Positron accumulation in the GBAR experiment

We present a description of the GBAR positron (e+) trapping apparatus, which consists of a three stage Buffer Gas Trap (BGT) followed by a High Field Penning Trap (HFT), and discuss its performance. The overall goal of the GBAR experiment is to measure the acceleration of the neutral antihydrogen (H) atom in the terrestrial gravitational field by neutralising a positive antihydrogen ion (H+), which has been cooled to a low temperature, and observing the subsequent H annihilation following free fall. To produce one H + ion, about 1010 positrons, efficiently converted into positronium (Ps), together with about 107 antiprotons (p), are required. The positrons, produced from an electron linac-based system, are accumulated first in the BGT whereafter they are stacked in the ultra-high vacuum HFT, where we have been able to trap 1.4(2) x 109 positrons in 1100 s.

Automated summary

The article presents a description of the GBAR positron trapping apparatus, which aims to measure the acceleration of neutral antihydrogen atom in Earth's gravitational field by neutralizing a cooled positive antihydrogen ion. The apparatus requires a large number of positrons and antiprotons to produce one antihydrogen ion, which are trapped and accumulated in stages for further study.