A compact laser-pumped Rb clock with 5×10−13 τ−1/2 frequency stability

We have realized a compact, laser-pumped Rb atomic frequency standard in view of next generation space applications. The clock's Physics Package has a volume of 1.1 liters, and includes a frequency-stabilized diode laser and 2 clock resonator packages. The measured clock short-term stability is 5×10^-13 τ^-1/2, reaching <; 3×10^-14 at τ > 20'000s. The typical clock drift is 2×10^-13/day, on the same level as the drift observed for a modified GALILEO RAFS operated with laser pumping under vacuum.