Antihydrogen from non-neutral plasmas

Antihydrogen, the bound state of a positron and an antiproton, calculable from first principles, is a uniquely well suited system for searching for discrepancies between matter and antimatter that could explain the baryon asymmetry of the universe.



The ALPHA collaboration synthesises and traps antihydrogen atoms using cold non-neutral plasmas of positrons and antiprotons [1]. This decade long effort has allowed the first detailed studies of internal states [2, 3].



The ability to trap anti atoms has evolved significantly since the first demonstration in 2010, such that we now not only trap the anti-atoms, but continuously accumulate them over many hours [4]. Additional techniques (e.g. [5]) have allowed accumulating many thousands of anti-atoms at rates of more than a thousand atoms per hour. The ALPHA experiment is thus uniquely suited to continue to expand our multi pronged experiments on antihydrogen.



These developments, together with the recent addition of laser-cooling [6] to the toolkit will allow us to probe the internal structure of antihydrogen to even greater precision that we’ve accomplished so far, and start detailed, eventually direct, comparisons with hydrogen as well as continue evolving our gravitational measurements of antihydrogen [7].



Here we focus on some of the key non-neutral plasma techniques we have developed to have thousands of anti-atoms available for study, and highlight some of our most interesting measurements to date.