A capacitive detector to test the principle of equivalence in a free fall experiment

We describe a system of capacitive transducers applied to two free falling objects with the aim of detecting differential accelerations due to nonNewtonian components. The two objects have a cylindrical shape to minimize the systematic errors and they fall in a microgravity condition inside a vacuum tube released by a stratospheric balloon at an altitude of 40 km. The calibration of the capacitive transducers performed in laboratory has shown that it is possible to detect differential accelerations Δa ≲ 1.4 × 10−10 m s−2.