for an optical clock based on the 1 S 0 - 3 P 0 transition in 115 In + . We successfully have trapped and laser-cooled Coulomb crystals of 172 Yb + ions in our new scalable ion trap that are used to characterize the trap and to sympathetically cool 115 In + 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.