AEgIS at ELENA: outlook for physics with a pulsed cold antihydrogen beam

Abstract

The efficient production of cold antihydrogen atoms in particle traps at CERN's Antiproton Decelerator has opened up the possibility of performing direct measurements of the Earth's gravitational acceleration on purely antimatter bodies. The goal of the AEgIS collaboration is to measure the value of for antimatter using a pulsed source of cold antihydrogen and a Moiré deflectometer/Talbot-Lau interferometer. The same antihydrogen beam is also very well suited to measuring precisely the ground-state hyperfine splitting of the anti-atom. The antihydrogen formation mechanism chosen by AEgIS is resonant charge exchange between cold antiprotons and Rydberg positronium. A series of technical developments regarding positrons and positronium (Ps formation in a dedicated room-temperature target, spectroscopy of the=1-3 and =3-15 transitions in Ps, Ps formation in a target at 10 K inside the 1 T magnetic field of the experiment) as well as antiprotons (high-efficiency trapping of [Formula: see text], radial compression to sub-millimetre radii of mixed [Formula: see text] plasmas in 1 T field, high-efficiency transfer of [Formula: see text] to the antihydrogen production trap using an in-flight launch and recapture procedure) were successfully implemented. Two further critical steps that are germane mainly to charge exchange formation of antihydrogen-cooling of antiprotons and formation of a beam of antihydrogen-are being addressed in parallel. The coming of ELENA will allow, in the very near future, the number of trappable antiprotons to be increased by more than a factor of 50. For the antihydrogen production scheme chosen by AEgIS, this will be reflected in a corresponding increase of produced antihydrogen atoms, leading to a significant reduction of measurement times and providing a path towards high-precision measurements.This article is part of the Theo Murphy meeting issue 'Antiproton physics in the ELENA era'.

Stimulated decay and formation of antihydrogen atoms

“…The high laser intensity required, especially for the single-step srr, can raise the question of using pulsed stimulated radiative recombination that would have also the advantage to produce antihydrogen in a pulsed manner. This can be useful for further manipulations using pulsed fields and for experiments requiring a time-of-flight measurement [62]. Due to the lower duty cycle, the production rate would be smaller, however the saturated power will be very easily reached and direct stimulation down to the 2p-state would be feasible.…”

Positronium Physics and Biomedical Applications

“…To measure the effect of gravity on antimatter, on the one hand o-Ps in excited states is being used by two experiments at CERN's Antiproton Decelerator, AEgIS (Doser et al, 2018) and GBAR (Dufour et al, 2015;Perez and Sacquin, 2012), as an intermediate tool to produce antihydrogen via a charge-exchange reaction with antiprotons (Amsler et al, 2021). The goal of these experiments is to measure the acceleration experienced by antihydrogen in the gravitational field of the earth.…”

“…Rare decays are strongly constrained by precision measurements of the electron anomalous magnetic moment and electric dipole moment with a prime topic being the search for invisible decays in connection with possible dark matter candidates called "mirror matter" particles (Vigo et al, 2020). In connection with gravitation, positronium is also playing an important role in precision tests of gravity on antimatter planned at CERN, the experiments AEgIS (Doser et al, 2018) and GBAR (Dufour et al, 2015;Perez and Sacquin, 2012).…”

Laser cooling of antihydrogen atoms

“…Techniques have been developed to produce 15 – 18 , confine 19 – 21 and interrogate cold antimatter atoms with microwaves 13 , 22 and lasers 10 – 12 , 23 . In addition, experiments are being built to measure the gravitational properties of antimatter 14 , 24 , 25 . The finite kinetic energies of the anti-atoms impose substantial limitations on the precision of many of these measurements.…”