Testing the equivalence principle on a trampoline

We are developing a Galilean test of the equivalence principle in which two pairs of test mass assemblies (TMA) are in free fall in a comoving vacuum chamber for about 0.9 s. The TMA are tossed upward, and the process repeats at 1.2 s intervals. Each TMA carries a solid quartz retroreflector and a p ayload mass of about one-third of the total TMA mass. The relative vertical motion of the TMA of each pair is monitored by a laser gauge working in an optical cavity formed by the retroreflectors. Single-toss precision of the relative acceleration of a single pair of TMA is 3.5 x 10(-12) g. The proj ect goal of Deltag/g = 10(-13) can be reached in a single night's run, but repetition with altered configurations will be required to ensure the corre ction of systematic error to the nominal accuracy level. Because the measur ements can be made quickly, we plan to study several pairs of materials.