%0 Generic
%A Zimmer, Christian
%C Heidelberg
%D 2021
%F heidok:31020
%R 10.11588/heidok.00031020
%T Experimental and Numerical Studies of Positronium Laser Cooling in a Magnetic Field
%U https://archiv.ub.uni-heidelberg.de/volltextserver/31020/
%X The present thesis deals with the application of techniques developed in the field of quantum optics to the exotic atom positronium (Ps), for the purpose of the preparation of cold ensembles of Ps atoms in a magnetic field.  The positronium atom, which describes the bound state between an electron and its own antiparticle, the positron, shows numerous peculiarities setting it apart from all other atoms which have been subject to laser cooling so far. In particular, its antimatter character as well as the extraordinarily small mass are accompanied by several unusual phenomena and, together with magnetic-field-induced effects, entail a highly complex laser cooling scheme. Due to the exotic properties, combined with the purely leptonic composition, cold and dense clouds of Ps atoms would represent an ideal testing ground for several fundamental theories and pave the way for many further fascinating applications, such as positronium Bose-Einstein condensation.  The conducted numerical simulations, which consider the full complexity of the scheme, reveal that a high cooling efficiency can be achieved with appropriate laser radiation in weak (|B| < 50 mT) and strong fields (|B| > 0.7 T) for many realistic experimental configurations. Based on these  results, Ps laser cooling has been realised experimentally within the AEgIS experiment at CERN. The measurements clearly demonstrate successful exertion of a symmetric optical force on the Ps ensemble in a field of |B| = 180 G, namely in the form of a significant population enhancement  in the centre of the velocity distribution, which represents a key feature of laser cooling as it is unambiguous evidence for laser-induced recoil effects.