Test & measurement
EVOLUTION OF THE CLOCKS The caesium fountain clock requires careful control of the lasers. This was originally implemented using custom analogue circuitry developed by an earlier generation of PTB engineers and scientists. Maintaining such a complex system over the long term becomes increasingly difficult. So, like the experiment itself, the supporting electronics must evolve, leading Dr Rahm to explore how to replace its analogue system with a digital alternative. His research led him to integrate AWG (arbitrary waveform generator) cards in PXIe format from Spectrum Instrumentation. These cards generate the RF frequencies required to manipulate the laser frequencies for cooling, launching and detection of the atoms using acoustic-optic modulators.
RAPID RESPONSE FROM SPECTRUM’S SUPPORT TEAM
However, a challenge arose during implementation. Although the M4x.6622-x4 AWG cards met the accuracy requirements extremely well, none of the possible signal generation modes matched PTB’s specific requirements. For an efficient design of the caesium fountain clock cycle, each laser needs a specific set of waveforms at a specific point in the cycle. Dr Rahm contacted Spectrum Instrumentation’s support team, with support handled directly by the design engineers. In just two days, the software engineers developed a new feature called “Sequence Restart Mode”. Dr Rahm’s tests were successful, and the new mode works exactly as envisioned.
Dr Johannes Rahm inspecting the caesium fountain clocks, which run continuously 24 hours a day. (Photo courtesy of PTB)
Instrumentation Monthly October 2026
Spectrum Instrumentation has since released Sequence Restart Mode as a free-of-charge upgrade for all AWGs in the 65xx and 66xx series. The new mode can be enabled easily by installing the latest drivers.
Spectrum Instrumentation
www.spectrum-instrumentation.com
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