Speaker
Description
The upgrade of the antiproton decelerator, the Extra Low ENergy Antiproton (ELENA) ring started its operation at CERN in the Fall of 2021 and opened a new era for antihydrogen research. The Gravitational Behaviour of Antihydrogen at Rest (GBAR) collaboration has since started taking data and aims to directly test the Weak Equivalence Principle with a free fall of ultracold antihydrogen $\mathrm{\overline{H}}$ in Earth's gravitational field. The main principle is to first produce an antihydrogen ion $\mathrm{\overline{H}^+}$ and sympathetically cool it with $\mathrm{Be^+}$ in a Paul trap to $\mathrm{\mu K}$ temperature. The excess positron is then photodetached using a $1640\,\mathrm{nm}$ laser and the now neutral anti-atom experiences a classical free fall. By measuring the time of flight and the annihilation position of the $\mathrm{\overline{H}}$ we want to measure its acceleration with a precision of $1\%$ in a first phase. During the production of the $\mathrm{\overline{H}^+}$, $\mathrm{\overline{H}}$ atoms, with a fraction in the 2S state, will be produced which can be used to measure the Lamb shift. I will present first evidence of $\mathrm{\overline{H}}$ production in 2022, a milestone for the experiment, as well as the status and future prospects of GBAR.
