Laser-cooled ytterbium-ion microwave frequency standard

We report on the development of a trapped-ion, microwave frequency standard based on the 12.6 GHz hyperfine transition in laser-cooled ytterbium-171 ions. The entire system fits into a 6U 19-in. rack unit \((51\times 49\times 28\,\mathrm{{cm}})\) and comprises laser, electronics, and physics package subsystems. As a first step towards a full evaluation of the system capability, we have measured the frequency instability of our system which is \(3.6\times 10^{-12}/\surd \tau \) for averaging times between 30 and \(1500\,\mathrm{{s}}\).