The leading science journal Nature has published details of a breakthrough in a major international experiment to study anti-matter closely for the first time.
The report, entitled “Trapped Anti-hydrogen”, details how scientists – including a team from Swansea University’s Department of Physics – working on the collaborative ALPHA (Anti-hydrogen Laser PHysics Apparatus) project at CERN, the European Organisation for Nuclear Research, in Geneva, have reached a significant milestone by successfully trapping and holding atoms of anti-hydrogen.
Professor Mike Charlton, who leads the Swansea team, said: “Every type of particle has its anti-matter equivalent which is its mirror image in terms of having, for instance, the opposite electrical charge.
“Because hydrogen is the simplest of all atoms, anti-hydrogen is the easiest type of anti-matter to produce in the laboratory. By studying it for the first time, we will be able to understand its properties and establish whether it really is the exact mirror image of hydrogen.
“That understanding will hopefully enable us to shed light on exactly why almost everything in the known Universe consists of matter, rather than anti-matter, and what the implications are in terms of the fundamental way the Universe functions.”
The ALPHA project involves Professor Mike Charlton, Dr Niels Madsen, Dr Dirk Peter van der Werf and Dr Stefan Eriksson from Swansea University, who work closely with physicists at the University of Liverpool, led by Professor Paul Nolan. The work is supported by the Engineering and Physical Sciences Research Council (EPSRC).
Scientists have been able to undertake the controlled production of anti-hydrogen atoms in the laboratory for nearly a decade; a breakthrough which Swansea University physicists played a key role in as part of the ATHENA project, the first experiment to produce copious amounts of cold antihydrogen, which was also based at CERN.
But as anti-matter particles are instantly annihilated when they come into contact with matter, it has not previously been feasible to study anti-hydrogen atoms in any detail.
The ALPHA team has developed techniques that not only cool and slow down the anti-particles that make up anti-hydrogen and gently mix them to produce anti-hydrogen atoms, but also trap some of the anti-atoms for long enough so that they can be studied.
A key advancement has been a new method that allows the cooled anti-particles to be brought together in a way that ensures the anti-hydrogen atoms are cold enough to be trapped.
Careful handling and cooling of the particles is essential to this breakthrough as the state-of-the-art ALPHA magnetic trap can only hold atoms with an energy a 100 billion times lower than that of the particles delivered by CERN.
Another key instrument is a detector, which allows scientists to identify the disintegration of individual anti-protons in the apparatus. The ability to detect individual events has been crucial. Published results report 38 trapped anti-hydrogen atoms have been observed by release and disintegration in 335 experiments.
“This development is a kind of experimental paradigm shift,” said Swansea University Physicist Dr Niels Madsen.
“Having trapped anti-hydrogen atoms brings measurements that seemed like wishful thinking only a few months ago much closer to realisation. We are already gearing up for the first simple tests.”
Dr Madsen, who is currently on sabbatical at CERN after winning a prestigious Royal Society Leverhulme Trust Senior Research Fellowship, added: “Our ability to release the particles in a few tens of milliseconds by turning our complex magnetic trap off has been an essential component in our success.”
To view the “Trapped Anti-hydrogen” article visit www.nature.com.
