Speaker
Description
We have proposed a spectroscopic study of antihydrogen ($\mathrm{\bar{H}}$) Lamb shift using a neutral antiatomic beam at keV energies. Direct spectroscopy of the $n=2$ Lamb shift transition of $\mathrm{\bar{H}}$ atoms would enable the first measurement of the antiproton ($\bar{p}$) charge radius. Recently, the GBAR experiment demonstrated the production of 6.1 keV $\mathrm{\bar{H}}$ atoms via a charge exchange reaction of $\bar{p}$ passing through a positronium cloud, which can be utilized for Lamb shift spectroscopy. An experimental setup has been developed for the GBAR experiment.
The spectrometer comprises two consecutive microwave (MW) apparatuses and a Lyman-$\alpha$ photon detector. Each MW apparatus has a pair of parallel plate electrodes surrounded by a box to induce the Lamb shift transition. The detector counts the remaining $2S$ state $\mathrm{\bar{H}}$ atoms.
We present the development of MW apparatuses, their MW characteristics, and their commissioning using hydrogen atoms. Further, we discuss the expected precision in the Lamb shift spectroscopy for $\mathrm{\bar{H}}$ atoms.
