NTSC SrII optical lattice clock with uncertainty of 2x10-18

Abstract We report the systematic evaluation of the SrII optical lattice clock at the National Time Service Center (NTSC), achieving an uncertainty of $\rm{1.9\times10^{-18}}$. The newly established $^{87}$Sr optical lattice clock controls the black-body radiation shift by moving atoms into a temperature-stabilized chamber for clock transition detection. It mitigates the DC Stark shift by using conductive optical films on the inner windows, and reduces both the density shift and AC Stark shift by operating the clock with a relatively low lattice trap depth. Additionally, this clock accommodates changes in the angle between the lattice and gravity directions by rotating the entire setup, allowing for convenient adjustment of the tunneling effect in the shallow lattice.