Within the AEgIS project, the team of scientists has managed to cool down a sample of positronium with laser light and thus open up the way to new research on antimatter. The experiment was described in an article published in "Physical Review Letters".

The aim of the AEgIS experiment was to precisely measure the acceleration with which a neutral atom of antihydrogen falls in Earth’s gravity, as well as to check the so-called weak equivalence principle (free fall of a body does not depend at all on its mass, composition or internal structure) for objects built of antimatter.

As described by CERN in a release on the publication, to create antihydrogen, so a positron orbiting around an antiproton, AEgIS directs a beam of antiproton produced and slowed down in a so-called Antimatter Factory towards the positronium cloud, which are atoms composed of an electron and a positron. The cloud is created by placing positrons in nanoporous silica – circa one in three positrons makes up a positronium. If the antiproton and positronium meet, the positronium gives its positron to the antiproton creating antihydrogen.

Cooling with a laser

This way of creating antihydrogen means that scientists can also study positronium. Its very short lifespan is, however, a problem, since it falls apart into gramma rays within 142^nd billion of a second. Despite this disadvantage, its simple composition causes that it is very attractive in terms of research since it allows to search for new physical phenomena with greater precision. This however, requires extreme cooling of the positronium sample.

The success of the article’s authors consists of decreasing the temperature of this sample from 380 to 170 degrees Kelvin. For this purpose, the researchers used an atypical laser (a broadband one) which can cool a larger part of the sample.

Moreover, the team’s research may enable to conduct highly accurate measurements of  matter-antimatter systems, which in turn can uncover principles of new physics. In the long-term, the AEgIS experiment might result in development of a gamma radiation laser, a new tool to be used in fundamental and application research.

Role of WUT experts

– The Warsaw University of Technology team has contributed to modernisation of the experiment control system, implementing open software Sinara/ARTIQ and a solution based on open equipment instead of tailor-made electronics – says Professor Georgy Kornakov, from the Faculty of Physics, leader of the WUT scientists team in the AEgIS-PL scientific Consortium (with IF-PAN and UMK). – The control system is used to service the various parts of the equipment and to plan series of experiments. Our group also took part in creating an online visualisation and development of a data processing platform.

The WUT AEgIS team consists of specialists from the Faculty of Physics, Faculty of Electronics and Information Technology and Faculty of Electrical Engineering and seven students. The work of the group is led by Professor Kornakov, who at present is also coordinator of the programme of antiproton atoms in the AEgIS experiment.

The article "Positronium laser cooling via the 13S-23P transition with a broadband laser pulse" can be read on the website of "Physical Review Letters".