Dr Benjamin (“Benji”) Rienaecker has been a Postdoc in my QUASAR Group since July 2022. He is one of the most passionate experimental researchers in the field of antimatter physics I have ever met and it is an absolute pleasure to work and discuss with him on some of the most challenging experiments.
Benji’s pioneering work on cold antimatter beams for precision research at the AEgIS experiment at CERN’s Antiproton Decelerator (AD) has many different facets: In his PhD, he investigated methods to form and manipulate cold positronium beams – which is absolutely essential for an efficient production of a beam of antihydrogen. He has also led the upgrade of the AEgIS positron source in 2020 whilst the experiment was connected to the new antiproton storage ring ELENA.
Benji’s contributions to AEgIS were essential for the first successful formation of a pulsed antihydrogen beam at AEgIS a few years ago. Just earlier this year, we successfully demonstrated positronium laser cooling in AEgIS which is widely recognized as a significant scientific breakthrough in the field. This success would not have been possible without Benji spending countless hours, days, nights and weekends in the experiment and the control room. Always keeping his eyes on the final and very challenging goals of the experiment.
Within AEgIS, Benji has been fantastic in bringing together a very diverse group of people, connecting researchers and students from many different institutions and countries at CERN. The scientific and technical advances that he helped enable now allow us to challenge fundamental principles, such as the universality of free fall, the Weak Equivalence Principle, and CPT invariance. This offers exciting prospects for unlocking a new understanding of physics beyond the standard model.
Benji’s many contributions to our group, and more widely to the field of antimatter physics, extend well beyond the laboratory space. For example, he has supervised a large number of summer students and interns at CERN with an almost unlimited enthusiasm. As an official CERN guide, he has also informed countless visitors about the complex challenges related to precision experiments. Thereby, he has engaged diverse audiences and promoted science more generally.
We have extremely ambitious research plans in AEgIS until (and beyond!) the end of this decade. I have no doubt that Benji’s work and creative ideas will continue to be crucial for the success of our collaboration. The 2024 Postdoc Appreciation Week gives me an excellent opportunity to thank Benj for his fantastic work and outstanding research.
Prof Carsten Welsch, University of Liverpool