Measuring GBAR with emulsion detector

The motivation of the AEgIS experiment is to test the universality of free fall with antimatter. The goal is to reach a relative uncertainty of 1% for the measurement of the earth's gravitational acceleration $\bar{g}$ on an antihydrogen beam. High vertex position resolution is required for a position detector. An emulsion based detector can measure the annihilation vertex of antihydrogen atoms with a resolution of 1-2 μm, which if realized in the actual experiment will enable a 1% measurement of $\bar{g}$ with less than 1000 $\bar{H}$ atoms. Developments and achievements on emulsion detectors for the AEgIS experiment are presented here.