Detector Configurations for Equivalence Principle Tests with Strong Separation of Signal from Noise

Abstract - Testing the Equivalence Principle (EP) at a level of accuracy substantially higher than the present state of the art requires resolving a very small signal out of the instrument’s intrinsic noise and also the noise associated with the instrument’s motion and gravity gradients. In the test of the Equivalence Principle in an Einstein Elevator under development by our team, the acceleration detector spins about a horizontal axis while free falling for about 25 s inside a comoving capsule released from a stratospheric balloon. The characteristics of the instrument package and the configuration of the detector itself play a key role in the ability to extract an EP signal at the desired threshold level out of dynamics-related noise. Numerical simulations of the detector’s dynamics in the presence of relevant perturbations, having assumed realistic errors and construction imperfections, show the merits of the detector configuration selected. The results illustrate that the effects of dynamics and gravity gradients, near or at the signal frequency, can be limited to levels smaller than the expected threshold sensitivity of the detector.