Simulation of a Low-Energy Hydrogen Ion Beamline for the ALPHA Antihydrogen Experiment

Abstract

The universal imbalance between matter and antimatter stands as one of the great unfilled gaps in the body of human knowledge. According to the standard model, the matter created in the Big Bang should have appeared as matter and antimatter in equal amounts, and consequently should have devolved almost entirely back to energy with the cooling of the universe. This is demonstrably wrong. Behind dark energy and dark matter, the observable universe is dominated in all directions by baryonic matter uncontested by the antimatter we expect to see. To explain this, the scientific community performs experiments of every observable metric on cold, trapped antiparticles in the hopes of discovering some fundamental discrepancy between matter and antimatter. The ALPHA collaboration is one such experiment, creating trapped samples of antihydrogen out of cold antiproton and positron plasmas. In 2023, it made the first direct measurement of antihydrogen's interaction with gravitational fields using the ALPHA-g experiment - the newest addition to an expanding list of publications leading back to the first trapped antihydrogen. As ALPHA-g prepares for further testing and the laser spectroscopy experiment ALPHA-2 prepares for an ugrade to ALPHA-3, ALPHA has turned its eye towards even more precision in its matter-antimatter comparisons. It is hoped that if the properties of hydrogen can be measured in ALPHA's antihydrogen traps, the two might be compared with ever higher degrees of precision. This thesis describes the structure and simulation of a new addition to ALPHA, which would allow the integration of charged particle sources. In this thesis, numerical models of pulsed charged particle beams from a hydrogen ion source are tracked from the source, through the new injector module, to end in ALPHA's experiments. The overall performance of the new module is appraised, and results are compared to prior simulations of specific segments of the module. Special attention is given to the steering system used to to guide the beams into the preexisting ALPHA beamline, which had not yet been modeled. The steering region is tested for all its modes of operation, several varieties of hydrogen ion, and changing beam energy. It is shown that the injector module is capable of delivering trappable ions to both ALPHA experiments, but that bunch lengthening along the path of the beam may prevent all delivered particles from being captured. Several areas of interest are noted which preliminary analysis indicates may be used to shorten the length of the delivered particle bunches, thereby increasing the number of trappable ions.

Date of Award	1 Aug 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Stewart Boogert (Supervisor) & William Bertsche (Supervisor)