Extended Data Fig. 6: Simulation of electrostatic coupling.

Our finite-element simulation of the electrostatic interaction of a charged test mass (10⁵e⁺) and a grounded source mass was validated using the analytical method described in ref. ⁵⁶. When inserting a 150-μm-thick, conductive electrostatic shield between them, the electrostatic force exerted onto the test mass is dominated by the test mass–shield interaction, that is, it becomes independent of the source-mass position. Residual fluctuations of the force are on the 3–10% level of gravity, without a clear source position dependence, and are expected to stem from numerical errors.