Laser-cooled Be+ for improved antihydrogen trapping and magnetometry


We have laser-cooled beryllium ions in a Penning-Malmberg trap dedicated for antihydro-gen formation. This trap is combined with a magnetic minimum trap to confine antihydrogen.This can be used to assist in the studies of antihydrogen in two distinct ways. The first appli-cation of the cold9Be+is to sympathetically cool positrons, which are used for antihydrogenformation. With this assistance we expect to produce colder antihydrogen and ultimatelyenhance the trapping rates of antihydrogen inside a magnetic trap by at least an order ofmagnitude. This would greatly improve measurements of antihydrogen properties allowingfor increased precision. Cold Be+could also be used for in-situ measurements of magneticfields in our antihydrogen traps. The method proposed in this work is to measure an elec-tron spin-flip transition frequency in the ground state of Be+, which is highly sensitive tothe external magnetic field strength. The electron spin-flip transition could be induced bymicrowave radiation and detected via fluorescence from laser-cooling transition. Magnetom-etry plays a crucial role in trapped antihydrogen research, especially for antimatter gravitymeasurement performed at high magnetic fields. Also, with increasing precision of the an-tihydrogen spectroscopy measurements, the uncertainty of the magnetic field will increasethe contribution to the systematic errors. Additionally, the benefit of using electron spin-flip in Be+is that it could be used to characterise the strength of the microwaves inside theALPHA-2 trap. In this work, the feasibility of magnetometry using9Be+inside the ALPHA’sPenning trap was studied. The microwave induced electron spin-flip in Be+was observed forthe first time within the ALPHA apparatus. The uncertainty of the external magnetic fieldderived from this proof-of-principle measurement was comparable to the currently usedElec-tron Cyclotron Resonancemethod and there are prospects for significant improvement. Thelaser-cooling procedure was improved, which should allow further study with sympatheticcooling of positrons and application of this technique to antihydrogen production sequence.

Joanna Peszka

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