Sensitivity of emulsion detectors to low energy positrons

Nuclear emulsions are a formidable tool for detecting charged particles with sub-micrometric spatial resolution, a feature which is essential in quantum interferometry experiments with antimatter. In this context, we have tested the sensitivity of such a detector, devoid of the usual protective layer, with very low energy positrons, that is in the range 0.2-17 keV. The results show that emulsions are sensitive to positrons with energy below 1 keV. Their detection efficiency increases as a function of the energy and it tends to saturate over ∼15 keV. This demonstrates the feasibility of using this type of detector in low energy regime and defines the limits of use for future gravitational studies with antimatter.