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Be+-Assisted Antihydrogen Synthesis and Trapping / MARIA GONCALVES
Swansea University Author: MARIA GONCALVES
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Copyright: the author, Maria Beatriz Gomes Gonçalves, 2026.
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DOI (Published version): 10.23889/SUThesis.71615
Abstract
Antihydrogen, the bound state of a positron and an antiproton, is a uniquely well-suited system for testing fundamental symmetries between matter and antimatter. The Antihydrogen Laser Physics Apparatus (ALPHA collaboration) synthesises antihydrogen atoms by slowly merging cold non-neutral positron...
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Swansea
2026
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Madsen, N. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa71615 |
| Abstract: |
Antihydrogen, the bound state of a positron and an antiproton, is a uniquely well-suited system for testing fundamental symmetries between matter and antimatter. The Antihydrogen Laser Physics Apparatus (ALPHA collaboration) synthesises antihydrogen atoms by slowly merging cold non-neutral positron and antiproton plasmas and traps the antiatoms in a magnetic minimum trap.While trapping efficiency has improved since its first demonstration in 2010, it plateaued after 2017.In ALPHA’s experimental conditions, antihydrogen is predominantly formed via three-body recombination, which has been theoretically and experimentally shown to strongly depend on the temperature of the positron plasma: lower positron temperatures yield higher antihydrogen trapping rates. In the ALPHA-2 trap, positrons alone reach a lower temperature limit of 15−20 K.The implementation of sympathetic cooling of positrons through collisions with laser-cooled Be+ions enabled stable lowering of these temperatures to below 10 K.This thesis describes the work towards antihydrogen synthesis with positrons prepared using this cooling method. A novel ion plasma preparation technique was developed to improve reproducibility, and a sophisticated control system with automated beam steering was implemented to ensure long-term operational stability. Moreover, the first demonstration of sympathetic cooling of positrons to < 10 K in a radially asymmetric magnetic field was carried out. Culminating in the first Be+-assisted antihydrogen synthesis and trapping. Careful optimisation of this technique resulted in a near eightfold increase in the antihydrogen trapping rate, and allowed for systematic studies of three-body recombination that were not possible before its implementation. Overall, this technique represents a paradigm shift for the ALPHA physics programme and provides a deeper understanding of antihydrogen synthesis, opening new avenues for precision studies of antimatter. |
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| Keywords: |
Physics, Antimatter Physics, Atomic Physics |
| College: |
Faculty of Science and Engineering |