Frequency reference

Active hydrogen maser with supply electronics sitting in MPQ's clock room.

Active hydrogen maser with supply electronics sitting in MPQ's clock room.

We maintain an active hydrogen maser whose correct operation is monitored using a global positioning system (GPS) receiver. The complete system is connected to an uninterruptible power supply and is located an a quiet room with very good temperature stability. We calibrate the maser by comparing it with the time signals broadcasted by the GPS. Comparing our data with similar data generated at the Physikalisch Technische Bundesanstalt at Braunschweig (PTB) allows us to calibrate our maser relative to the PTB clocks. A frequency comb is used to convert the masers reference frequency into the optical. A fiber network is used for distribution among the institute.

The portable cesium fountain microwave clock FOM of the Observatoire de Paris was operating in MPQ's clock room during the absolute frequency measurement in June 2010.

The portable cesium fountain microwave clock FOM of the Observatoire de Paris was operating in MPQ's clock room during the absolute frequency measurement in June 2010.

For the absolute frequency measurement, we have been relying on the transportable cesium fountain microwave clock FOM of the Observatoire de Paris. Future experiments will benefit from a long-haul optical fiber link for clock synchronization between our Garching laboratory and the stationary microwave and optical atomic clocks at the PTB in Braunschweig that is now being implemented within a collaboration led by the PTB.