New Test of the Gravitational Inverse-Square Law at the Submillimeter Range with Dual Modulation and Compensation

By using a torsion pendulum and a rotating eightfold symmetric attractor with dual modulation of both the interested signal and the gravitational calibration signal, a new test of the gravitational inverse-square law at separations down to 295 mu m is presented. A dual-compensation design by adding masses on both the pendulum and the attractor was adopted to realize a null experiment. The experimental result shows that, at a 95% confidence level, the gravitational inverse-square law holds (vertical bar alpha vertical bar <= 1) down to a length scale lambda = 59 mu m. This work establishes the strongest bound on the magnitude alpha of Yukawa-type deviations from Newtonian gravity in the range of 70-300 mu m, and improves the previous bounds by up to a factor of 2 at the length scale lambda approximate to 160 mu m.