Improving short and long term stability of pulsed optically pumped vapor cell frequency standards

In this paper we discuss how to improve both short and medium-long term frequency stability of a vapor cell frequency standard working in pulsed regime. We propose in particular a multi-step pumping technique that is able to put almost all the atoms in one of the two clock levels, increasing in this way the signal-to-noise ratio with respect to the usual optical pumping made with a single laser pulse. Moreover, we discuss the phenomena affecting the medium-long term frequency stability and how it is possible to control them, making the overall clock stability compatible with sigma_y(tau) =3x10^-13 tau^-frac12 for integration times up to tau = 10⁵ s.