Swansea University researchers Joos Schoonwater and Edward Thorpe-Woods with the new caesium fountain. Credit: Stefan Eriksson.

Swansea University researchers Joos Schoonwater and Edward Thorpe-Woods with the new caesium fountain. Credit: Stefan Eriksson.

A device that produces a fountain of caesium atoms could boost understanding of the Universe by measuring the frequency of light absorbed by antimatter.

Built in the UK with support from the Engineering and Physical Sciences Research Council (EPSRC), it has now been installed at the iconic CERN facility to support the pioneering Antihydrogen Laser Physics Apparatus (ALPHA) antimatter experiment.

Swansea University has led UK involvement in ALPHA, funded by EPSRC. Denmark’s Aarhus University has provided additional support, with funding from the Carlsberg Foundation.

The caesium fountain will help ALPHA 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 caesium fountain was designed and built at the National Physical Laboratory (NPL), the UK’s national metrology institute in Teddington, Middlesex.

The caesium fountain is enclosed in a case around two metres tall. Laser-cooled caesium atoms held in a vacuum chamber are launched up into a magnetically controlled tube before falling back down again.

Microwave radiation measures the frequency with which these atoms oscillate, to the fifteenth decimal place.

This will provide an ultra-accurate reference against which ALPHA can measure antihydrogen atoms’ interaction with laser light, enabling the frequency of light that antihydrogen absorbs to be determined.

The goal is to achieve a level of precision that represents a thousand-times increase compared with current knowledge. It is anticipated that this will be achieved within the next few years.

One of just a few of its kind in the world, this caesium fountain is unique in its reliability and robustness, crucial to withstanding the demands ALPHA will place on it.

Integrating the instrument with the experiment onsite avoids ALPHA having to access this kind of capability via satellite link, minimising inaccuracies in measurements taken.

The results will show whether, in-line with conventional theory, hydrogen and antihydrogen have exactly the same (though mirror-image) properties.

This could shed light on why there seems to be very little antimatter in the Universe today, even though it is generally held that equal amounts of matter and antimatter were created in the Big Bang 13.8 billion years ago.

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.

Jane Nicholson, Executive Director for Research Base at EPSRC said:

“This exciting device will further cement the UK’s role as a leading nation in the community of researchers studying the properties of antimatter.

"Providing superior accuracy to measure the frequency of light absorbed by antimatter, the atomic fountain clock demonstrates the importance of investment in world class facilities and the role they play in underpinning breakthrough discoveries and is an excellent example of academic and public sector research establishment collaboration.”

Professor Stefan Eriksson of Swansea University, who is leading ALPHA’s caesium fountain project, says:

“The new caesium fountain is essential to our continuing effort to determine if hydrogen and antihydrogen behave in the same way.

"Hopefully what we discover will enhance understanding of the basic building blocks of our Universe. The fountain will also help ALPHA benefit the UK by training researchers who can apply their skills – in instrumentation, for instance – to nationally important fields such as quantum technologies, which are anticipated to have a big impact on society.”

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