| According to the Newtonian Law of Universal Gravitation, the strength of thegravitational force between two point bodies falls as the inverse-square of the distance between them. Recently, novel new theoretical scenarios, inspired by string or M theory, predict possible violations of this inverse-square behavior with test mass separations below 1 mm.Motivated by these theories, we are currently endeavored to test the gravitational inverse-square law at separations ranging down to 100μm. To maximize the masses that can be brought to distances of 100μm, flat disk geometry is used for both the source and test masses, which can also greatly suppress Newtonian forces relative to new short-range effects. We have constructed a capacitive sensor system with the angular detective sensitivity of at least 1 x 10-6rad. With help of the capacitive sensor system and the six freedoms platform which has a resolution of 1 μrad for the circle goniometer and 0.05μm for the linear segment, we thus can precisely control the gesture of the source mass. Feedback control was used to maintain the torsion balance in its initial equilibrium state through the parallel capacitive plates. A thin conducting plate is inserted between the test and source masses and acts as electrostatic shield.This work is partially supported by the National Project for the Development ofKey Fundamental Science in China (2003CB716305), and the National Natural Science Foundation of China (NSFC: 10121503)... |
