Antimatter- from Physics to Application. Professor Mike Charlton, Physics Colloquium 08 03 2023

The topic of antimatter is introduced by recalling its prediction and discovery in the 1930’s, and a brief history of the subject is given. Positrons have since found numerous applications in atomic and materials science, engineering and medicine, often based upon their annihilation with electrons, their matter equivalent particle. What makes this antiparticle useful as a probe is discussed, and examples described.

More recently, physicists working at CERN have learnt how to create atoms of antihydrogen, the positron-antiproton bound state, under controlled conditions in vacuum and capture some of them in a magnetic minimum neutral atom trap. They can be held therein for many hours and subject to laser and microwave radiation to probe transitions of the anti-atom. Aspects of the experiments are described, and some of the latest results presented. We also discuss the motivation for undertaking such experiments, which will involve one of nature’s great conundrums: the absence of bulk antimatter in the current epoch of the Universe.