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NPL supplies caesium fountain primary frequency standards to other national standards laboratories or organisations needing direct reference to a realisation of the SI second, such as time distribution centres and large scientific facilities. The standard is also useful to observatories which require precise timing for astronomical observations and satellite laser ranging.
NPL recently installed a caesium fountain clock at CERN for their ALPHA experiment, and visited by NPL’s Dr Peter Thompson, CEO, Dr Emma Haynes, Partnership Director and Dr Leon Lobo, Head of NTC. 
ALPHA (Antihydrogen Laser Physics Apparatus) is an international collaboration based at CERN, working with trapped antihydrogen atoms, the antimatter counterpart of the simplest atom, hydrogen. Their mission is to use ultra-precise spectroscopy to uncover, as yet unseen, differences between matter and antimatter.
The ultimate goal is to measure the energy level structure of the antihydrogen system when excited with lasers. This has been successful achieved by the collaboration in the past however the precision of the measurement will soon be limited by the knowledge of the frequency of the laser applied during the experiment.
The caesium fountain will support ALPHA to determine the frequency of light absorbed by antihydrogen (hydrogen’s antimatter counterpart) with the same accuracy as has already been achieved for hydrogen. This is vital to understanding the extent of the symmetry between matter and antimatter, a big question at the heart of how the Universe works.
The UK is a key partner in ALPHA and the capability provided by the caesium fountain reinforces the UK’s status as a global leader in the field of low-energy antimatter research.
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15 Nov 2023