Subsystems and design for a transportable cold ion microwave clock

High performance transportable microwave atomic clocks are enablers for resilient GNSS-free timescales. We present progress towards a transportable laser-cooled ytterbium ion microwave clock. This system incorporates our recently developed multi-ion trap chamber and redesigned electronics and optics systems, offering reductions in size, weight and power, with improved performance over our previous system. The benchtop prototype version of this clock uses the new physics package design and reaches a short-term instability of 1.2 × 10−12/√τ. We present the transportable clock design as well as subsystem test results, which so far indicate that a similar performance to the benchtop version is achievable in a 3U rack-mounted package.