Germany's PTB Upgrades Cesium Atomic Clock AWG Control System, Adds Sequence Restart Mode

en.Wedoany.com Reported - On September 16, Spectrum Instrumentation of Germany announced the latest application of its arbitrary waveform generators (AWG) in the upgrade of the cesium fountain atomic clocks at the Physikalisch-Technische Bundesanstalt (PTB). PTB has integrated Spectrum M4x.6622-x4 PXIe-format AWG cards into the CSF1 and CSF2 cesium fountain clocks, replacing part of the original custom analog control circuits with a digital waveform generation system to provide RF signals for laser cooling, atomic launching, and state detection processes. CSF1 and CSF2 jointly participate in maintaining Germany's national reference time scale UTC(PTB).

PTB's cesium fountain clocks use the ground-state transition of cesium-133 atoms as the frequency reference. During operation, cesium atoms are first cooled to the microkelvin level by means of a magneto-optical trap or optical molasses, and then launched upward by laser. The atomic cloud passes through the Ramsey microwave cavity twice during its ascent and descent, and the system locks the atomic resonance frequency by measuring the transition probability. A single complete measurement cycle takes approximately 1.2 seconds and operates continuously 24 hours a day.

The core device of this upgrade, the M4x.6622-x4, is responsible for generating the RF waveforms needed to drive the acousto-optic modulators, thereby controlling the laser frequencies used in the cesium atom cooling, launching, and detection stages. PTB previously used custom analog electronic systems for these controls. As long-term operation and maintenance requirements increased, the research team began migrating the relevant control chains to a digital AWG architecture.

During system integration, PTB proposed that each laser needed to invoke a specific waveform sequence at different operating stages of the atomic clock, and the original AWG operating mode could not directly meet this timing requirement. Spectrum subsequently developed Sequence Restart Mode for the M4x.6622-x4, enabling the waveform sequence to be restarted according to external control requirements and synchronized with the fountain clock's operating cycle. After development, this function has been tested on the PTB system.

Spectrum has extended Sequence Restart Mode to its 65xx and 66xx series AWGs and is providing it free of charge to existing users through the latest driver. The 65xx and 66xx series belong to Spectrum's high-speed arbitrary waveform generator product line and can be used to generate multi-channel RF and complex waveform signals; this newly added operating mode was driven by the actual control requirements of PTB's atomic clocks.

PTB's two cesium fountain clocks are not only used for Germany's legal time generation, but also participate in global atomic clock data comparison and the establishment of International Atomic Time. The laser control, microwave excitation, and timing systems required for atomic clock operation all need to work continuously over the long term, and this AWG upgrade mainly targets the laser RF control link among them.