Apparatus for measuring the thermal Casimir force at large distances

TL;DR

This paper proposes a novel Casimir measurement setup using a differential force method with a semi-transparent over-layer, enhancing the ability to distinguish thermal Casimir forces and reduce electrostatic interference at large distances.

Contribution

It introduces a new apparatus design that amplifies differences between theoretical models and mitigates electrostatic effects, enabling clearer observation of the thermal Casimir force at micrometer scales.

Findings

Amplifies differences between Drude and plasma models.

Reduces electrostatic patch effects.

Enables measurement of thermal Casimir force up to several microns.

Abstract

We describe a Casimir apparatus based on a differential force measurement between a Au-coated sphere and a planar slab divided in two regions, one of which is made of high-resistivity (dielectric) Si, and the other of Au. The crucial feature of the setup is a semi-transparent plane parallel conducting over-layer, covering both regions. The setup offers two important advantages over existing Casimir setups. On one hand it leads to a large amplification of the difference between the Drude and the plasma prescriptions that are currently used to compute the thermal Casimir force. On the other hand, thanks to the screening power of the over-layer, it is in principle immune from electrostatic forces caused by potential patches on the plates surfaces, that plague present large distance Casimir experiments. If a semi-transparent conductive over-layer with identical patch structure over the Au-Si regions of the plate can be manufactured, similar to the opaque over-layers used in recent searches of non-newtonian gravitational forces based on the isoelectronic technique, the way will be paved for a clear observation of the thermal Casimir force up to separations of several microns, and an unambiguous discrimination between the Drude and the plasma prescriptions.