A transportable optical lattice clock

We present the experimental setup and first results of PTB's transportable ⁸⁷Sr clock. It consists of a physics package, several compact laser breadboards, and a transportable high finesse cavity for the clock laser. A comparison of the transportable system with our stationary optical lattice clock yields an instability of 2.2 x 10^-15 √s/τ for the transportable clock. The current fractional uncertainty of 1 × 10^-15 is still limited by the not yet fully evaluated light shift from the free running optical lattice laser operated near the magic wavelength. We are currently improving our transportable system to reach an uncertainty at or below the 10^-17 level, which will finaly be limited by the uncertainty in blackbody radiation shift correction.