Capacitance Alignment for Future Yukawa Interaction Experiment

Yukawa-like interactions arising from hypothetical new bosons are poorly constrained below 1 μm. Using a 500 μm long cylinder with a radius of 150 μm instead of a spherical test mass, we will further improve the limits on Yukawa-like interactions in the sub-micron regime by an order of magnitude. However, to perform a successful experiment the orientation of the cylindrical test mass with respect to a planar source mass needs to be determined to within 3 nm. A scheme is being developed to use the capacitance between the cylinder and the planar source mass to determine the cylinder's relative position and orientation. The method is currently being tested on a scaled up system comprising a 5 cm long brass cylinder with a diameter of 5 cm, standing in for the test mass, and a brass plate acting as the planar source mass. On this scale the position needs to be known to within 1000 nm and the angle to within 100 μrads to ensure that in the final application the position is known to within 3 nm and the angle to within 1 μrad. The strategy involves comparing actual capacitance measurements to capacitance values obtained from a COMSOL simulation with the cylinder in different positions. In this presentation I will show the progress made in using capacitance as an alignment indicator.